week 6 Flashcards
Why does oxidative phosphorylation generate more ATP than substrate-level phosphorylation?
A) It produces ATP directly from metabolic intermediates.
B) It exploits a proton gradient to drive ATP synthesis.
C) It does not rely on electron carriers like NADH or FADH2.
D) It generates high-energy phosphate bonds without requiring membrane proteins.
it exploits pmf to generate atp
- substrate level phosphorylation uses an energy rich bond like Acetyl Coa to make ATP directly
ox phos uses pmf to generate atp
what is the difference of the use of the pmf to generate atp in oxidative phosphorylation and photophosphoryalation?
the pmf in ox phosphorylation is generated by transfering electrons,(redox reactions) making it efficient
photophosphorylation is generated by light energy
If a bacterial cell is growing anaerobically using nitrate as a terminal electron acceptor, what is a likely consequence compared to aerobic respiration?
A) ATP yield will be lower due to a smaller proton gradient.
B) ATP yield will be higher because nitrate is a more efficient electron acceptor than oxygen.
C) The cell will rely more on fermentation to generate ATP.
D) The citric acid cycle will be completely shut down.
the ATP yield will be lower due to a smaller proton gradient
Why is NADH a more effective energy carrier than FADH2 in the electron transport chain?
A) NADH donates electrons at a later stage in the chain, generating a larger proton gradient.
B) NADH donates electrons at an earlier stage in the chain, allowing more proton pumping.
C) FADH2 carries more electrons, leading to greater energy loss as heat.
D) FADH2 donates electrons directly to oxygen, bypassing ATP synthesis.
NADH donates electrons at an earlier stage in the chain, allowing more proton pumping.
How does the reduction potential of a molecule influence its role in cellular metabolism?
A) A molecule with a lower reduction potential is more likely to be reduced in redox reactions.
B) A molecule with a higher reduction potential is more likely to donate electrons.
C) A molecule with a higher reduction potential is a stronger electron acceptor.
D) Reduction potential has no effect on metabolic energy production.
A molecule with a higher reduction potential is a stronger electron acceptor.
*A high reduction potential means a species has a strong tendency to gain electrons (be reduced) and acts as a strong oxidizing agent, readily accepting electrons from other substances
Reactions with NAD+/NADH are called hydride transfers
because they transfer:
A.One electron and one proton
B.One electron and two protons
C.Two electrons and one proton
D.Two electrons and two protons
E.None of the above
two electrons and one proton
- a hydride transfer involves the transfer of 1 proton and 2 electrons
A student wrote the following on their exam: “Conversion of ubiquinone to
ubiquinol is an example of a hydride transfer because it involves the
transfer of two protons and two electrons.” What is your assessment of
their statement?
A. The statement is true
B. The statement would be true if “two protons” were changed to “one
proton”
C. The statement would be true if “ubiquinone to ubiquinol” were changed
to “FAD+ to FADH2”
D. None of the above
none of the above
the oxidized form of ubiquinone gains two hydrogen atoms, which transfers (2 protons, and 2 electrons), which is not a hydride transfer (2 electrons, 1 proton)
what is the difference between the transfer of electrons and protons between NADH, FADH, and Coenzyme Q?
NADH involves a hydride shift (2 electrons, 1 proton)
Coenzyme Q and FADH2 involve the gain of 2 electrons and two protons
Enzymes:
A. Change the available energy of a reaction
B. Increase the rate of a reaction
C. Require an initial input of energy to
catalyze a reaction
D. All of the above
E. None of the above
the answer is B
incorrect:
a) enzymes do not alter gibbs free energy
c) does not need an additional input of energy
Mybacter precious lives on rock inside a volcano. What
is it most likely?
A.Chemoorganotroph
B.Chemolithotroph
C.Photoorganotroph
D.Photolithotroph
E.None of the above
a chemolithotroph, since rock is inorganic (no carbon made of minerals) and it does not use light
how do enzymes decrease activation energy?
by…
- dessolvation (removing solvents from water)
- breaking and forming bonds through weak interactions like hydrogen bonds and van der waals
how do enzymes decrease activation energy?
- by increasing concentrations of substrate at the active site of the enzyme
- orient substrates properly to form the transition state complex
- causes dynamic interactions between enzymes and substrate
Where does substrate level phosphorylation occur?
A. Glycolysis
B. TCA cycle
C. Electron transport chain
D. ATP synthase
E. Fermentation
F. Two of the above
G. All of the above
*substrate level phosphorylation is the direct formation of ATP or GTP by transferring a phosphate group from a high energy compound to an ADP or GDP molecule.
glycolysis and TCA cycle
Which of the following is not made directly from
pyruvate?
A. Citrate
B. Alanine
C. Lactate
D. Acetyl-CoA
citrate is the first molecule in the TCA cycled made directly from Acetyl-Coa, which does not directly turn into pyruvate
Why does glycolysis continue under anaerobic conditions even though it is less efficient?
A) Fermentation regenerates NAD+ to keep glycolysis running.
B) The electron transport chain is more active in the absence of oxygen.
C) Pyruvate directly generates ATP in the absence of oxygen.
D) ATP synthase becomes more efficient under anaerobic conditions.
A) Fermentation regenerates NAD+ to keep glycolysis running.
Which of the following explains why ATP synthase requires a proton gradient to function?
A) The movement of protons across the membrane powers conformational changes that drive ATP synthesis.
B) The enzyme requires direct binding of electrons to generate ATP.
C) ATP synthase hydrolyzes ATP to establish a proton gradient before reversing the process.
D) ATP synthase only operates when protons are actively transported by the electron transport chain.
The movement of protons across the membrane powers conformational changes that drive ATP synthesis.
Why is acetyl-CoA central to multiple metabolic pathways?
A) It is a precursor for fatty acid synthesis, steroid synthesis, and energy production.
B) It is only used for ATP production in the citric acid cycle.
C) It is exclusively produced from carbohydrate metabolism.
D) It acts as a terminal electron acceptor in fermentation.
It is a precursor for fatty acid synthesis, steroid synthesis, and energy production.
How does β-oxidation contribute to ATP production?
A) It directly produces ATP by phosphorylating ADP.
B) It generates acetyl-CoA, NADH, and FADH2, which feed into the citric acid cycle and electron transport chain.
C) It breaks down glucose into smaller carbon units for fermentation.
D) It consumes ATP to synthesize fatty acids for later use.
It generates acetyl-CoA, NADH, and FADH2, which feed into the citric acid cycle and electron transport chain.
Why do chemolithotrophs have an advantage in extreme environments?
A) They rely on organic compounds as their primary energy source.
B) They can use inorganic electron donors unavailable to other organisms.
C) They generate more ATP per glucose molecule than chemoorganotrophs.
D) They require oxygen to survive in high-temperature environments.
They can use inorganic electron donors unavailable to other organisms.
Why does aerobic respiration yield more ATP than anaerobic respiration?
because oxygen had the highest reduction potential, leading to a greater proton gradient
Which of the following pathways generate both
acetyl-CoA and NADH?
A. β-oxidation
B. TCA cycle
C. Both
D. Neither
only beta oxidation
In Paracoccus denitrificans, how many protons are transported across
the plasma membrane using the electron transport chain if the
electrons start from succinate dehydrogenase and end up with oxygen?
A. 0
B. 4
C. 6
D. 10
6 because we only account for protons released by NADH
what is the net result of of oxidation phosphorylation in terms of protons?
for every 2 electrons transported from NADH, 10H+ are generated
for every2 electrons transported from FADH2, 6 H+ are generated
what is the purpose of cytochrome c
acts as a transporter for electrons to get to complex 4
