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Bisc 205 exam 1 study guide Atomic mass top number of protons of neutrons Atomic number lower number of protons Ionic bondingIons formed when electrons are transferredfrom one atom to another Covalent bondingatoms share electrons so each atom ful lls octet Nonpolar covalent sharing of electrons between two atoms is fairly equal Polar covalent sharing of electrons between atoms h20 is unequal Electronegativity attraction of an atom for electrons in a covalent bond Hydrogen bonding attraction between partially negative and partially positive molecules polarity in h20 molecule causes the hydrogen atoms in one molecule to be attracted to the O atoms in other water molecules Dipoles sight negative or sight positive charges Water is a polar molecule Properties of water High heat capacity high heat vaporization converting 1g of hottest water to a gas requires input of 540 calories of heat energy Water is a solvent Hydrophilic interacts with water Hydrophobic do not interact with water water cannot dissolve these molecules H20 molecules can be both cohesive and adhesive h20 molecules cling together because of hydrogen bonding cohesion h20 positive and negative poles allow it to adhere to polar surfaces adhesion h20 is an excellent transport system both outside and within the organisms Water has high surface tension the stronger the force between molecules in a liquid the greater the surface tension allows some insects to walk on surface of pond Frozen water is less dense than liquid water as liquid water cools molecules comes closer together when water forms ice it expands forming a crystal lattice Acids high H concentration they are substances that release hydrogen ions when dissociated in h20 Basic low H concentration substances that dissociate in water and release OH ions that bind H or substances that do not dissociate but can themselves PH Scale Ph below 7 is acidic Ph above 7 is alkaline or basic Ph of 7 is neutral Buffer is a chemical or combination of chemicals that keeps Ph within normal limits Organic moleculesl always include C amp H Those with only c and h are hydrocarbons Functi0nal groups are speci c combination of bonded atoms that always react in the same way when present in another molecule Hydrocarbons are very nonpolar Macromoleculesl contain many molecules joined together Monomers simple organic molecules that exist individually Poymers large organic molecules form by combining monomers Polymer protein monomer amino acid Polymer nucleic acid monomer nucleotide Cells use common reactions to join monomers dehydration In a dehydration condensation reaction an OH amp H are removed as a water molecule In a hydrolysis reaction components of water are added Carbohydrates function for quick fuel and shortterm energy storage in organisms Monosaccharide s are sugars with 3 to 7 carbon atoms Pentose refers to a 5 carbon sugar Hexose refers to a 6 carbon sugar Disaccharides are 2 monosaccharide s joined by the dehydration reactions ex maltose sucrose lactose Starch amp Glycogen Starch is the storage form of glucose in plants Glycogen is the storage form of glucose in animals l liver stores it and releases it between meals Cellulose is the structural unit in cell walls we do not digest it because of different chemical linkage than starch and glycogen Lipids Do not dissolve in water hydrophobic 3 types 1 Fats oils energy storage 2 Phospholipids form membranes 3 Steroids sex hormone cholesterol 1 Fats l usually of animal origin solid at room temperature store energy and insulate against heat loss Oils plant origin yellow liquid at room temperature Fat molecules triglyceride glycerol backbone 3 fatty acids Hydrocarbons always contain carboxyl group Saturated Unsaturated amp Transfatty acids Fatty acid is a hydrocarbon chain that ends with the acidic group COOH Saturated fatty acids no double bonds between carbon atoms Unsaturated fatty acid One or more double bonds between carbon atoms 2 Phospholipids Contain 2 fatty acids and a phosphate group Phosphate group is polar so molecules are not electrically neutral Phosphate group forms a polar head hydrophilic with a non polar hydrophobic tails Form cellular membranes Spontaneously form bilayer which hydrophilic heads face outward to watery solutions and the tails form the hydrophobic interior 0 Phosphate heads near water 0 Fatty acid tails attracted to one another 3 Steroids Have a backbone of 4 fused carbon rings Ex cholesterol testosterone estrogen Proteins polymers composed of amino acid monomers Amino acids Amino group NH2 Acidic group COOH R group varies Protein Functions Support Enzymes speed up chemical reactions Hormones are chemical messengers Actin and myosin move cells and muscles Some proteins transport molecules in blood Antibodies protect cells Channels allow substances to cross membranes Peptides Polypeptide is a single chain of amino acids A peptide bondjoins two amino acids Protein Organization 1 Primary structure is the linear sequence of the amino acids 2 Secondary structure occurs when backbone takes on certain orientation in space alpha helix beta sheet 3 Tertiary structure is the nal 3dimensional shape of a polypeptide a Maintained by various types of bonding between R groups ex covalent ionic hydrogen disul de bonding etc 4 Quaternary structure is found in proteins with multiple polypeptide chains a Separate polypeptide chains are arranged to give this highest structure A protein is denatured when it loses structure and function this happens when it is exposed to extreme heat or pH changes Nucleic Acids DNA amp RNA both polymers of nucleotides Every nucleotide is a molecular complex of Phosphate Pentose sugar ribose or deoxyribose Nitrogen containing base DNA contains Adenine Thymine Guanine Cytosine I double helix of 2 strands held together by hydrogen bonds A pairs with T and C pairs with G RNA contains Adenine Uracil Guanine Cytosinel single stranded many carry info from DNA to make proteins ATP high energy molecule undergoes hydrolysis and energy is released ATP is the energy quotcurrencyquot of the cell Hydrolysis forms ADP or AMP Copyright The MoGraw Hill Companies Inc Permission required for reproduction or display TABLE 22 lDNA Structure Compared With RlNA Structure DNA RNA Sugar Deoxyribose Ribose Bases Adenine guanine thymine Adenine guanine cytosine uracil cytosine Strands Double stranded with base Single stranded pairing Helix Yes No Cellular Ie vel of organization 3 cell types Prokaryotic lack membrane enclosed structure Eukaryotic possess membrane enclosed cells Archaean qualities of both prokaryotic and eukaryotic cells Cells being small are an advantage for multicellular organisms Nutrients such as glucose can enter the cell Wastes such as C02 can exit the cell 5000 surface area affects the ability to get materials in and out of the cell As cells increase in volume the proportionate amount of surface area decreases For a cube shaped cell Voume increases by the cube of the sides Surface area increases the square of the sides and of sides SO if a cell doubles in size its volume increases 8 fold and its surface area increases 4 fold Plasma membrane Forms boundary between cell and environment regulates entrance and exit in and out of cytoplasm Prokaryotic cells Lack of membrane bound nucleus Have bacteria and archaea Generaly unicellularl may be single cells strings or clusters Not all bacteria cause disesase Structurally simple Eukaryotic cells Structurally complex Have membrane bound nucleus Possess organelles Make up animals plants fungi and protists SOME have cell walls raw materials enter and different departments turn them into various products must also get rid of wastes Pant cells may have a primary and secondary cell wall Lignin is found in secondary cell walls Cellulose and chitin make up fungal cell walls Animal cells DO NOT contain cell wall Nucleus Stores genetic material DNA Contains chromatin a Consists of DNA and associated proteins b Coils and condenses into chromosomes Nucleoplasm semi uid medium in the nucleus Nucleolus Where ribosomal RNA rRNA is made Nuclear envelope membrane that separates nucleus from cytoplasm Nuclear pores openings that permit transport of protein ribosomal subunits and other molecules Copyright l he MicGraw Hill Companies Inc Permission required for reproduction or display TABLE 32 Structures of iEuka r yotic Cells Structure Cell wall absent in animal cells Plasma membrane Nucleus Nucleoli Ribosornes Endoplasmic reticulum Elli Rough ER Smooth ER Composition C ontains p olysacharrides Phospholipid ibilayer with embedded proteins Nuclear envelope nucleop lasm chromatin and nucleoli Concentrated area of chromatin RNA and proteins Protein and RNA in two subunits Membranous attened channels and tubular canals Network of folded membranes studded with ribosomes Network of folded membranes having no ribosomes Eunction Support and protection De nes cell boundary regulates molecule passage into and out of cells Storage of genetic information synthesis of DNA and RNA Ribosomal subunit formation Protein synthesis Synthesis and or modi cation of proteins and other substances and distribution by vesicle formation Folding modi ca tion and transport of proteins Various lipid synthesis in some cells Copyright The MicG raw Hiilil Companies Inc Permission required for reproduction or display r TABLE 3 Structure Golgi apparatus Composition Stack of small membranous sacs Structures of Euka r yotic Ceilils Ewnction Processing packaging and distribution of proteins and lipids Lysosomes Membranous vesicle Intracellular digestion animal cells containing digestive only enzyrn es Vacnoles and Membranous sacs Storage of substances vesicles of various sizes P eroxisomes Membranous vesicle Various metabolic tasks containing specific enzymes Mitochondria Inner membrane Cellular respiration cristae bounded by an outer membrane Chloroplasts Membranous grana Photosynthesis p rimaril y in plant cells Cytoslceleton hounded by two membranes Microtubules inter mediate laments actin laments Shape of cell and movement of its parts Cilia and flagella 9 l 2 pattern of Movement of cell cilia are rare in microtubules plant cells Centriole 9 l 0 pattern of Formation of basai animal cells microtubules bodies only Ribosomes site of protein synthesis Use messenger RNA mRNA as template Composed of 2 subunits o rRNA and proteins Found in groups of polyribosomes attached to endoplasmic reticulum or free in cytoplasm Endomembrane system Consists of nuclear envelope endoplasmic reticulum golgi appartatus and several vesicles Acts as the transportation and productprocessing section of the cell Compartmentalizes cell so that enzymatic reaction restricted to speci c cell sections Endoplasmic Reticulum rough ER and smooth ER Rough ER a Studded with ribosomes b Processing folding and modi cation of proteins Smooth ER a Has no attached ribosomes b Synthesizes phospholipids and steroids c Stores calcium ions d Various other functions depending on cell type Golgi Apparatus a stack of 3 to 20 slightly curved sacs In animal cells one side is directed toward the ER and the other toward the plasma membrane SHPPNG CENTER OF THE CELL Coects sorts packages distributes materials such as proteins and lipids Receives proteins and also lipid lled vesicles that bud from the ER Proteins made in rough ER have tags that serve as quotzip codesquot to direct Golgi apparatus where to send them Lipids and proteins are modi ed in transit through Golgi before being repackaged into secretory vesicles Contents are discharged out of cell by secretion Lysosomes membrane enclosed vesicles formed by the golgi Contain hydrolytic digestive enzymes GARBAGE DISPOSAL OF CELL Breakdown unwanted foreign substances or worn out parts of cell Bring macro molecules into cell Vacuoles Large membranous sacs More prominent in plants Stores substances water pigments toxins Peroxisomes Membrane bound vesicles that contain enzymes derived from cytoplasmic ribosomes 0 Actions of enzymes create hydrogen peroxide 0 Hydrogen peroxide is quickly broken down into water and oxygen by enzyme catalase Functions vary among cells 0 ln liver cells metabolize fats or produce bile o In germinating plant cells they oxidize fatty acids Chloroplasts use solar energy to synthesize carbs and Mitochondria use the breakdown of carbs to produce ATP are organelles that specialize in converting energy into useable forms for the cells Mitochondria Site of cellular respiration Structure a bounded by double membrane b Matrix the inner uid lled space c Cristae formed by invaginations of the inner membrane invaginations INCREASE SURFACE AREA Contain their own DNA Cytoskeleton 3 interconnecting proteins a actin laments b intermediate laments c microtubules Maintains cell shape Assists in movement of cell and organelles Dynamic assembled and disassembled as needed Actin Filaments Two long thin exible actin chains twisted into a helix Functions 0 Provide structure as dense web under plasma membrane 0 Form projections in intestinal cells as microvilli 0 Allow for formation of pseudopods in amoeboid movement Actin interacts with motor molecules for movement ex muscle cells n presence of ATP myosin pulls actin along Intermediate Filaments ntermediate in size between actin laments and microtubules Functions Support nuclear envelope Hep form cell to cell junctions like those holding skin cells together Strengthen human hair Microtubules Hoow cylinders made of globular tubulin Controlled by Microtubule Organizing Center MTOC Most important MTOC is centrosome Func ons Hep maintain cell shape Interact with motor molecules kinesin and dynein to cause movement of organelles Form spindle apparatus during cell division Centrioles Found in centrosomes of animal cells May be involved in microtubule assembly and disassembly Cilia and Flagella paramecia move by means of ciia 41 Plasma Membrane seperates internal environment of the cell from its external environment regulates entrance and exit of molecules in and out of cell to maintain homeostasis Phospholipid bilayer with embedded proteins hydrophiic polar heads face inside and outside of cell where water is present hydrophobic nonpolar tails face each other away from water Cholesterol animal cells controls excess uidity Peripheral proteins associated with only one side of membrane Integral proteins span the membrane Can protrude from one or both sides Embedded within the membrane Able to move laterally Glycolipids lipids attached to carbohydrates Glycoproteins proteins attached to carbohydrates help body realize when it is being invaded by pathogens Channel proteins involved in the passage of solutes through the membrane Substances simply move across the membrane Some may contain a gate that must be opened in response to a signal Carrier proteins allow the passage of a solute by combining with it and help it move across the membrane Enzymatic proteins carry out metabolic reactions directly Plasma membrane is selectively permeable Which molecules that may cross the membrane and which may require carrier proteins depends on sizenature of the molecule polarity charge etc Small uncharged molecules freely cross the membrane by slipping between hydrophilic heads and pass through hydrophobic tails this is driven by the concentration gradient Concentration gradient going quotdownquot a concentration gradient from an area of higher to lower concentration going quotupquot a concentration gradient from an area of lower to higher concentration which requires input of energy Water which is polar would not be expected to readily cross the membrane Aquaporins special channels that allow water to cross the membrane present in the majority of cells Molecules that are large ions or charged may need channel proteins to form a pore through the membrane carrier proteins that are speci c for substance they transport or vesicle formation in endocytosis or exocytosis Copyright The McGraWllill Companies Inc Permission required for reproduction or display FTABME4J Energy Not Required Energy Required Passage of Molleculles into and Out of the Celil Name Direction Requirement Diffusion Toward lower concentration Concentration gradient Facilitated transport Toward lower concentration Channels or carrier and concentration gradient Active transport Toward higher concentration Carrier plus energy Exocytosis Toward outside Vesicle fuses mum plasma membrane Endocvto sis Toward inside Vesicle formation Examples Lipidsoluble molecules and gases Some sugars and some amino acids Sugars amino acids and ions Macromolecules Macromolecules Diffusion movement of molecules from an area of higher to lower concentration Down a concentration gradient Occurs until equilibrium is reached soutions solute and solvent combining Rate of diffusion factors Temperature temp increase rate of diffusion increases Pressure Eectrica currents Molecular size Osmotic pressure pressure that develops in a system due to osmosis the greater the osmotic pressure the more likely it is that the water will diffuse in that direction Osmosis lsotonic solute concentration is equal inside and outside of a cell no net gain or loss of water Hypotonic a solution has a lower solute concentration than the inside of cell cell gains water Turgor pressure keeps plant erect cell wall pushes back Hypertonic a solution has a higher solute concentration than inside of cell cell loses water plasmolysis Carrier Proteins required for Facilitated Transport amp Active Transport Facilitated transport explains passage of molecules such as glucose or amino acids like diffusion no added energy is required because molecules are transported DOWN their concentration gradient also known as facilitated diffusion carrier protein takes small molecules that are not fatsoluble across membrane Active transport primary molecules or ions combine with carrier proteins or pumps Molecules move against concentration gradient Added energy and carrier proteins required ATP is the energy source Active transport NaK pump important for nerve and muscle cells moves Na out and K into cells Uses ATP as energy source ATP hydrolyzed to ADP P phosphate Carrier changes shape after phosphate from ATP attaches and then again after it detaches Active transport secondary Energy provided by a cotransported ion lon is moving by facilitated transport Energy comes from the favorable ion concentration gradient Both bind to the same pump at the same time Both move across the membrane in the same direction Requires glucosesodium symport Requires Na K pump Requires glucose carrier protein Bulk Transport Macromolecules are transported into or out of cells by vesicle formation Macromolecules are too large to be transported by carrier proteins Energy is required to form vesicles Vesicle formation is called membrane assisted transport 0 Exocytosis exit from cell Vesicle fuses with another membrane as movement occurs Vesicle becomes part of that membrane 0 Endocytosis enter into cell Part of plasma membrane invaginates to envelop the substance Membrane then pinches off to form an intracellular vesicle Three types of endocytosis Phagocytosis pinocytosis receptormediated endocytosis Phagocytosis large particulate matter such as food molecules or viruses or whole cells amoeba and macrophages Pin0cyt05is liquids and small particles dissolved in liquid certain blood cells or plant root cells Recept0r Mediated Endocytosis type of speci c membrane assisted transport that involves a receptor protein in the membrane and formation of a coated pit Cell surfaces in animals animal cells have two different types of cell surfaces 0 Extracellular mix outside of cells Meshwork of proteins and polysaccharides closely associated with the cells that produced them Collagen resists stretching Elastin provides resilience Fibronectin is an adhesive protein that links integrin o Junctions occurs between cells 0 Both can associate with the cytoskeleton Cell Division Signal Transduction allows communication between cells and the external environment Aows cells to communicate with other cells 3 steps 1 binding of signaling molecule 2 transduction of the signal 3 response to cell lnterphase 3 stages 1 61 stage before DNA synthesis a Cell doubles its organelles and accumulates material for DNA synthesis 2 5 DNA synthesis a Each chromosome consists of one DNA molecule called the chromatid i After DNA replication each chromosome consists of 2 sister chromatids 3 62 stage after DNA synthesis a The cell synthesizes proteins for cell division Mitotic stage Mitosis division of nucleus fol0W5 interphase 0 sister chromatids separate into daughter chromosomes distributed into 2 daughter nuclei Cytokinesis division of cytoplasm 0 follows mitosis o 2 daughter cells that are identical to the mother cell are the result Cell cycle is controlled by both types of signals Internal signals ensure stages follow normal sequence External signals tell the cell whether or not to divide 3 checkpoints control the cell cycle 61 stops if DNA is damaged G2 stops if DNA did not nish replicating M stops if chromosomes are not going to be properly distributed 0 Checkpoints are critical for preventing cancer development 0 Damaged cell should not complete mitosis Mammalian cells enter the cell cycle only when stimulated by an external factor Growth factors are signals that set into motion the events associated with entering the cell cycle Mitosis maintaining the chromosome number Eukaryotic chromosomes are composed of chromatin Formed from combination of DNA and protein histones Dispersed in a nondividing cell Condensed into compact form for cell division EACH species has a characteristic chromosome number Diploid 2n cells have two a pair of each type of chromosome Human body cells 46 in 23 pairs Haploid 1n cells have half the diploid number of chromosomes Human eggs or sperm 23 or 1 member of each pair Overview of mitosis nuclear division that forms two daughter nuclei with the same number and kind of chromosomes One 2n cell becomes two 2n cells DNA replication produces duplicated chromosomes Each duplicated chromosome is composed of two sister chromatids held together by a centromere 0 Sister chromatids are genetically identical 0 Centromere divides and each chromatid because a daughter chromosome 0 Daughter cell is same as parental cell 0 Spindle brings an orderly distribution of chromosomes to the daughter cell nuclei Mitosis in animal cells Prophase 0 Nuclear membrane disappears centrosomes migrate spindle bers appear o Chromatin condenses and chromosomes become visible 0 Centromeres attach to spindle bers 0 Chromosomes have no particular orientation Metaphase o Spindle fuly forms and consists of poles asters and bers 0 Chromosomes line up at the metaphase pate Anaphase o Centromeres divide sister chromatids are moved to opposite poles by bers Kinetochore spindle bers shorten pulling daughters Polarspindle bers push the poles apart Telophase 0 Nuclear membrane reforms spindle disappears cytokinesis occurs 0 Chromosomes become more diffuse again 0 Nucleolus appears in each daughter nucleus Cytokinesis in Animal Cells Cleavage furrow forms between daughter nucei Contractile ring contracts deepening the furrow Process continues until separation is complete Meiosis Occurs in the life cycle of sexually reproducing organisms Reduces the chromosomes number in half Provides offspring with different combination of traits that that of either parent BEGINS with one diploid parental cell Requires two cell divisions Ends with 4 haploid daughter cells will have half of the chromosomes as parent ce lnvoves pairs of chromosomes caed homologues that are inherited from each parent Each homologue is present as a set of sister chromatids Meiosis I Prophase l Anaphase l Metaphase l Telophase l Heps ensure genetic variation by Crossing over ndependent assortment Homologous sister chromatids line up side by side at the equator synapsis When homologous pairs separate each daughter ce receives one member of the pair The cells are now haploid Prophase l o Synapsis occurs nuclear membrane breaks down 0 Spindle appears nuclear envelope fragments and nucleolus disappears o Homologues line up side by side and crossing over occurs 0 AFTER crossing over chromatids held together are no longidenUcal One has the original genetic material Other has recombined genetic material Metaphase l o Homologous pairs line up at metaphase plate such that maternal or paternal member may be oriented toward either pole 0 Independent assortment occurs when these homologues separate from each other during anaphase generates cells with different combinations of maternal and paternal chromosomes Humans with 23 pairs of chromosomes have 8388608 different possible combinations Telophase l 0 May or may NOT occur at end of meiosis l 0 Nuclear envelopes reform o Nucleoli reappear o Cytokinesis may occur producing two daughter cells which are haploid lnterkinesis 0 Period of time between meiosis l and meiosis II o No replication of DNA Second Division Prophase II 0 Cells have one chromosome from each homologous pair 0 Spindle appears and the nuclear envelope disassembles 0 Each duplicated chromatid attaches to the spindle o Nucleolus disappears Metaphase II 0 Sister chromatids line up at the metaphase plate Anaphase II 0 Sister chromatids separate and become daughter chromosomes that migrate toward the poles Telophase II o Spindle disappears 0 Nuclear envelope reforms o Cytokinesis occurs Importance of meiosis Produces haploid cells from diploid cells Genetic variation produces cells no longer identical to parental cell Genetic variation occurs in 2 ways Crossing over between non sister homologues ndependent assortment of chromosomes during anaphasel During fertilization combining of chromosomes from genetically different gametes help ensure offspring isn t identical to parents Genetic variability is the main advantage of sexual reproduction Longterm genetic variation increases the survival of a species Comparison of meiosis and mitosis Replication occurs only once prior to either mitosis or meiosis Meiosis requires 2 divisions mitosis 1 Meiosis produces 4 daughter cells mitosis produces 2 4 daughter cells from meiosis are haploid 2 from mitosis are diploid Daughter cells from meiosis are genetically variable but from mitosis they are genetically identical Meiosis only occurs at certain times of the life cycle of sexually reproducing organisms Mitosis takes place continually in all tissues as part of growth and repair Meiosis in the testes of males is called spermatogenesis Meiosis in the ovaries of females is called oogenesis Meiosis ll NO replication of DNA occurs between meiosis l and II Centromeres divide and sister chromatids migrate to opposite poles to become individual chromosomes Each of 4 daughter cells produced has the haploid chromosome EACH chromosome is composed of one chromatid Fertilization Daughter cells of meiosis mature into gametes o Sperm and eggs fuse in fertilization Fertilization restores the diploid number n n 2n Creates cell that will develop into new individual Copyright The jI xi39irgt39 uratiriiiIi Companies ioe Permission required for reproduction or display TABLE 51 Comparison of Meiosis i with Mitosis Meiosis ili Mitosis Prop39hose I Prophase Pairing of homologous iNo pairing of chromosomes chromosomes Metaphase I Metaphase Homologous duplicated Chit Duplicated chromosomes at mosomes at metaphase plate metaphase plate Anaphase I Anophng Homologous chromosomes Sister chromatids separate separate becoming daughter chrome somes that move to the poles Tolophase I TelephaseCytakinesis Two haploid daughter cells Two daughter cells identical to the parental cell