Biology Test 2 Study Guide
Biology Test 2 Study Guide BIO 1134
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This 15 page Study Guide was uploaded by Madison Greer on Thursday February 25, 2016. The Study Guide belongs to BIO 1134 at Mississippi State University taught by Evan Kaplan in Spring 2016. Since its upload, it has received 313 views. For similar materials see General Biology (Lecture) in Biology at Mississippi State University.
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Date Created: 02/25/16
• All living cells are surrounded by a plasma membrane. • This membrane separates internal contents of the cell from external environment. • cell membranes- thin structures made mainly of phospholipids, proteins, and carbohydrates. • Phospholipids are amphipathic; have hydrophilic and hydrophobic regions. • The plasma membrane functions as a selectively permeable barrier that allows passage of oxygen, nutrients, and wastes for the whole volume of the cell. • extracellular ﬂuid- outside of cell • intracellular ﬂuid- inside the cell • The membrane is not just phospholipids; many other molecules makeup the cell membrane. • The overall structure of membranes is referred to as the ﬂuid-mosaic model. • Membranes are mainly composed of: phospholipids, carbohydrates, and proteins. • The proteins can span across the membrane and/or loosely bound to the outside or inside of the membrane and thus not part of the membrane structure. • phospholipids- structurally similar to triglycerides, but phospholipids have 2 fatty acid chains and a phosphate group where as triglycerides have three fatty acid chains. • The phosphate group on the end of the phospholipid is negatively charged causing that end to form a polar covalent bond with glycerol. • One end of the phospholipid id polar and the other is non-polar. • The polar end of the molecule is negatively charged and the non-polar end is positively charged. • Since water is also polar, the polar end of the phospholipid is attracted to the positive ends of water molecules. (hydrophilic) • The neutral end of the phospholipid is non-polar and is repelled by the water molecules. (hydrophobic) • The plasma membrane isn't rigid. It moves and sways. Imagine a water bed. This is called ﬂuidity. • The individual molecules remain close but can readily move within the membrane. • These molecules are held together with relatively weak hydrophobic interactions. • Most lipids can drift laterally through the membrane but they can also ﬂip-ﬂop. • lipid component in the membrane- synthesized in the smooth ER, transported by the Golgi, lysosomes, vacuoles, or plasma membrane • lipid exchange proteins- can take a lipid from one protein to another • protein component in the membrane- comes from the endomembrane system organelles • rough ER-> Golgi-> plasma membrane • Cells have to transport materials (nutrients and waste) in and out to survive. • Transport mechanisms • passive transport (by diffusion) + + 2+ • facilitated transport- large molecules, such as K , Na , and Ca , diffuse passively through channel transport proteins • osmosis- diffusion of water • active transport- movement of a solute across a membrane against its concentration gradient, uses energy • primary active transport- requires energy to move solute against concentration gradient secondary active transport- pre-existing gradient drives active transport of • another solute • exocytosis- involves packaging material inside the cell into vesicles and the excrete the material outside the cell • endocytosis- plasma membrane folds inward to form a pocket, resulting in an internalized vesicle that brings substances into the cell • three types of endocytosis • receptor-mediated endocytosis • pinocytosis (“cell- drinking”) • phagocytosis (“cell-eating”) • aA+bB=cC+dD • A and B are reactants • C and D are products • a, b, c, and d are the number of moles • energy- the ability to promote change or to do work • two forms of energy • kinetic energy- energy associated with movement • potential energy- stored energy due to structure or location • chemical energy is a form of potential energy contained within covalent bonds • thermodynamics- the study of energy • 1st law- energy can neither be created nor destroyed • 2nd law- any energy transfer or transformation from one form to another increases the degree of disorder of a system • entropy- the measure of randomness of molecules in a system • The sun provides energy (light energy) to all living systems on the planet. • Cells do three main types of work • mechanical work- movement of cilia and ﬂagella, contraction of muscle cells, and movement of chromosomes • transport work- pumping substances across membranes against the direction of spontaneous movement • chemical work- involving stockpiling, building, rearranging, and breaking apart substances • ATP- energy that powers cellular work; a nucleotide consisting of ribose, adenine, and a chain of three phosphates; can be broken into ADP • The phosphate bonds of ATP are weak covalent bonds. • The ATP Cycle- ATP is a renewable that is continually regenerated by adding a phosphate group to ADP • enzymes- catalysts that speed up the rate of chemical reactions that perform at normal body temperature • Enzymes DON’T change anything other than the time it takes for a reaction to occur. They just make it faster! • activation energy- needed to initiate a chemical reaction • active site- a speciﬁc location on the enzyme for the reactants to bind to • enzyme inhibitors- prevent enzymes from catalyzing reactions • Enzymes are affected by concentration, temperature, and pH. • Temperature has a major impact on reaction site. • metabolism- the sum total of all chemical reactions that occur within an organism • metabolic pathway- a sequence of steps that chemical reactions happen in • Two types of metabolic pathways involving energy • catabolic pathways- breakdown larger molecules into smaller ones to produce energy (hydrolysis) • cellular respiration • anabolic pathways- synthesize larger molecules from smaller ones and requires energy to do so (dehydration) • photosynthesis • Metabolic pathways are tightly regulated in three ways • gene regulation- allows cells to make or inhibit enzymes involved in metabolic pathway • cellular regulation- environmental signals activate/inactivate cell • biochemical regulation- a molecule noncovalently binds to enzyme to activate or inhibit that enzyme • All living organisms require a constant supply of energy to sustain life. • energy from sun -> chemical energy via photosynthesis • Complex chemical reactions occur in a number of separate stages. • Each reaction is catalyzed by a speciﬁc enzyme. • Metabolic pathways are similar in all organisms, from bacteria to humans. • oxidation-reduction (redox) reactions- break down organic molecules; transfer one or more electrons from one reactant to another • oxidation- loss of electrons • reduction- addition of electrons • Ae- + B -> A + Be- (redox reaction)- A, the electron donor, is the reducing agent and reduces B. B, the electron recipient, is the oxidizing agent and oxidizes A. The transfer electron carries energy with it. • In cellular respiration, glucose and other fuel molecules are oxidized, realizing energy. • As glucose is oxidized, the electrons get passed to a ﬁnal electron acceptor. • Cellular respiration doesn’t transfer hydrogen from glucose to oxygen all at one time. Hydrogen atoms are stripped from glucose and transferred to electron carriers. • electron carriers- NAD+ (nicotinamide adenine dinucleotide) and FAD+ (ﬂavin adenine dinucleotide) • Electron carriers deliver hydrogen to the ﬁnal step of the respiration process resulting in the majority of ATP. • Oxidation reactions occur in a speciﬁc order; it begins in the cytoplasm and is completed in the mitochondria. • Three main stages and one intermediate stage: • glycolysis- begins the breakdown of glucose; occurs with or with out oxygen • breakdown of pyruvate via oxidation (intermediate stage) • citric acid cycle (Kreb’s cycle or TCA (tricarboxylic acid cycle)) • oxidative phosphorylation via electron transport chain • cellular respiration- involves the breakdown of glucose (and other organic molecules) in the presence of oxygen (aerobic) • simpliﬁed equation of cellular respiration: glucose + oxygen -> -> -> -> carbon dioxide + water + energy • Glycolysis • As glucose is broken down, hydrogen atoms are stripped from glucose and passed to NADH. • energy investment phase- ATP energy activates glucose and its six-carbon derivatives • pyruvate- 6-carbon glucose is broken down into 2 three-carbon molecules in the cytoplasm • energy liberation phase- the products of the ﬁrst part are split into three-carbon pyruvate molecules; 4 ATP formed by substrate-level phosphorylation, 2 NADH formed • If oxygen is present, pyruvate is transported into the mitochondrion where enzymes of the Kreb’s cycle complete the oxidation of glucose to carbon dioxide. • Citric Acid Cycle • begins when the acetyl group from acetyl CoA combines with oxaloacetate to form citrate. • each cycle produces 1 ATP by substrate-level phosphorylation, 3 NADH, and 1 FADH2 per acetyl CoA • The Electron Transport Chain • All the NADH and FADH2 produced in glycolysis go to the electron transport chain. • vast majority of ATP produced from the oxidation of glucose comes from the energy in the electrons carried by NADH and FADH2 • the ETC generates no ATP directly • ATP Synthase- the only way for H+ to get back into the matrix; as H+ passes through, it leads to generation of ATP by ATP Synthase • chemiosmosis- the movement of ions across a selectively permeable membrane, down the electrochemical gradient. • ATP yield- the theoretical yield of ATP is 36-38; the actual yield is closer to 30 • regulation of aerobic respiration • negative inhibition- the end product feedbacks and inhibits an enzyme that catalyzes an early str in that pathway • ATP and citrate • positive feedback- the reactant activates an enzyme that catalyzes an early step in that pathway • AMP • Molecules such as proteins, fats, and nucleic acids can also be used as sources of energy. • proteins are broken down into their individual amino acids • fats are broken down into glycerol and fatty acids • nucleic acids are broken down into nucleotides • DON’T FORGET… polysaccharides are broken down into glucose • anaerobic respiration- absence of oxygen, sugars can occur by fermentation • examples of fermentation • lactate or lactic acid fermentation- the pyruvate from glycolysis is converted to lactate/lactic acid • some fungi and bacteria used to make cheese, yogurt, and sour cream • causes our muscles to be fatigued and sore • ethanol fermentation- pyruvate is covered to ethanol and carbon dioxide • some yeast and plant cells use in the absence of oxygen • used in brewing, wine-making, and bread- making • photosynthesis- plants, algae, and some bacteria can convert light energy to chemical energy; takes place in the chloroplasts • Sugar made in the chloroplasts supplies the entire plant with chemical energy and carbon skeletons to synthesize all the major carbon-containing molecules for its cells • Photosynthetic organisms produce their own organic molecules (carbs) and use them to make ATP. • Photosynthesis takes place in two stages: • capturing energy from sunlight and using this energy to make ATP, NADPH, and O2. • using the ATP, NADPH, and CO2 to power the synthesis of organic molecules • Pigments inside the chloroplasts capture light energy and use it to drive photosynthesis • chlorophyll a and b- green • other pigments- carotenoids and xanthophylls • Two pathways of photosynthesis • light reactions: driven by light energy- produces ATP and NADPH + H+ • the Calvin Cycle: does not use light directly (sometimes called dark reactions)- uses ATP, NADPH + H+ and CO2 to produce sugars • the two are linked by the exchange of ATP, ADP, NADP+, and NADPH • The Greenhouse Effect • CO2 released into the atmosphere acts like glass in a greenhouse; it allows solar energy to pass through and reach the Earth’s surface, but it absorbs and is heated by the energy that radiates back from the Earth’s surface • As CO2 levels increase, so does the Earth’s temperature • CO2 is produced from fossil fuels used in power plants, factories, and automobiles. • cellular reproduction- essential for replacing dead cells, growth of an organism, and wound healing • Four events must occur for cell reproduction • reproductive signal • DNA replication • distribution or segregation DNA • physical division of cells (cytokinesis) • Chromosomes are inherited in sets; after replication chromosomes consist of two sister chromatids which contain identical copies of the chromosome’s DNA • as they condense, the region where the strands connect shrinks to a narrow area, called the centromere • Humans have 23 pairs of chromosomes that vary in shape and size • karyotype- visualization of the different numbers, shapes, and sizes of chromosomes • Every eukaryotic species has a characteristic number of chromosomes in the nucleus. • humans have 46; we inherit 23 from each parent • Sperm or egg cells only have one set of chromosomes: 22 autosomes and 1 sex chromosome (X orY) • haploid- cell with a single set of chromosomes; n=23 for haploid number for humans • a fertilized egg has two haploid sets of chromosomes (one from each parent) • diploid cells- cells with two sets of chromosomes; 2n=46 for humans • Cell division requires the distribution of identical genetic material, DNA, to two daughter cells. • mitosis- the process of cell division in somatic (body) cells • meiosis- cell division in sex cells (cells that produce gametes, egg and sperm) • Cell division is part of a larger pathway called the cell cycle. • Interphase- ﬁrst step of the cell cycle; cells are engaged in their metabolic activities such as photosynthesis, muscle cell contractions, etc.; cell prepares for the cell division phase; the longest part of the cell cycle • G1- RNA molecules, proteins, and enzymes are being made; cell is growing • S- DNA replication • G2- the ﬁnal preparations for mitosis • preparation for cell division- prior to DNA replication, the DNA of each eukaryotic chromosome consists of a linear DNA doubt helix that is found in the nucleus and is not highly compacted; when a cell is ready to divide, the sister chromatids become tightly packed and readily visible under microscope • Mitotic/Meiosis- second step of the cell cycle; consists of sub phases involved in the physical process of one cell producing two or four daughter nuclei. • prophase • duplicated chromosomes are condensed and become visible • nuclear envelope begins to disappear • spindle microtubules begin to form and capture chromosomes • chromatids are still attached to the centromere • centrioles move to opposite poles • metaphase • nuclear envelope has disappeared • centrioles are at opposite poles • chromosomes are attached to the spindle causing them to be lined up at the metaphase plate • each chromosome still has two chromatids • in human cells there are 46 chromosomes, or 92 chromatids • anaphase • centromeres split and chromatids separate • each chromatid is now termed a chromosome • chromatids move to opposite poles by spindle ﬁbers • each chromatid moving to the opposite pole is the exact copy of the other one • telophase • each set of chromosomes decondense/unwinds • spindles disassemble • nuclear envelope re-forms around each of the two sets of chromosomes • cytokinesis or equal division of the cell cytoplasm takes place • each of the daughter cells formed can now inert G1 stage of interphase and the cycle repeats. • cytokinesis- the division of the cell to form daughter cells; division of the cytoplasm • For the most part, plant and animal cells have very similar cell division cycles • plant cells do not have centrioles, but are still able to produce the spindle ﬁbers • there is a difference in the process of cytokinesis; animal cells form a cleavage furrow and plant cells form a cell plate • The cell cycle is highly regulated and the frequency of cell division varies with cell type. • Three irreversible checkpoints: • G1- determines if conditions are favorable for cell division • G2- makes sure that the DNA was replicated and there is no damage • Metaphase- senses the integrity of the spindle apparatus and all chromosomes attached • the cell cycle can be put on hold at checkpoints • Meiosis is a reduction division (2n -> n) • Meiosis starts with replicated chromosomes composed of two chromatids that go through two consecutive divisions that end with four haploid cells • meiosis 1 • prophase 1 • individual chromosomes become visible • nuclear envelope begins to breakdown • centrioles move to opposite poles • spindles begin to form • homologous chromosomes pair with one another (synapsis) • crossing over may occur • metaphase 1 • synapsed pairs of chromosomes move to the equatorial plate • centromeres of each chromosome are attached to the spindle • the differences from mitosis is that the homologous chromosomes are still attached • chromosomes randomly align along the metaphase plate • anaphase 1 • during this stage, the chromosome number is reduced from diploid to haploid • each pair of homologous chromosomes move to opposite poles • each chromosome is independently attached to a spindle at the centromere • the centromeres do not replicate at this stage • telophase 1 • chromosomes uncoil and become long, thin threads • the nuclear envelop reforms around each new set of chromosomes • cytokinesis divides the cell into two daughter cells • meiosis 2 • the two daughter cells formed in meiosis 1 undergo another division in meiosis 2 • prophase 2 • the nuclear envelope breaks down • the spindles are formed • metaphase 2 • this will be typical metaphase because the chromosomes are attached by their centromeres to the spindle • the chromosomes move to the equatorial plate • pairs of chromosomes are not attached, therefore, each chromosome moves as a separate unit • chromosomes randomly align • anaphase 2 • the difference between anaphase 1 and 2 is in anaphase 2, the centromere of each chromosome divides • the chromatids (daughter chromosomes) move to the opposite poles as in mitosis • there are no paired homologous at this stage • telophase 2 • nuclear envelope forms • chromosomes uncoil, nuclei reform • the spindles disappear • cytokinesis occurs • four haploid cells are formed (egg or sperm) • in humans and other organisms only one functional egg is produced; the other three (known as polar bodies) disintegrate. • nondisjunction- failure of chromosomes to move to opposite poles during anaphase 1 or 2 • Downs Syndrome- an extra 21 chromosome • Klinefelter’s Syndrome- XXY in males; have male sex organs but are infertile • XYY condition- males can have an extra Y chromosome; generally normal (can be taller) • XXX Syndrome- generally normal; can be taller • Turner Syndrome- inheritance of only one X • 98% spontaneously aborted • survivors are short, infertile females • Differences in mitosis and meiosis • chromosome number is halted in meiosis • mitosis produces genetically identical daughter cells • meiosis produces cells that are different from parent cells and each other • mitosis- one division resulting in two genetically identical cells • meiosis- two consecutive divisions resulting in four cells that are not genetically identical
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