Principles of Biology
Principles of Biology BIO 101
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Photosynthesis Photosynthesis Photosynthesis is the process by which organisms use the energy ofthe sun to synthesize organic compounds sugars from inorganic compounds CO2 and water Photosynthesis transforms the energy of the sun into chemical energy glucose 0 Provides the oxygen we breath removes C02 and provides food energy and shelter Photosynthesis Many organisms participate in photosynthesis Nearly all plants Some Protists Euglena kelp Some bacteria cyanobacteria Photosynthesis 6 6 6 Carbon dioxide Water Gucose Oxygen gas Photosynthesis Copyrlgh39 2099 Pearson Education lnc Carbon dioxide and water are waste products of cellular respiration Photosynthesis takes these products and converts them to the glucose and O2 necessary for cellular respiration Photosynthesis Photosynthesis occurs on a cellular level Chloroplasts are organelles which carry out photosynthesis Chloroplasts contain chlorophyll a light absorbing pigment which give autotrophs their distinctive color Photosynthesis Chloroplasts are concentrated in mesophyll the green tissue in the interior of a leaf Membranes in the chloroplast form the framework where many of the reactions of photosynthesis occur The Chloroplast 0 A chloroplast contains two membranes as do mitochondria 0 A thick fluid called the stroma fills the inner compartment ofthe chloroplast Suspended in the stroma are the thylakoids a system of interconnected membranous sacs which enclose another compartment known as the thylakoid space Chloroplast Outer and inner membranes Intermembrane Stroma Granum Thylakoid Space space Copynghl 2009 Fearsau Edunauon me The Chloroplast Built into the thylakoid membranes are the chlorophyll molecules that capture light energy Photosynthesis occurs throughout a plant all the green parts but is concentrated in the leaves 0 A plant will invest much of its energy into the production of its leaves in order to capture as much light energy as possible Make like a tree and Leaves are designed to capture light and increase the absorption of carbon dioxide Carbon dioxide enters the leaf and oxygen exits the leaf via the stomata tiny pores protected by guard cells 0 Water is supplied to the tree via its roots but may exit the leaves when the stomata are open a catch 22 why stomata open at night in many plants Pigments Pigments are light absorbing molecules built into the thylakoid membranes 0 Pigments absorb some wavelengths of light but reflect others We do not see the absorbed wavelengths because their energy has been absorbed by the pigment molecules we see the wavelengths that the pigment reflects Pigments 0 A leaf is green because chlorophyll absorbs colors other than green absorbs light most strongly in the blue and red but poorly in the green 0 Different pigments absorb different wavelengths Chloroplasts contain different types of pigments Increasing energy 4 105nm103nm 1nm 103nm 105nm 1m 103m I I I I I I I I I Gammal Xrays UV Infrared Micro Radio rays waves waves Visible light 380 400 500 600 700 750 Wavelength nm canyngme 2009 Pearson Educahmn we Pigments Chlorophyll a a type of chlorophyll pigment absorbs light mainly in the blue violet high energy and red low energy wavelengths Reflect Chloropl h Thylak0Id Autumn color change Autumn leaf color is a phenomenon that affects the normally green leaves of deciduous trees and shrubs changing to reds and yellows and various shades in between In late summer the veins that carry fluids into and out of the leaf are gradually closed off and chlorophyll decreases Autumn color change 0 In addition to chlorophyll other pigments known as accessory pigments are present in plants these include carotene and cyanins 0 When chlorophyll concentrations decrease at the end of summer some ofthese other pigments which are usually masked by chlorophyll reveal their colors Carotene for example is especially long lasting Photosynthesis Plants produce CO2 by splitting water Stable isotopes 180 and 16O of oxygen revealed that the 02 produced by plants originates from water H20 and not from CO2 Experiment 1 Not labeled Experiment 2 Labeled Photosynthesis Photosynthesis occurs in 2 stages each with multiple steps 1 Light reactions convert light energy into chemical energy and produce 02 2 Lightindependent reactions the Calvin Cycle assembles glucose molecules using CO2 carbon fixation and the energy rich products ofthe light reactions 1 Light dependent Reactions 0 Light reactions occur in the thylakoid membranes of the chloroplast 0 Water is split providing a source of electrons and giving off 02 as a by product H20 9 2H 12 02 2e39 Light energy absorbed by chlorophyll molecules is used to drive the transfer of electrons and H from water to NADP and generate ATP 1 Light dependent Reactions 0 Light reactions absorb solar energy and convert it to chemical energy NADPH Produces 02 as a by product No sugar is produced in light reactions 2 Lightindependent Reactions 0 Light independent reactions occur in the stroma of chloroplasts Consist ofthe Calvin Cycle which assembles sugar molecules using CO2 and NADPH The incorporation of Carbon from CO2 into organic compounds is called carbon fixation 2 Lightindependent Reactions 0 The Calvin Cycle does not require light but occurs during daylight hours when the light reactions power the cycle by supplying NADPH and ATP Often called quotdark reactions 0 NADPH provides the electrons to reduce Carbon from CO2 into glucose and ATP powers the cycle How do photosystems capture solar energy Pigments function by absorbing light energy and tranferring electrons to an energy shell farther from the nucleus quotexcited state 0 In the thylakoid membrane of the chloroplast chlorophyll passes off its excited electron to a neighboring molecule before it has a chance to drop back to its quotground state How do photosystems capture solar energy In the thylakoid membrane chlorophyll molecules are organized into clusters with other pigments and proteins called photosystems A photosystems consists of a number of light harvesting pigments bound to proteins surrounded by a reaction center complex How do photosystems capture solar energy 0 The pigments absorb light energy and pass the electrons energy from molecule to molecule until it reaches the reaction center The reaction center complex contains a pair of chlorophyll 0 molecules and an electron acceptor 0 There are 2 photosystems Photosystem II and Photosystem Photosystem Lightharvesting Reaction complexes center complex Primary electron acceptor Photon 39 Thylakoid membrane Transfer of energy Palr Of molecules Chlorophyll a molecules uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu nc Photosystems So how does this work 0 When light is absorbed by the pigments energy passes from pigment to pigment molecules until it reaches the reaction center of the photosystem where it excites an electron of chlorophyll to a higher energy state that is captured by the primary electron acceptor Photosystems 0 Water is split supplying its electrons to the chlorophyll molecule which lost its electrons to the primary electron acceptor releasing 02 as a by product Photosystems and II were named in order of their discovery but Photosystem functions first in the sequence of steps that make up the light reactions A mechanical analogy of the light reactions Electron transport chain Provides energy for synthesis of by chemiosm Photon Photosystem II Stroma Thylakoid space Canyngm 0 2m Pearson Euncahon Me Photosynthesis a review 0 Light reactions occur in the thylakoid membrane 2 photosystems capture solar energy which energizes electrons Photosystems transfer these excited electrons through electron transport chains which produces ATP and NADPH Water is split and O2 is released Photosynthesis a review 0 In the stroma ofthe chloroplast sugars are produced via the Calvin Cycle light independent reactions CO2 is reduced to form glucose Photosynthesis a review The sugar produced by plants during photosynthesis provides the starting materials to make structural components such as cellulose 50 of this sugar goes toward cellular respiration plants respire Photosynthesis a review Most plants make considerably more food each day than they need They stockpile this sugar as storing it in roots tubers and fruits sound familiar 0 Plants not only produce fuel for themselves but ultimately provide food for virtually all other organisms heterotrophs Global warming and the greenhouse effect r7 quot Global warming and the greenhouse effect 0 CO2 is an important greenhouse gas Greenhouse gases are gases in the atmosphere that absorb heat radiation 0 When solar radiation reaches the atmosphere visible light passes is absorbed by the planet s surface warming it Global warming and the greenhouse effect This heat is radiated back as longer infrared wavelengths which are absorbed by gases in the atmosphere reflecting some of the heat back to earth 0 Very important Without these greenhouse gases the Earth s surface temperature would be 33 C 59 F cooler than at present This process is called the greenhouse effect Increasing energy 10 5nm10 3nm 1nm 103nm 105nm 1m 103m I Gamma xrays UV i Infrared Micro Radio i rays ves waves Visible light Some heat energy escapes intqspace Global warming and the greenhouse effect C02 water vapor and methane are naturally occurring greenhouse gases Photosynthetic organisms absorb billions of tons of CO2 every year Most ofthis carbon returns to the atmosphere via cellular respiration but much of it remains locked in large tracts of forests and in long term storage as fossil fuels buried deep under the Earth s surface Global warming Since 1850 the start ofthe Industrial Revolution the concentration of CO2 in the atmosphere has increased 40 0 Increasing concentrations of CO has been linked to global warming a steady rise in Earth s surface temperature Earth s average surface temperature has increased by 12 14 F in the last 100 years Annual Average Global Surface Temperature Anomalies 18802006 Anomaly C relative to 19012000 06 JanDecGlobalMeanquot olalrllrIWTllVIllr over Land SI Ocean Ilr I I r r I T 08 l I l 1880 IIIIIIII 19001920 IIII 1940 I l I 1960 I l I I I 1980 2000 NCDCNESDlSNOAA 400 350 C02 ppm N20 ppb 250 Copyrighi v 2m P eeee an Ed uuuuuu 1 inc 500 Carbon Dioxide C02 Methane CH4 Nitrous Oxide N20 1000 Year 1500 2000 2000 1800 1600 1400 1200 1000 800 600 CH4 ppb Concentration of CO2 19582006 39 I 39 I 39 I 39 I r III 3 BBQ 39 msmgn SMpp Inm swamgraph r a 39 g 1973942005 MOM ESHLE39GMD 151quot I E 39 M 31 1 a If I W 39 3m m i v 1 39f I I g I f I r 1 o r39I39l j I g if39 I I1 I l I u g 1 I a 3211 l 214 Tf r 39 17 39 39 l l I I I 7 Global warming Rapid warming is changing the global climate TELLTJEKLE sums OF GLOBAL WARMING Sealevel se melting ice amp permafrost extreme weather events changing weather patterns Global climate change Global climate change affects biomes ecosystems communities and populations 0 The earlier arrival of warm temperatures in the spring is disrupting ecological communities What would happen if plants bloomed before their pollinators arrived What will happen to coral under increasing temperature How Cells Harvest Chemical Energy Cellular respiration is the process by which energy is harvested by cells from sugar Requires Oxygen 02 Releases Carbon Dioxide C02 water H20 and a large amount of ATP All of our cells harvest chemical energy from food Cellular Respiration stores energy in ATP molecules A cell uses energy to build and maintain its structure transport materials manufacture products move grow and reproduce Cellular respiration involves mainly sugars but other organic compounds can be broken down nearly all the equations you ll see use glucose as the representative food molecule Our bodies require a continuous supply of energy just to stay alive Organisms use energy from ATP for all its activities Breathing Heart pumping Maintainin g body temperatu re Thinking dreaming sxchuphoto437515 Organisms use energy from ATP for all its activities Above and beyond the energy we need for body maintenance cellular respiration provides energy for voluntary activities The amount of energy it takes to perform these activities are expressed as kilocalories a quotcaloriequot on a nutritional label actually equals 1 kilocalorie A kilocalorie is the quantity of heat required to raise the temperature of 1 kg water by 1 C The Calorie Connection The US National Academy of Sciences estimates that the average adult human requires 2200 kcal of energy per day maintenance voluntary activities Remember lipids provide twice as many calories than carbohydrates because more energy is available in a lipid molecule than a carbohydrate molecule WHY IS THIS THE CASE Energy consumed by various activities kilocalorie consumed gerhouQ Running from Bl 101 class9 9 Dancing after passing BIO 101 510 Bicycling to test the potentialkinetic energy reference 490 Swimming in a sea of knowledge 408 Walking to lab 245 Sitting and absorbing it all 28 Maybe we should try teaching this in a spinning class How cells tap energy Energy is contained in the arrangement of electrons in the chemical bonds that hold an organic molecule such as glucose together During cellular respiration electrons are transferred to oxygen why we need 02 as the CarbonHydrogen bonds of the molecule in this case glucose are broken down When these electrons are transferred they lose potential energy which is released as energy Cellular Respiration Cellular respiration occurs in 3 stages Glycolysis Citric Acid Cycle The Electron Transport Chain Oxidative Phosphorylation All of these steps occur in and around the mitochondria in eukaryotic cells and in the plasma membrane and cytoplasm in prokaryotic cells High energy electrons r n Mitochondrion carried by NADH Occurs in PHOSPHORYLATION Electron Transport and Chemiosm osis C to lasm y p Inner mitochondrial membrane C02 Substratelevel Substratelevel Oxidative phosphorylation phosphorylation phosphorylation Copyngm 2009 Pearson magnum m Cellular Respiration G lycolySIs What two words do you see immediately in the word quotglycolysisquot Glycolysis literally means the quotsplitting of sugarquot Glycolysis begins with a molecule of glucose 6 Carbon sugar and ends with 2 molecules of pyruvate a 3Carbon compound Requires the initial input of 2 ATP molecules Glycolysis Glucose 2ATP 9 2 Pyruvate ionized form of pyruvic acid Glycolysis is a multistep pathway which utilizes at least 6 different enzymes in a metabolic pathway that is anaerobic In the later stages of glycolysis 4 ATP molecules are synthesized using the energy given off during the chemical reactions net gain of 2 ATP Glycolysis httphigheredmcgraw hillcomsitesOO72507470stude ntviewOchapter25animation howgycolysisworkshtml Glycolysis The chemical energy stored in the bonds of the glucose molecule is used to form the high energy compounds ATP Glycolysis is universal among organisms simpler organisms yeasts and bacteria can satisfy their metabolic needs with the ATP produced by glycolysis alone Most organisms have far higher energy demands and must undergo additional stages of cellular respiration to release more energy The Citric Acid Cycle aka The Krebs Cyclequot As pyruvate is formed at the end of glycolysis it is transported from the cytoplasm into a mitochondrion The Citric Acid Cycle breaks down pyruvate in the mitochondrial matrix Compared to glycolysis the Citric Acid Cycle pays big energy dividends to the cell producing 2 ATP molecules plus 10 NADH and 2 FADHZ two very high energy molecules The Citric Acid Cycle The energy stored in NADH and FADH2 is released when these molecules 39shuttle their highenergy electrons to the Electron Transport Chain stage 3 The Electron Transport Chain is oxygendriven and produces the largest amount of ATPs in the entire cellular respiration process For every glucose molecule that enters glycolysis there is a total net production of 36 38 ATPs by the end of the Electron Transport Chain The Electron Transport Chain The Citric Acid Cycle and the Electron Transport Chain occur in the mitochondria The many folds of the mitochondrial inner membrane enlarge its surface area providing space for thousands of copies of the Electron D quot in occurring at once pro N ATP molecules What do cigarette smokers and musk ox have in common Brown fat is 1 of 2 types of fat found in mammals Unlike white fat it is brown in color and especially abundant in newborns and arctic animals Its primary function is to generate heat in animals or in newborns who can not yet shiver What does this have to do with cellular respiration Brown phat Brown fat has extremely high numbers of mitochondria One of the steps in the Electron Transport Chain involves the transfer of hydrogen ions H across the mitochondrial inner membrane which stores energy as a proton Hl diet This energy is used to make ll That s brown phat Many H use an alternative route to generate heat rather than producing ATP with the help of a protein thermogenin Brown fat is especially rich in this protein which causes the proton gradient established during cellular respiration to generate heat rather than ATP Some skinny people may naturally have more brown fat than heavier people How now brown fat Brown fat production in humans usually disappears after infancy but can be stimulated by exposure to severe cold So what do smokers and musk ox have in common Smoking nicotine and caffeine stimulate thermogenin production Less ATP more heat Why you gain weight when you quit smoking and why I won t give up my caffeine addiction And you thought biology was boring ww Hmkr cumpHmus73234E7EN0023EE3 Cellular Respiration Review Beginning with 1 molecule of glucose glycolysis and the citric acid cycle produce a net total of 4 ATP NADH and FADH2 are highenergy molecules produced by glycolysis the 39grooming of pyruvate and the citric acid cycle NADH and FADH2 are electron carriers they transfer electrons amp their energy to other molecules releasing energy and producing ATP Electron shuttle cytoplasm across membrane Qua Mitochondrion GLYcOLYSIs OXIDATIVE was 1 7 M V7 PHOSPHORYLATION Glucose 7 l I xPyruvate Electron Transport and Chemio smosis by substratelevel by substratelevel by oxidative phosphorylation phosphorylation phosphorylation Maximum per glucose CupyvlglquDDQ Pearson Educallun lnc Cellular Respiration Review Oxygen is the final electron acceptor in the Electron Transport Chain Without oxygen electrons cannot be removed from the system and their energy cannot be released to produce ATP In animals breathing is the essential process that brings oxygen into the body for delivery to the cells to participate in cellular respiration Fermentation enables cells to produce ATP without oxygen In the absence of oxygen ATP may still be produced via a process called fermentation Fermentation is the process of deriving energy from organic compounds such as carbohydrates in the absence of oxygen Cellular respiration always begins with glycolysis the presence or absence of oxygen will then determine whether cellular respiration or fermentation will follow Fermentation Remember glycolysis results in the formation of 2 3carbon pyruvate molecules from 1 6carbon glucose molecule and 2 ATP molecules are released When oxygen is lacking certain organisms such as yeasts can convert pyruvate into ethyl alcohol and CO2 which removes electrons and allows continuous ATP production Yeasts are able to perform this process because they have the necessary enzyme to convert pyruvate into ethyl alcohol Fermentation CO2 and ethyl alcohol this sounds familiar For thousands of years people have used alcohol fermentation for brewing beer winemaking and baking Yeasts a type of fungi are used in the process the CO2 generated by fermentation causes bread to rise and makes our libations bubbly while the ethyl alcohol well you know Fermentation Normally ethyl alcohol is released to the surroundings or burnt off during baking but in a wine vat the yeast will die when the alcohol content reaches 15 toxic Some organisms such as yeast can alternate between cellular respiration or fermentation depending upon whether oxygen is available or not others may only use fermentation and are poisoned by the presence of oxygen Fermentation continued In muscle cells another type of fermentation takes place When muscle cells contract too quickly eg strenuous exercise they rapidly use up their oxygen supply which slows ATP production Muscle cells however have the ability to produce a small amount of ATP through glycolysis in the absence of oxygen lactic acid fermentation o The muscle cells convert glucose to pyruvate and then an enzyme in the muscle cells converts pyruvate into lactic acid releasing 2 ATP molecules Lactic acid is toxic and must be removed by the liver amp converted back to pyruvate heavy breathing after exercise helps restore oxygen back to the muscle cells How we use food for energy While we frequently focus on glucose as the starting molecule of cellular respiration or fermentation many other organic compounds are utilized by our cells for energy The Far Side Gary Larson How we use food for energy When you eat a bag of peanuts for example you are consuming lipids proteins and carbohydrates All of these compounds are used in the process of glycolysis while fats rich in carbon and hydrogen and thus many energyrich electrons are broken into 2 carbon fragments which enter the citric acid cycle and yield twice as many ATP as a carbohydrate Food such as peanuts I Carbohydrates RV Sugars fG lu oose GB P 391gtRyruvat e GL COEYSITS caayngm a 2009 Pearson amen Inc Food also provides raw materials In addition to producing ATP for energy many food molecules are used directly as raw materials which the cell uses to construct its structures and perform its funcUons For example many proteins are broken down into amino acids by the cell to make its proteins In return cells also use ATP to make biomolecules that are not present in food ATP needed to drive biosynthesis Su rs f Carbolydrate 39 j capyngmezma Penman Educauan Inc How a cell harvests energy The cells of all living organisms have the ability to harvest energy from the breakdown of organic molecules the atoms of the starting materials end up being released CO2 and H20 In contrast the ability to make organic molecules using CO2 and H20 is not universal Animal cells lack this ability but plants can actually produce organic molecules from inorganic ones using the energy of the sun photosynthesis How do cells reproduce Cell division is at the heart of reproduction Multicellular organisms originate from a rapidly dividing fertilized egg cell eggs and sperm are themselves created from a special type of cell division Cell division replaces wornout or damaged cells keeping the total number of cells relatively constant There are two types of cellular division mitosis and meiosis Cell division and reproduction Asexual reproduction involves the creation of geneticallyidentical offspring from a single parent no eggs or sperm are involved Involves replication of 6 chromosomes the structures containing the organism s DNA a Bacteria yeast protists and certain plants and animals Asexual Reproduction Asexual reproduction is a very efficient means of reproduction Faster than sexual reproduction Increases numbers of organisms quickly Ability to reproduce in absence of mate male doesn t need female and vice versa Genetic diversity however is sacrificed Sexual Reproduction The ability for an organism to form gametes or sex cells eggs and sperm results in the formation of similar but not identical offspring In sexual reproduction the resulting offspring are genetically similar but not i r identical to either parent offspring inherits a combination of genes from each parent Cells arise from preexisting cells 0 Cell division allows an embryo to develop into an adult and is the basis of egg and sperm formation It also ensures the continuity of life from one generation to the next In the case of unicellular organisms cell division can reproduce an entire organism Binary fission Prokaryotes Bacteria and Archaea reproduce by a type of cell division called binary fission quotdividing in half These cells possess a single chromosome which is replicated prior to the cell dividing into 2 What about eukaryotic cells A bacteria contains 3000 genes human cells contain 25000 which are grouped into multiple chromosomes located in the nucleus Each chromosome consists of 1 long DNA strand with hundreds or thousands of genes 0 Integrated into this chromosome are proteins which help maintain its structure and control the activity of its genes Chromosomes Human cells have 46 chromosomes Before a eukaryotic cell can divide it must replicate its chromosomes The DNA molecule of each chromosome is copied and new proteins attach as needed A duplicated chromosome rsan Eauuallon inc Copyrighl to 2009 Pea Chromosome duplication Sister Iquot chromatids J j V Chromosome distribution to daughter cells Centromere Cunylighl o 2009 Pearson Educalmm inc The cell cycle 0 The process of cell division is a key component ofthe cell cycle an ordered sequence of events beginning with the birth ofthe cell from a dividing parent and ending with its own division into 2 cells 0 The cell cycle consists of a growing stage called interphase and the actual cell division called the mitotic phase The Cell Cycle Most ofthe cell cycle in spent in interphase During this time the cell performs its various functions within the organism Additionally the cell acquires a rich supply of proteins creates more organelles such as mitochondria and ribosomes and grows during this time Chromosomes are replicated during interphase The Cell Cycle 0 Interphase is divided into 3 stooges er stages The G1 phase cell grows The S phase cell grows chromosomes replicated The G2 phase cell grows G stands for gap first and second gap S stands for quotsynthesisquot DNA INTERPHASE 5 DNA synthesis Couynghl 2009 Pearson Educanon m The Cell Cycle 0 During interphase the cell grows Gl continues to grow while DNA is replicated S and then grows more as it completes preparations for cell division 62 Cell division occurs in the mitotic phase also called the M phase Accounts for only 10 of the total time required for the cell cycle The Cell Cycle 0 Like interphase the mitotic phase is divided into 2 stages Mitosis the nucleus and all its contents including the duplicated chromomes divide and are evenly distributed to the daughter cells Cytokinesis the cytoplasm is divided into 2 Mitosis and cytokinesis produces 2 genetically identical cells each with a single nucleus surrounding cytoplasm and plasma membrane Mitosis Mitosis the division of nuclear material is subdivided into 5 main stages Prophase Prometaphase Metaphase Anaphase Telophase Mitosis During mitosis chromosome movement is dependent on the mitotic spindle a football go Giants Go Jets shaped structure of microtubules that guides the separation of the 2 sets of separating chromosomes During interphase chromosomes are not distinguishable because they exist as loose fibers of chromatin chromatin becomes more tightly packed and visible as mitosis ensues allowing easy tracking of each step of mitosis Prophase The mitotic spindle forms during the first stage prophase The chromatin fibers containing DNA become more tightly coiled and folded forming discrete chromosomes that can be seen with a light microscope 0 Remember there are 2 pairs of chromosomes at this stage as they were replicated during the S phase of interphase Prophase Visible chromosomes nuclear envelope still present Early mitotic spindle present Prometaphase 0 During the second stage of mitosis prometaphase the nuclear envelope breaks away 0 Proteins embedded in the chromatin attach to microtubules ofthe spindle and move the chromosomes towards the center of the cell Prometaphase Dissolution of nuclear envelope chromosomes moved towards the center of the cell Mitotic spindle extend 39pole to 39pole Metaphase and Anaphase 0 During metaphase the mitotic spindle spreads across the entire cell with the chromosomes aligned perpendicularly at its center remember each chromosome has been replicated into 2 prior to mitosis 0 In Anaphase the sister chromatids of each chromosome separate and move away from each other toward opposing poles METAPHASE Spindle c nnnnnnnnnnnnnnnnnnnnnnnnn inc Meta phase plate ANAPHASE Daughter chromosomes During mitosis each chromosome has been replicated consisting of 2 sister chromatids these chromosomes align and separate during metaphase and anaphase respectively Telophase 0 During the fifth and final stage of mitosis called telophase nuclear envelopes form around the 2 copies of separated chromosomes the chromatin fiber uncoils and the mitotic spindle disappears Sort of a reverse prophase Cytokinesis follows this final stage of mitosis pinching the cell into 2 Telophase and Cytokinesis Got all that The eukaryotic cell cycle consists of Interphase 61 S 62 growth amp DNA replication Mitosis Prophase mitotic spindle forms chromatin condenses Prometaphase nuclear envelope dissolves chromosomes attach to spindle Metaphase mitotic spindle spreads pole to pole with chromosomes aligned at center Anaphase each sister chromatid of replicatec chromosome separates Telophase nuclear envelope reforms chromatin uncoils Cytokinesis cell divides into 2 Cell Division 0 The timing of cell division must be regulated in order to grow and develop normally 0 Skin cells and stomach cells are replaced regularly as they are constantly abraded and sloughed off Other cells such as liver cells do not divide unless damaged In this way cell division repairs wounds and heals Cell Division Proteins regulate cell division by stimulating cells to divide in their presence 0 For example injury to the skin causes blood platelets to release a protein which promotes rapid growth of connective tissue cells that help seal the wound Proteins control each cycle of mitosis and each stage does not occur until triggered to do so by these proteins Cell Division Proteins serve as a control system for each stage of the cell cycle Want a job Research on controls over the cell cycle is one ofthe hottest areas in biology today Why 0 Without check points cells will continue to divide unregulated cancer Cancer Cancer is a disease of the cell cycle Cancer cells divide uncontrollably and do not respond normally to the cell cycle control system Cancer begins when a single cell undergoes transformation from a normal cell to a cancer cell Cancer cells may proliferate into a tumor an abnormally growing mass of body cells Cancer 0 Benign tumors remain at the site and can usually be removed easily with surgery Malignant tumors spread into neighboring tissues and other parts ofthe body interrupting organ function as it goes Cancer cells may secrete molecules that cause blood vessels to spread toward the tumor and allow proliferation ofthe cancer cells via the circulatory system metastasis Cancer Radiation damages DNA in cancer cells moreso than it does in normal cells and can be used as a cancer treatment Chemotherapy is used to treat metastatic or widespread tumors involves the use of drugs that disrupt cell division some drugs prevent the mitotic spindle from forming in the first place however side effects are seen in normal rapidly dividing cells Meiosis Meiosis is the process of cell division in which the number of chromosome is cut in half 0 Unlike mitosis which results in a daughter cell containing the exact number of chromosomes as the parent cell Meiosis takes place in reproductive organs and produces gametes sex cells such as eggs sperm and pollen plants Meiosis Homologous pair of chromosomes 0 Human cells have 46 chromosomes made up of 23 pairs of homologous chromosomes 0 Cells with 2 sets of chromosomes are considered diploid Sister chromatids One duplicated chromosome Capyl gm 3 21m Pearsnn Euubalior inc Meiosis The two chromosomes composing a pair are called homologous because they both carry genes controlling the same inherited characteristics One exception are the sex chromosomes X and Y Females have a homologous pair XX while males have 1 X and 1 Y The other 22 chromosomes are called autosomes Meiosis Homologous pair of chromosomes For both sex chromosomes and autosomes we inherit one chromosome of each pair from our mother and the other from our father From Mother From Father Meiosis The 46 chromosomes in the human cell consists of 23 pairs of homologous chromosomes Homologous chromosomes are similar but not identical they may carry different versions ofthe same genetic information 0 For example one chromosome may code for blond hair while the other codes for dark hair or both may contain the same gene ex Blue eyes Meiosis Human cells contain 22 pairs of autosomes and 1 pair of sex chromosomes X andor Y Chromosome 1isthe largest containing 8000 genes Chromosome 21 is the smallest containing only 300 Sex chromosomes genes mp lvwwvsmenuemuseum mg ukembitianSgenes ssp Meiosis Meiosis is a special type of cell division that will produce cells containing half the number of chromosomes Cells containing half the number of chromosomes are sex cells or gametes Gametes contain a single set of chromosomes and are considered haploid half All other cells containing 2 homologous sets of chromosomes is said to be diploid Meiosis For humans the diploid number is 46 Nearly all of our cells are diploid the exceptions are the gametes Sexual reproduction allows a haploid sperm cell to fuse with a haploid egg cell during the process of fertilization producing a zygote The resulting zygote is diploid it has 2 sets of homologous chromosomes 1 from Mom and 1 from Dad Meiosis Meiosis occurs only in reproductive organs 0 During meiosis a mother cell divides and produces 4 genetically distinct daughter cells which contain half the number of chromosomes as the other cell 0 Why 4 This is because meiosis begins with mitosis insert quotUGHquots here Meiosis reduces the chromosome number from diploid to haploid Just as a cell entering mitosis has duplicated its chromosomes so too does a cell entering meiosis resulting in 92 chromatids sites of crossing over During prophase 1so called because it is the first cycle occuring during Meiosis 1 out of 2 the process of crossing over occurs sister chromatids Crossing over Crossing over is the process by which aligned chromatids of homologous chromosomes exchange genetic segments resulting in a genetically new chromatid The driving force of genetic diversity and evolution Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring 63 Crossing over H39 J Iquot 9 II Jr S 1 1w Schmm m illlhh zllt lnuhlc yrmqnu39 mm Cell division 0 In both mitosis and meiosis the chromosomes duplicate only once in the preceding interphase Mitosis replicates cells for growth tissue repair and asexual reproduction and produces daughter cells genetically identical to the parent cell diploid Meiosis produces haploid cells that are genetically distinct from the parent cell Genetic diversity 0 Changes in an organism s DNA create different versions of genes and resulting characteristics Reshuffling ofthese different versions during sexual reproduction produces gene c variation Genetic diversity For a human there are 23 chromosomes and 223 combinations of chromosomes that meiosis can package into gametes 223 equals 8 million possible combinations Each gamete you produce contains 1 of 8 million possible combinations inherited from your father and your mother The random fusion of egg and sperm will produce a zygote with any of 64 trillion 8 mil x 8 mil combinations of chromosomes Crossing over and Recombination During Meiosis 2 Occurs at 1 or more 3 j points along adjacent chromatids Points contact each other DNA is exchanged m WW ccesmeuence avvABGGcmssmv Mmi Homologous chromosomes carry different versions of genes 0 A pair of homologous chromosomes can bear 2 different kinds of genetic information for the same characteristic Brown coat C black eyes E Coatcolor Eyecolor genes genes Brown B39aCk C E C E g Meiosis y c e e C White Pink c e A White coat c pink eyes e Chromosomes of the four gametes Alterations of chromosome number and structure 0 With 64 trillion possible combinations of chromosomes what could possibly go wrong 0 Chromosome number abnormalities do occur and are often fatal 0 An additional copy of chromosome 21 the short one results in Down s syndrome also known as trisomy 21 Alterations of chromosome number and structure Individuals with Down s syndrome exhibit distinctive features flattened nose bridge short stature heart defects and a shortened l espan The additional chromosome usually comes from the mother with a risk of 1 with pregnancy after age 40 VVhy Alterations of chromosome number and structure Maternal age as arrest on Tnsumy 2r Rwsk of Down Syndrome m I ve births la Mamars age A mmmm an Famuy Phystclan Aug 15 2mm Abnormal numbers of sex chromosomes Alteration in the number of copies of sex chromosomes are not lethal TABLE 822 ABNORMALITIES OF SEX CHROMOSOME NUMBER IN HUMANS Sex Origin of Frequency Chromosomes Syndrome Nondisjunction in Population XXY Klinefelter syndrome Meiosis in egg or 1 male sperm formation 2000 XYY None normal male Meiosis in sperm 1 formation 2000 XXX None normal female Meiosis in egg or sperm formation 1000 XO Turner syndrome Meiosis in egg or 1 female sperm formation 5000 capyngm to 2009 nnnnn an Ed lllllllll nc Abnormal numbers of sex chromosomes 0 The Y chromosome is very small and carries relatively few genes What about the X chromosome It s big and it does carry a lot of genes 0 In females the extra X chromosome is inactivated since the presence ofthis additional chromosome would otherwise be fatal Abnormal numbers of sex chromosomes The inactivation ofX chromosomes is random results in a random expression of genes Alterations Of Chromosome structure can cause birth defects Other errors can occur involving deletion or duplication of chromosome structure Such chromosomal changes present in sperm and egg can cause congenital disorders Such changes in a somatic cell may contribute to cancer not inheritable why damage to our DNA may cause cancer radiation UV etc The Chemical Basis of Life Why are we studying chemistry in a biology course a At the base of the hierarchy of life are atoms and molecules Many biological processes take place on a molecular level The food we eat is made up of chemical elements many of Wthh are essential to life 3 3922s H ftp1lww de ny s39beerbarre pu Elements Atoms and Molecules 0 Living organisms are made up of 25 chemical elements 0 An element is a substance that cannot be broken down to any other substance by ordinary chemical means Remember your Periodic Table of Elements Oxygen 0 Carbon C Nitrogen N Hydrogen H 96 of the weight of the human body Main ingredients of proteins sugars and fats Elements Atoms and Molecules The remaining 4 is made up of Calcium Ca 9 bone formation Phosphorus P 9 DNA synthesis Potassium K 9 cell signaling nervous system Sulfur S Sodium Na Chlorine Na Magnesium Mg mostly Elements Atoms and Molecules What about the remaining 001 Trace elements are present in trace or minute quantities but are extremely important 0 Examples oftrace elements include Iron Fe hemoglobin binds oxygen Copper Cu enzymes electron transport Fluorine F prevents tooth decay added to municipal water Iodine I thyroid enzymes deficiency 9 goiter quotiodized salt TABLE 21 ELEMENTS IN THE HUMAN BODY Percentage of Element Symbol Human Body Weight Oxygen O 650 Carbon C 185 Hydrogen H 956 963 Nitrogen N 33 Calcium Ca 15 Phosphorus P 10 Potassium K 04 Sulfur S 03 Sodium Na 02 Chlorine CI 02 Magnesium Mg 01 Trace elements less than 001 boron B chromium Cr cobalt Co copper Cu fluorine F iodine I iron Fe manganese Mn molybdenum Mo selenium Se silicon Si tin Sn vanadium V and zinc Zn Conyrighl 2009 Pearson Education inc Elements Atoms and Molecules 0 Not all elements are good for us Mercury toxic to humans 9 mercury poisining Mercury is concentrated in fish especially of higher trophic level eg swordfish tuna shark accumulates and remains in body Leads to tremors impaired cognitive thinking skills sleep disturbance The human body rids mercury via nails and hair The quotMad Hatter Elements Atoms and Molecules An element can combine to form compounds A compound is a substance consisting of 2 or more different elements Much more common than elements Sodium chloride NaCl quottable salt 1 part sodium and 1 part chlorine Water H20 2 Hydrogen atoms and 1 Oxygen atom Proteins are compounds CHON S different arrangement and s of atoms 9 different proteins Elements Atoms and Molecules 0 An atom is the smallest unit of matter that still retains the properties of an element 0 An atom is made up of Proton charge Electron charge Neutron neutral no charge 0 Elements differ by the number of protons neutrons and electrons For example Helium He has 2 p e amp n Carbon C has 6 p e amp n Electron CIOUd Atomic number the number Gequot of protons each element has Its own unique number of Example Protons In this case Carbon s atomic Carbon Atom numberis 6 6p Nucleus 6 P t r0 ons Mass number the sum of protons and neutrons 6 o Neutrons in the nucleus In this case Carbon s mass 6 e Electrons number is 12 6p 6n unwrigm 2009 Pearson Education Inc Isotopes 0 All atoms of an element have the same atomic number number of protons but some atoms of an element may differ in mass number number of protons number of neutrons different isotopes of an element 0 Different isotopes of an element have the same number of protons and electrons and so behave identically chemically but have different numbers of neutrons Isotopes 0 Example Carbon isotopes Carbon 12 mass number of 12 6p 6n Carbon 13 mass number of 13 6p 7n Carbon 14 mass number of 14 6p 8n Remember atomic number of Carbon is 6 so all isotopes of Carbon must have 6 protons it s the neutron number that differs Carbon 12 stable accounts for 99 of all Carbon Carbon 13 stable accounts for N1 of all Carbon Carbon 14 radioactive found in minute quantities Isotopes Stable isotopes do not decay they tend to maintain their neutrons Radioactive isotopes do decay the nucleus decays spontaneously releasing particles and energy gamma rays andor subatomic particles Radioactive isotopes quotradioisotopesquot exist naturally but may also be created artificially Radioisotopes 0 Radiation from decaying isotopes can be hazardous to your health Causes cellular damage damages cellular molecules The particles and energy thrown off by radioactive isotopes break chemical bonds and can also cause abnormal bonds to form 9 cancer DNA damage Uranium from rocks naturally decays into Radon a radioactive gas basements can have high levels 9 lung cancer Radioisotopes Radioactive isotopes can also be helpful Biologists use radioactive tracers to follow molecules as they undergo changes in an organism A positron emitting tomography quotPETquot detects and tracks locations of radioactive materials in the body Radioisotopes can also help us age fossilized organisms 14C Elements Atoms and Molecules The electron arrangement determines the chemical properties of an atom Electrons are arranged in shells or energy levels called energy shells The number of electrons in the outermost shell determines the chemical properties of the atom The first 18 elements in the Periodic Table Hydrogen Helium 39 l Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon 7 A 7 c n re 4quot 1quot u Yr H I h il i In x n a l M ii i i l i l 1 1 K f 439 lt Sodium Magnesium Aluminum Silicon Sulfur Chlorine Argon r n u amp H 39x 77 x t I y x r r w i a til i I 3 lit in wt 1 it at 3 39 41 g x tquot k 4 quot9 g 2009 Atoms whose shells are incomplete tend to interact with other atoms to gain lose or share electrons Ionic bonds When atoms gain or lose electrons they also gain or lose electrical charge A charged atom is a called an ion The electrical charges between two ions results in an ionic bond the electrical attraction of each ion holds them together The resulting compound is electrically neutral Formation of an ionic bond Transfer of u electron I CI Na Sodium atom Chlorine atom Sodium ion Chloride ion Sodium chloride NaCl Copyrighl zone Pearson Emma on in Covalent bonds Two atoms may also share one or more pairs of outer shell electrons When atoms share outer shell electrons they form covalent bonds Atoms formed by ionic or covalent bonds form a molecule These bonds are very strong A molecule can consist of 2 different elements or 2 atoms of the same Molecules Molecules can be represented in multiple ways Molecular formula Electron configuration Structural formula ALIERNATIVE wAvs w REFRESENY MOLECULES Molecular suucmml Formula EIamn conligumian Formula H2 H 7 H Slvgle bow o 070 Double bond H l are H C H Methane l H H20 07H Wmev Polarity Unequal electron sharing creates polar molecules especially in polar bears just kidding still awake Atoms in a covalently bonded molecule are in a constant tug o war for their shared electrons 0 An atom with high electronegativity its attraction for shared electrons can pull electrons towards its nucleus and away from the other sharing atom Polarity 0 A polar molecule results from the unequal distribution of electrical charges polar covalent bond A water molecule is a polar molecule H The oxygen atom in water is highly electronegative it attracts the shared electrons much moreso than does the Hydrogen atoms so the shared electrons spend more time near the Oxygen than the Hydrogen atoms Water is a polar molecule The bonds that exist between 2 polar molecules are called hydrogen bonds very weak compared to ionic and covalent Hydrogen bonds Speaking of water Water is the molecule of life Hydrogen bonds make water cohesive its molecules tend to stick together This cohesion allows plants to transport water and nutrients from their roots to their leaves think of a giant redwood Water has an extremely high surface tension the measure ofthe difficulty to stretch or break the surface of a liquid A water strider walks on water and let s not forget Jesus Christ Superstar er Lizard httpwwwyoutubecomwatchv45yabrnrkaampfeaturerelated Water is essential to life Water s hydrogen bonds moderate temperature Water is able to absorb a great deal of heat energy without an increase in temperature because of its hydrogen bonds Heat must be absorbed to break hydrogen bonds and heat is released when hydrogen bonds form To increase temperature of water heat energy must first disrupt the hydrogen bonds when water is cooled more hydrogen bonds form Water s hydrogen bonds moderate temperature Because a water molecule takes a lot of energy when it evaporates this can lead to evaporative cooling 0 Whenever a person sweats the evaporation of water removes heat energy from the body reducing the body s temperature Why dogs pant and elephants waddle in mud An elephant s skin has evolved to trap mud WWW su amawgaturnetan gdum ma sE Eghants mm Water is the solvent of life Because of water s polar properties and hence its hydrogen bonds water is an incredible solvent A solvent is the dissolving agent of a solution a liquid consisting of uniform mixture of 2 or more substances The substance that is being dissolved is called a solute think quotuquot goes into solution Water is the solvent of life Solutes whose charges or polarity allow them to adhere to water molecules will dissolve in water 9 an aqueous solution 0 Try this at home Fill a cup of water or a graduated cylinder if you have one although I d be surprised to the very top and then add small amounts of salt NaCl continuously The cup will NOT overflow until it becomes completely saturated requiring lots of salt Ion in Salt solution crystal nnnnnnnnnn ems Fearmn Eumnan m Water s amazing properties Water exists in all phases gas liquid solid on Earth Jeopardy question What is the molecular formula of ice Because of hydrogen bonds ice is less dense than water This prevents lakes ponds and even the ocean from freezing solid fish dolphins walruses very grateful Hydrogen bond Ice Liquid water Hydrogen bonds Hydrogen bonds are stable constantly break and reform Thank you Hydrogen Bonds 39 an Molecular Biology Molecular biology is the study of DNA Its structure How it replicates and assembles to create geneticallydistinct offspring How it controls the cell by directing RNA and protein synthesis How does DNA store genetic information copy it and pass it along from one generation to the next DNA and RNA DNA and RNA are nucleic acids consisting of long chains of nucleotides collectively called a polynucleotide There are 4 types of nucleotides that make up DNA each with a different nitrogenous base Adenine A Cytosine C Thymine T Guanine G Sugarphosphate backbone 1 H Phosphate groupg itrogenous bas Sugar c c H N 0 o l hymine T 2 w I C H C Nt l H c H I O H Su ar 639 9 deoxyribose A polynucleoti 439 Nitrogenous base A G C or T DNA nucleotidK Phosphate CH 39 ngup H3ccc DN DNA nucleotide cagyngm 2mg Fearsun Enucamn me DNA and RNA RNA has the nitrogenous base Uracil U instead of Thymine T and is usually singlestranded DNA is doublestranded and forms a double helix The 2 sugarphosphate backbones that form the double helix run in opposite directions 5 to 3 and 3 to 5 Each strand of DNA runs in opposite directions Hydrogrgn bond L0H Base tach 30 3H2 pair 9 61 quota 1310 E Hzc o 339 g 70 132 1 go Hsc 0 22 3 OH 2 0 Ribbon odel Partial chemicalstructure cagyngmo 2009 Pearson E h uo Computer model DNA replication depends on specific base pairing The specific pairing of bases in DNA is evidence for a copying mechanism for the genetic material Knowledge of the sequence of bases in 1 strand of DNA allows you to determine the sequence in the second strand When 2 strands of DNA separate each strand serves as a template for the assembly of a complimentary strand onpyngm zany Pearson Educanun Inc DNA Replication The human genome all genes collectively contains over 6 billion base pairs in 46 chromosomes 23 39homologou s pairs Yet DNA replication requires only a few hours and is astonishingly accurate How does this process occur and what controls it DNA Replication DNA replication requires more than a dozen enzymes and other proteins of course Replication of DNA begins at specific sites called origins of replication Origins of replication consist of a specific sequence of nucleotides where proteins attach to the DNA and separate the strands Replication then proceeds in both directions Origin of replication Two daughter DNA molecules DNA Replication Eukaryotic DNA has many origins of replication shortening the overall time needed for the replication process Replication occurs in bubbles of parental old and daughter new DNA Eventually all the bubbles merge yielding 2 completed daughter strands of DNA Daughter strands grey Parental strands blue DNA Replication The enzymes that link DNA nucleotides to a growing daughter strand are called DNA polymerases Remember that DNA s sugarphosphate backbones run in opposite directions DNA polymerases add nucleotides only to the 3 end never to the 5 end Thus a daughter strand grows from 5 to 3 Say what DNA polymerase molecule aughter strand 5 Parental DNA 1 synthesized 3 continuously s V augld39lter 3 zyri39ftrhesized in pieces Since the 2 DNA strands run in opposite directions and replication always begins at the 3 end the new daughter strand will be laid down beginning at its 5 end 1 daughter strand is synthesized continuously while the other must work outward from the forking point If Formed Formed 39 n Formed last DNAligase Qveralldirection ofreplication The new strand is synthesized in short pieces as the DNA strand opens up Another enzyme called DNA ligase then links the pieces together to form a single DNA strand Thank you polymerases DNA polymerases also carry out a proofreading step to quickly remove any nucleotides that have been paired incorrectly during replication DNA polymerases and ligases are also involved in repairing DNA damaged by harmful radiation or toxic chemicals including those found in cigarette smoke DNA Replication DNA replication ensures that all cells in a multicellular organism carry the same genetic information DNA replication occurs during interphase The DNA genotype is expressed as proteins which provides the molecular basis for phenotypic traits DNA dictates the synthesis of proteins which determine the traits physically expressed by an organism DNA is transcribed into RNA and translated into Protein A gene does not build a protein directly Instead a gene dispatches its instructions for building proteins in the form of RNA which in turn directs protein synthesis The transcription of DNA into RNA and the subsequent translation of RNA into proteins is considered the quotcentral dogmaquot of molecular biology Nucleus quot Cytoplasm Transla ion of RNA into Prt 8 r I V J 5335 k Protein Coaynghl 2009 Pearson Educamn me DNA is transcribed into RNA and translated into Protein ln eukaryotic organisms DNA is stored in the nucleus where it is transcribed into RNA a process called transcription RNA translates the information from DNA into proteins in the cytoplasm or to be more precise in the ribosomes we ll come back to this a process called translation Genetic information written in codons is translated into amino acid sequences A typical gene conSIsts of hundreds or thousands of nucleotides in a specific sequence The sequence and number of these nucleotides determines the protein produced by this gene and hence its resulting phenotype DNA must first be rewritten transcribed as a sequence of RNA Genetic information written in codons is translated into amino acid sequences Translation then converts the nucleic acid language into the polypeptide protein language The sequence of RNA nucleotides dictates the sequence of amino acids of the polypeptide being produced Thus the RNA molecule acts as a messanger carrying genetic information from DNA DNA strand Transcription v NA Translation Jr Polypeptide N Amino acid Copyrighl 2m Pesrsun Enucallan me Genetic information written in codons is translated into amino acid sequences In order for translation to proceed the sequence of the 4 nucleotides in RNA AU CG must somehow specify the 20 amino acids used to make up proteins The flow of information from gene to protein is based on a triplet code genetic instructions for the amino acid sequences of a polypeptide chain are written in DNA and RNA as a series of 3base 39words called codons The Genetic Code The genetic code is a set of instructions indicating which codons are translated into which amino acid The genetic code does not only specify which codons code for which amino acids but also specify start and stop signals which begin and end protein synthesis respectively For each of the 20 amino acids there are 24 codons which code exclusively for them Second base u c A G uuu ucu39 UAU UGU U Phe Tyr Cys U uuc ucc me we c 1 39 quotv A G u c C Leu Pro Arg 3 CUA CCA CAA Gm CGA A g B E CUG CCG CAG CGG G n 39 392 g Auu39 Acu39 AAU AGu u E u Asn Ser 39 c G u Asp Guc Gcc me me c G Val Ala Gly GUA GCA GAA Glu GGA A GUG GCG GAG GGG G canwgm n 2009 Pearson Edwahmn me The Genetic Code The genetic code is nearly universal humans cells can translate bacterial RILIA IE a Emal mmmml Start Stop codon codon Translation Polypeptide Lys a RNA Transcription An enzyme called RNA polymerase attaches to an area of one of the DNA molecules in the double helix and moves along the DNA strand 39reading the nucleotides It then selects complimentary nucleotides and links them one by one via hydrogen bonds A nucleotide sequence called a promoter serves as a start signal while a terminator sequence marks the end of transcription RNA polymerase M26 DNA of gene r Promoter Terminator DNA DNA 0 Initiation Mtcv Wm Area shown Elongation in Figure 109A 9 Termination 301 I Wrm Completed rr RNA 1 i L t r it 1 lt polymerase capyngm a my Pearson Education Inc RNA nucleotides RNA polymerase Direction of transcription Template strand of DNA Newly made RNA Messenger RNA The type of RNA that encodes amino acid sequences is called messenger RNA mRNA In eukaryotic cells mRNA leaves the nucleus where it had been transcribed and enters the cytoplasm Before mRNA can leave the nucleus it is modified A 39tail39 and 39cap39 are added lntrons are removed A cap and tail are added to protect the mRNA strand facilitate its transport out of the nucleus and to help ribosomes bind to it Exon Exon Intron Intron Exon Cap RNA with cap and tail 1 Transcription l 1 Addition of cap and tail transcript Introns removed Tail mRNA Copyrighl K 2009 Pearson Edunalion m E l Exons spliced together Coding sequence Nucleus 4 4 r Ar 1 cytoplasm Introns are intervening sequences of DNA which do not code for amino acids must be removed Exons are the coding regions parts of the gene which remain and are translated into amino acids Transfer RNA In order to convert the 3letter codons of nucleic acids into a single amino acid a cell must employ a molecular interpreter transfer RNA tRNA tRNA recognizes the codons in the mRNA molecule and picks out the appropriate amino acids for incorporation into the growing polypeptide Transfer RNA tRNA recognizes codons from mRNA via a special triplet of bases called an anticodon which is complimentary to the codon on the mRNA When the codon of mRNA complements the anticodon of tRNA the appropriate amino acid is laid down at the other end of the tRNA molecule Amino acid attachment site Hydrogen bond RNA polynucleotide chain Canyngm 2009 Feavsnn Eduuanan Inc Transfer RNA For each amino acid there is a specific type of tRNA that it will bind to And for each tRNA there is a specific enzyme which binds the amino acid to its specific tRNA molecule How many enzymes or tRNA molecules for that matter are there Translation mRNA leaving the nucleus enters the cytoplasm where it binds to a ribosome Remember all cells contain ribosomes Translation begins when the mRNA molecule arrives at the ribosome While mRNA was being synthesized tRNA molecules were already uniting with their specific amino acids Translation The tRNA molecules then begin transporting their amino acids to the ribosomes to meet the mRNA molecule Ribosomes are made up of proteins and a type of RNA called ribosomal RNA rRNA The ribosomes contain binding sites for both mRNA and tRNA tRNAbinding sites Large subun mRNA Mndhg she SmaH subun Copyrigmem Paarsun Ed an In Next amino acid to be added to polypeptide Growing polypeptide mRNA 1 J 74 39 odon of tRNA aapyngme 2099 Pearson Educaliun Inc New peptide bond forming oElongation A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome one codon at a time 4 1 9 Poypeptide Termination The ribosome recognizes a stop codon The polypeptide is terminated and released oagyngm a 2003 Pearson Edunallom lnc Translation Translation begins with a start codon and ends with a stop codon The amino acid methionine Met is always translated by the start codon AUG What would the anticodon look like Stop codons UAA UAG and UGA do not code for amino acids but instead act only as signals to end translation Review Describe the differences between mRNA tRNA and rRNA What bases are found in DNA In RNA Which molecule has codons Anticodons What is transcription Translation Which happens first and where does each occur in the cell Mutations A single change in the amino acid coded for by a gene can lead to mutation and a single change to a single nucleotide can lead to a change in amino acid Mutations can be caused by a nucleotide addition deletion or substitution Insertions or deletions are the most disastrous l ll wwwmilehivecomxmenoriginswolver inejpg Mutations The production of mutations can occur spontaneously during DNA replication or by a mutagen a physical or chemical agent such as X rays and ultraviolet light physical What would happen if a mutation occurred in an intron An exon 7 Viruses A virus is a fragment of nucleic acid surrounded by a protein coat Viruses are infectious they are parasites that can reproduce only inside living cells The host cell provides most of the components necessary for replicating transcribing and translating the viral DNA You can run but you can t hide Viruses infect bacteria archaea Viral DNA protists plants and animals and are found in nearly every ecosystem on Earth Viruses contain genes made of DNA or RNA The protein coat or membrane in some cases allows the virus to penetrate the host cell Viruses Viruses cause illness because they attach to a cell and inject their DNA into it o The host cell is then instructed by the viral DNA to produce more copies of itself and to translate proteins which together serve to assemble more viruses Eventually the cell lyses and releases an army of viruses Lytic cycle of viruses g g A Phage attaches Phage injects DNA Phage DNA directs host to bacterial cell cell to make more phage 3 DNA and protein parts New phages assemble Cell lyses and s s releases new phages Davyrlghl e7 2999 Pearson Euucamn lnc Viruses The common cold is caused by viruses containing RNA as are measles mumps AIDS and polio DNA viruses cause hepatitis chicken pox and herpes Glycoproteins on the virus s outer coat enable it to attach to receptor proteins on the host cell s plasma membrane very specific Got NyQuil The amount of harm caused by viruses depends largely on how quickly an organism s immune system responds to fight the infection and also on the ability of the infected tissue to repair itself Our respiratory tract can efficiently replace damaged cells by mitosis and we usually recover quickly from colds but damage done to nerve cells by the Poliovirus is permenant How do viruses spread Ever wonder why we sneeze and cough whe 39 39 quot U0T025EltRETS0M Cold sores herpes chicken pox Viral DNA may become part of the host chromosome Viruses reproduce via the host cell as previously described in the lytic cycle But viruses can also reproduce via an alternative route called the lysogenic cycle During a lysogenic cycle viral DNA is replicated without destruction of the host cell In this case viral DNA is incorporated into the host cell s DNA and is replicated every time the host cell prepares to divide Lytic and Lysogenic viral Cel l ses IIIGa Phag es assem ble Copyllgm 2009 Pearson Education m l y g i releasing phages I Phage injects DNA r 7 cles Phage Attaches to cell Bacterlal Phage DNA chromosome Pquot 7 Many cell L divisions Lytic cycle Lysogenic cycle Lysogenic bacterium reproduces Phage pNA Prophage normally replicating the cIrcularIzes prophage at each cell division Phage DNA inserts into the bacterial chromosome by recombination New phage DNA and proteins are synthesized Viruses The bacteria that cause diphtheria botulism and scarlet fever would be harmless were it not for the viral DNA encoded into their DNA Mutations of existing viruses are a constant source of new emerging viruses RNA viruses are usually the culprit errors in replication are not subject to the types of proofreading mechanisms that help reduce mutations in DNA replication Question of the day or century millennium etc Are viruses alive Do they reproduce Do they grow and develop Do they take in energy and process it to perform their activities Do they respond to their environment Do they adapt Want to learn more ff m ogv Department The Biol res The curse of in uenzavims on human socien es howlo deal with szasonal Epidzmicsand with I12 cunznl nzw mm pandemi 39 A M Swme Flu H1Nl w Ezkavdwxmmar PH D ugummmmmwsgngmm Mxtrnhm ngv Ramang a 9mm mm m nfemws steases 5mm anemnne 5man mm Wed Dec 9th 11001215pm The Montzuk Paint Room Babylon Student Center Organic compounds Nearly all the molecules a cell makes are Carbon based organic compounds Carbon is unparalleled in its ability to form large diverse molecules The outer electron shell of Carbon has 4 electrons Carbon completes its outer shell by sharing electrons with other atoms Carbon and other elements in 4 covalent bonds Organic Compounds By sharing its electrons Carbon can bond to four other atoms By doing so it can branch in up to four directions enabling the formation of diverse compounds Methane CH4 is one of the http cre at oooooooooo orgl iiiii esb yrsa2 5 simplest organic compounds 1 Carbon atom shares its H C electrons with 4 Hydrogen atoms Organic Compunds When Carbon shares electrons with Hydrogen atoms a hydrocarbon results Hydrocarbons are the major components of petroleum Petroleum crude oil consists of the partially decomposed remains or organisms that lived millions of years ago This is why the burning of fossil fuels increases carbon dioxide into our atmosphere CH4 2 O2 9 2 H20 CO2 Energy Organic compounds The unique properties of an organic compound depend on the size and shape of its Carbon skeleton the chain of Carbon atoms can be branched or unbranched and on the groups of atoms that are attached to that skeleton i 1 i v H httpenwikipediaorgwikiCarbonskeetonCarbonskeleton D H OH I ITJ I T T T T T T T quotaquot H H H H H Ethane Propane Length Carbon skeletons vary in length T H C H T T T T T T T T T T T T T H H H H H H H Butane Isobutane Branching Skeletons may be unbranched or branched w T T 39r r 39r w 39v H CC l H H f CC f H H H H H lButene 2Butene Double bonds Skeletons may have double bonds which can vary in location T H gt H H c H C C c C Hl PT T A c c H C H H c H I H H H Cyclohexane Benzene Rings Skeletons may be arranged in rings capyngmo 2009 Pearson Edunanon m Organic Compounds There are 6 chemical groups that are important in the chemistry of life These groups known as functional groups affect the molecules function by participating in chemical reactions in characteristic ways characteristic to functional group or by influencing the molecule s shape 5 functional groups are polar their Oxygen or Nitrogen atoms exert a strong pull on shared electrons makes them hydrophilic water loving and water soluable Functional Group FUNCTIONAL GROUPS OF ORGANIC COMPOUNDS Hydroxyl group OH Carbonyl group C70 Carboxyl group COOH Amino group H2 Phosphate group iopogz Methyl group 7 H3 cminqu o 2009 Pealso Examples l I H C C OH H H Alcohol H H o H I I 0 I II I H7C7C7C HiCiciCiH I I H I I H H H H Aldehyde Ketone H o o H C Clt c I OH 0 Carboxylic acid Ionized H H H CI N N H I H H H Amine Ionized O 0 0 I I Adenosine O O P O 0 p II o p II II o 0 Organic phosphate ATP H N I NH CCH II O CNCH H Methylated omponnd Hydroxyl group polar consists of a Hydrogen bonded to an Oxygen Carbonyl group polar Carbon linked by a double bond to an Oxygen Carboxyl group polar a Carbon doublebonded to both an Oxygen and a Hydroxyl group Amino group polar composed of a Nitrogen bonded to 2 Hydrogen atoms and the Carbon skeleton Phosphate group polar consists of a Phosphorus atom bonded to 4 Oxygen atoms Methyl group nonpolar and not reactiveCarbon bonded to 3 Hydrogen Organic Compounds 0 Isn t organic chemistry fun How about a working example Male and female sex hormones differ ONLY by functional group 0 This change in functional group may seem subtle but results in different actions ofthese molecules which help produce the physical features characteristics of males and females Same structure but different functional groups Estradiol female sex hormone HQ 7 Methyl roup Hydroxyl group Carbonyl grou Testosterone male sex hormone Male 0 Canyrlgm 2009 Pearson Edunallon lnc Organic Chemistry is great In addition to water all other biological molecules are organic carbon based molecules 0 There are many organic molecules but four of them are extremely important Carbohydrates Lipids Proteins Nucleic Acids Polymers Cells make most of their large molecules by joining smaller molecules into chains called polymers 0 A polymer is a macromolecule because of its great size Polymers consist of many identical or similar building blocks monomers strung together much like a long train consists of many individual cars Polymers The variety of polymers made by a cell is potentially endless The arrangement and number of monomers can lead to countless different polymers Carbohydrates lipids proteins and nucleic acids are polymers sort of they sometimes act like polymers Polymers The key to the great diversity of proteins and DNA is arrangement the variation in the sequence in which monomers are strung together 0 DNA is built of only four monomers nucleotides and proteins are built from only 20 kinds of amino acids both of which are incredibly diverse the proteins in you and a fungus are made with the same 20 amino acids Polymers 0 A cell links monomers together to form polymers by a dehydration reaction a reaction that removes a molecule of water An unlinked monomer has a hydroxyl group OH at one end and a hydrogen atom H at the other end For each monomer added to the chain a water molecule is removed Dehydration Reaction jquot W0 g l l polymer monomer Hydrogen Hydroxyl atom group By remwgyjmgggjgpe hydroxyl group of the polymer and the hydrogen atom of the monomer that s being added a water molecule is released Dehydration Reaction e Dy m 5 am Psavson Euucanun Inc Hydrolysis Just as removing a water molecule builds a polymer the addition of a water molecule breaks a polymer chain Cells frequently must break down polymers because they are otherwise too large to enter the cell Hydrolysis Enzymes Both dehydration reactions and hydrolysis require the help of enzymes to make and break bonds 0 Enzymes are specialized macromolecules that speed up the chemical reactions in cells 0 Enzymes are extremely important without them many reactions cannot take place If you lack lactase you cannot hydrolyze the bond in lactose Carbohydrates mm mmhaescummemsmes Wuvdpvess cum2mm ZSpaghemmeamaHsjpg Carbohydrates Carbohydrates are a class of macromolecules that includes sugars starches and fiber Just as their name implies they are made up of carbon quotcarboquot hydrogen and oxygen quothyd rate Carbohydrates constitute a major source of energy in our diet unless you re on Atkins Carbohydrates are produced by plants during photosynthesis Carbohydrates Carbohydrate s monomers are monosaccharides Monosaccharides are small sugar monomers includes simple sugars such as fructose and glucose These monosaccharides can be be linked together to form polysaccharides Polysaccharides contain many monosaccharides disaccharides contain 2 monosaccharides Carbohydrates Monosaccharides are the fuel for cellular work Monosaccharides generally have the molecular formula that are some multiple of CHZO for example the formula for glucose is C6H1206 Monosaccharides are classified by the number of carbons in their carbon chain 5 carbon and 6 carbon monosaccharides are most important for life Carbohydrates Glucose is water soluble and is transported by body fluids to all cells where it is metabolized to release energy Glucose is the starting material for cellular respiration we ll come back to this Glucose is the main product of photosynthesis we ll come back to this too Carbohydrates Important disaccharides are created when glucose links with other monosaccharides Maltose a disaccharide composed of 2 glucose units Sucrose table sugar a disaccharide composed of glucose and fructose Lactose milk sugar a disaccharide composed of glucose and galactose Carbohydrates 0 When glucose and fructose molecules combine to form sucrose a water molecule is produced dehydration reaction When the sucrose disaccharide is split water must be added in a hydrolysis reaction 0 Remember lysis means quotto split so hydrolysis will break a polymer chain in this case a disaccharide into a monosaccharide Carbohydrates Polysaccharides are polymers of monosaccharides large molecules made up of hundreds are thousands of monosaccharides linked by dehydration reactions Polysaccharides function as storage molecules or as structural compounds 0 The most common types are polysaccharides are starch glycogen and cellulose Polysaccha rides Starch a storage polysaccharide consists entirely of glucose monomers produced by plants during photosynthesis a major food source for humans n a 7 e 7 x i 39 1 r 39 i 2 r i I I 39 r i u I tuba n n x 39 1 v n A 39n quot i quot 4 i 3 I in w r drywontonmee flickrcom Copyright 2007 David Monniaux httnlWVM of Wheat Polysaccha rides Glycogen a storage polysaccharide stored and made in liver and muscle cells and broken down when needed 0 After a meal containing carbohydrates is eaten and digested the pancreas secretes insulin to convert the ingested glucose into glycogen When blood glucose levels drop and energy is needed glucagon is released to breakdown glycogen into glucose molecules for energy eunyngmeme mamaquot mmumiei in pmissm required mamarmquot ur nvlny Eating carbohydrate 39 eal increasing blood glucose Pancreatic Islets f Insulin secretion i Glucagon secretion Formation o glycogen in liver and fat in adipose tissue Metabolism Fasting or exercise Decreasing blood glucose Pancreatic Islets Insulin secretion Glucagon secretion Breakdown of glycogen in liver and fat in adipose tissue Polysaccha rides Diabetes is a disease in which glycogen metabolism is abnormal Caused by low levels of insulin or a failed response to insulin Type 1 Diabetes juvenile Little or no insulin productionmutation no insulin made or non functional glucose excreted in urine Type 2 Diabetes adult onset Normal or elevated levels of insulin but cells no longer respond to the insulin Polysaccha rides Cellulose structural polysaccharide Cellulose is the most abundant organic compound on Earth forms plant cell walls Most animals including humans do not have enzymes that can hydrolyze the glucose links in cellulose Humans use cellulose as fiber pushes food through digestive tract absorbs water and eases defecation Polysaccha rides Cellulose is however used by many animals as a source of nourishment Ruminants cows sheep goats deer antelopes bison giraffes first soften this plant based food in their rumen or first stomach and regurgitated and re chewed quotchewing their cud yum The mass is re ingested and broken down by microbes that are able to break down the cellulose Polysaccha rides Another important polysaccharide is chitin Chitin is also a structural polysaccharide forms the exoskeleton of insects spiders and crustaceans Also provides support for the cell walls of many fungi WWW flickr com photosSklender 1018449663 Lipids 0 Unlike carbohydrates which are water soluble hydrophyllic lipids are hydrophobic quotwater fearing Lipids are diverse compounds grouped together because they do NOT mix with water Lipids include oils fats waxes phospholipids and steroids Contain only Carbon Hydrogen and Nitrogen linked by nonpolar bonds Lipids Lipids are important for energy storage 0 The animal body usually contains only about 1 day s supply of glycogen Lipids on the other hand can be stored much longer and contain twice as much energy as a polysaccharide