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59 Cards in this Set
- Front
- Back
All biological energy is derived from ___/___ reactions
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oxidation/reduction.
Electrons released during oxidation of chemical energy sources must be accepted by an electron acceptor. Micros. vary in terms of the acceptors they use. |
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Exogenous electron acceptors
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?
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Aerobic respiration
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Enery source degraded using oxygen as terminal (exogenous) electron acceptor. Yield large amount of energy, primarily by e transport activity.
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Anaerobic respiration
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Eneryg source oxidized and degraded using molecules other than oxygen as terminal (exogenous) electron acceptors, e.g, nitrate or sulfate.
Can yield large amt of E |
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Fermentation
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Energy source oxidized and degraded using an organic compound as the electron acceptor. Occur under anaerobic conditions.
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Overview of aerobic catabolism
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large molecules (polymers)->small molecules (monomers)
inital oxidation and degradation to pyruvate oxidation and degredation of pyruvate by the tricarboxylic acid cycle (TCA cycle) |
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Three stages of catabolism
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Fig. 9.3
Many different energy sources are funneled into common degradative pathways. Macromolecules. Degradation to pyruvate. TCA. |
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What is an amphibolic pathway?
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Function both as catabolic and anabolic pathways.
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Three common routes for the breakdown of glucose to pyruvate
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(1)Embden-Meyerhof pathway (glycolysis)
(2) Pentose phosphate pathway (hexose monophosphate shunt) (3) Entner-Doudoroff pathway |
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Glycolysis
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Fig. 9.5
Addition of phosphates "primes the pump" Oxidation step-generates NADH High-energy molecules used to synthesize ATP by substrate-level phosphorylation |
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Why would an organism have both the pentose phosphate and the Embden-Meyerhof pathways?
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?
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Pentose phosphate pathway
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Fig. 9.6
Oxidation steps. Produce NADPH, which is needed for biosynthesis. Produce ribulose-5-P, precursors for nucleic acids. Produce sugars needed for biosynthesis. |
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Entner-Doudoroff Pathway
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Reactions of pentose phosphate pathway
Reactions of glycolytic pathway Yield per glucose molecule: 1 ATP, 1 NADPH, 1 NADH |
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Tricarboxylica acid cycle
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Also called citric acid cycle and Kreb's cycle.
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Amphibolic
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provides carbon skeletons for biosynthesis
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Kreb's cycle
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oxidation steps-form NADH & FADH2.
Substrate-level phosphorylation |
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What is an electron transport system?
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Series of electron carriers that operate together to transfer electrons from NADH and FADH2 to a terminal electron acceptor.
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Electron transport chain
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As electrons transferred, energy is released. Some released energy used to make ATP by oxidative phosphorylation.
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How do the electron transport systems of procaryotes differ from those of eucaryotes?
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Located in cell membrane. Some resemble mitochondrial ETC, but many are diff; diff e- carriers, may be branched, may be shorter.
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Upper branch
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Stationary phase and low aeration
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Lower branch
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Log phase and high aeration
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What is oxidation phosphorylation?
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Chemiosmotic hypothesis is the most widely accepted explanation of oxidative phosphorylation. Postulates that energy released during e- transport used to establish a proton gradient and charge difference across membrane. Called proton motive force (PMF).
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The proton motive force drives ATP synthesis
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movement of protons back across membrane (down gradient) drives formation of ATP.
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ATP synthase (synthetase)
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enzyme that uses proton movement down gradient to catalyze ATP synthesis
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Chemiosmoss (same in pro as mito)
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Movement of protons establishes PMF. ATP synthase uses proton flow down gradient to make ATP.
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Anaerobic respiration
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Uses inorganic electron acceptors other than O2. Generally yields less enery becuase E0 of electron acceptor is less positive than E0 of O2.
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Dissimilatory nitrate reduction
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Use of nitrate as terminal electron acceptor. Denitrification.
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Denitfification
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Reduction of nitrate to nitrogen gas. In soil, causes loss of soil fertility.
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Assimilatory nitrate reduction
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Use to nitrate as nitrogen source
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ETC of Paracoccus denitrificans
Aerobic or anaerobic? |
Aerobic
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ETC of P.denitrificans
Aerobic or anaerobic? |
Anaerobic
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Fermentations
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Oxidation of NADH produced by glycolysis. Pyruvate or derivative used as endogenous electron acceptor. ATP formed by substrate-level phosphorylation.
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Some common microbial fermentations
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Homolactic fermenters
Alcoholic fermentation |
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Methyl red test
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Detect pH change in media caused by mixed acid fermentation
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Strickland reaction
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Oxidation of one amino acid with use of second amino acid as electron acceptor
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What is a Strickland reaction?
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?
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Catabolism of carbohydrates and intracellular reserves
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Many diff carbs can serve as energy source. Carbs can be supplied externally or internally
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Carbohydrate catabolism
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Monosaccharides
-converted to other sugars that enter glycolytic pathway Disaccharides & polysaccharides -cleaved by hydrolases or phosphorylases |
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Give some examples of compounds used as stored energy
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-glycogen and starch; cleaved by phosphorylases. gluocse-1-P enters glycolytic pathway
-PHB and other poly-alkanoates; acetyl-CoA enters TCA cycle |
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What is chemolithotrophy?
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Oxidation of inorganic molecules. Carried out by chemolithotrophs. Electrons released from energy source. ATP sythesized by oxidative phosphorylation
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Chemolithotrophs are usually aerobic or anaerobic?
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Aerobic
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Describe the electron transport system of ammonia-oxidizing bacteria
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?
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What is meant by reverse electron flow?
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?
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Metabolic flexibility of chemolithotrophs
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Many switch from chemolithotropic metabolism to chemoorganotrophic metabolism
Many switch from autotrophic metabolism (via Calvin Cycle) to heterotrophic metabolism |
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Autotrophic growth by chemolithotrophs
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Calvin cycle requires NADH as electron source for fixing CO2. Many energy sources used by chemolithotrophs have E0 more positive than NAD/NADH. Use reverse electron flow to generate NADH.
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Distinguish between the light and dark reactions of photosynthesis
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light reactions; in which light E is trapped and converted to chemical energy
dark reactions; in which the energy produced in the light reactions is used to reduce CO2 and synthesize cell constituents |
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Photosynthesis
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Energy from light trapped and converted to chemical energy
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Oxygenic Photosynthesis
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Eucaryotes and cyanobacteria
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Anoxygenic photosythesis
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All other bacteria
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Chlorophylls
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Major light-absorbing pigments
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Accessory pigments
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Transfer light energy to cholorphylls. e.gm carotenoids & phycobiliproteins
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Antennas
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Highly organized arrays of chlorophylls and accessory pigments
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Photosystems
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Antenna and its associated reaction center chlorophyll
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Green plate photosynthesis
Procaryotes |
Cyclic electron flow; ATP + NADHPH made (cyclic phosphosphorylation)
Plants & cyanobacteria noncyclic electron flow- ATP made (noncyclic phosphorylation) |
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How does anoxygenic photosynthesis differ from plant photosynthesis?
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H2O not used as an electron source; therefore O2 is not produced. Only one photosystem involved. ???
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Describe the difference between photoosynthesis in the nonsulfur purple bacteria and the green sulfur bacteria
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?
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Succinate fumarate
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Electron source for generation of NADH by reverse electron flow
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Reverse electron flow
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ATP or PMF used to drive "upward" (reverse) flow of electrons
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Green sulfur bacteria
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Uses hydrogen sulfide as the electron donor
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