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18 Cards in this Set
- Front
- Back
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What is the main form of energy used by cells? What are three other examples?
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ATP; the prime energy currency
– Phosphoenolpyruvate – Glucose 6-phosphate • Chemical energy also stored in coenzyme A |
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What are the two types of ATP Generation?
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1. Substrate-level phosphorylation
2. Electron transport phosphorylation( AKA Respiration-linked phosphorylation) |
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What happens during SLP?
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ATP synthesis by direct transfer of a “high energy” phosphate group from a phosphorylated (activated) organic compound to ADP.
-Electrons are transferred to NAD+ in an oxidation-reduction step that precedes SLP ATP synthesis occurs by SLP at specific enzymatic steps in Glycolysis |
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When does Electron transport phosphorylation occur?
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Respiration
Photosynthesis |
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What are the four main requirements for the electron transport system(ETS)
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cytoplasmic membrane
electron transport chain->redox reaction proton + charge gradient -> pmf membrane-bound ATP synthase->ATP |
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What are the two half step reactions in redox reactions
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Electron donor: the substance oxidized in a redox reaction
• Electron acceptor: the substance reduced in a redox reaction |
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What is Reduction potential (E0′) and what unit is it expressed in?
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Reduction potential (E0′): tendency to donate electrons
– Expressed as volts (V) |
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Reduced substance of a redox couple with a
more__________(negative/positive) E0′ donates electrons to the oxidized substance of a redox couple with a more_________(negative/positive) E0′ |
Reduced substance of a redox couple with a
more NEGATIVE E0′ donates electrons to the oxidized substance of a redox couple with a more POSITIVE E0′ |
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What is Free Energy and what does the +/- sign indicate
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Free energy change (Delta(G)) is the amount of energy in a system that is available to do work
– A negative Delta(G) indicates that the reaction is favorable and will proceed spontaneously (i.e., the reaction is exergonic) – A positive Delta(G) indicates that the reaction is unfavorable and will only proceed if energy is supplied (i.e., the reaction is endergonic) |
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What are some features of the Electron Transport Systems
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– Membrane associated
– Mediate transfer of electrons – Conserve some of the energy released during transfer and use it to synthesize ATP – Many oxidation–reduction enzymes are involved in electron transport (e.g., NADH dehydrogenases, flavoproteins, iron–sulfur proteins, cytochromes) |
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What is NAD?
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(nicotinamide adenine dinucleotide): NAD+ is an electron plus proton carrier, transporting 2 electrons and 2 protons at the same time
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What is a Flavoprotein?
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Flavoproteins: contains flavin prosthetic group (e.g., flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN)) that accepts 2 electrons and 2 protons but only donates the electrons to the next protein in the chain
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What are Cytochromes?
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proteins containing an iron-porphyrin ring
called heme • Accept and donate a single electron via the iron atom in heme • Several classes, differ in reduction potential. Cytochrome a, b, c, etc |
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What are Iron–Sulfur Proteins? What are their purpose?
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Contain clusters of iron and sulfur
• Example: ferredoxin • Can be 2Fe/2S or 4Fe/4S. Reduction potentials vary depending on number and position of Fe and S atoms • Carry electrons |
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What are Quinones? What are some examples? What is unique about them?
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Hydrophobic non-protein containing molecules that
participate in electron transport. • Ubiquinones (Q) (CoenzymeQ) • Menaquinone (MQ) • Lipid soluble • Accept electrons and protons but pass along electrons only |
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What happens during the The Proton Motive Force?
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During electron transfer, several protons are
released on outside of the membrane – Protons originate from NADH and the dissociation of water • Results in generation of pH gradient and an electrochemical potential across the membrane (the proton motive force) |
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Structure and function of ATP synthase (ATPase)
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ATP synthase (ATPase): complex that converts proton motive force into ATP; two components
F1: multiprotein extramembrane complex, faces cytoplasm Fo: proton-conducting intramembrane channel ATPase is reversible!!! |
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Inhibitors of ATP synthesis fall into two
main categories 1) 2) |
a. Blockers (inhibitors) that inhibit the flow of electrons through the system.
• Carbon monoxide, cyanide bind to cytochromes b. Uncouplers that allow electron flow, but disconnect it from oxidative phosphorylation • Dinitrophenol, lipid soluble make membrane leaky and destroy the PMF and ATP production by oxidative phosphorylation. |
