Question 1

The __________ causes the catalytic headpiece of ATP synthase to change conformation.

Accepted Answer

The interaction with the rotating central F1F1F1S1F1F1F10 subunit causes the catalytic headpiece of ATP synthase to change conformation. This is because the F1F1F1S1F1F1F10 subunit is directly involved in the catalytic process of ATP synthesis, and its rotation is what drives the conformational changes necessary for ATP synthesis.

Question 2

ATP synthase is located in or on the

Accepted Answer

ATP synthase is located in the inner mitochondrial membrane of the mitochondria. It is responsible for synthesizing ATP from ADP and inorganic phosphate during the process of oxidative phosphorylation, which occurs on the inner mitochondrial membrane.

Question 3

The resting state of the three $\beta$ subunits in the ATP synthase enzyme is best described as

Accepted Answer

The resting state of the F1 portion of ATP synthase typically consists of its three β subunits in different conformations: one in the open (O) conformation, one in the loose (L) conformation, and one in the tight (T) conformation. This arrangement facilitates the enzyme's ability to bind ADP and phosphate, synthesize ATP, and then release the ATP molecule.

Question 4

Which part of the native ATP synthase enzyme is stationary and does NOT rotate during ATP synthesis?

Accepted Answer

The catalytic headpiece of ATP synthase is stationary and does not rotate during ATP synthesis. It is involved in the synthesis of ATP from ADP and inorganic phosphate, while other parts of the enzyme, such as the rotor and the c subunits, rotate to facilitate this process.

Question 5

Which one of the following statements about the glycerol phosphate shuttle is true?

Accepted Answer

The glycerol phosphate shuttle involves the transfer of electrons from cytoplasmic NADH to dihydroxyacetone phosphate (DHAP), converting it into glycerol phosphate. This process is a way for electrons from NADH generated in the cytoplasm during glycolysis to be indirectly transferred to the mitochondrial electron transport chain, albeit with less efficiency compared to the malate-aspartate shuttle.

Question 6

How many ATPs are obtained from one acetyl-CoA run once through the TCA cycle, assuming that all resulting NADH and FADH₂ is used by the electron transport chain and oxidative phosphorylation to make ATP?

Accepted Answer

One acetyl-CoA run through the TCA cycle generates 3 NADH and 1 FADH2. Each NADH can generate 2.5 ATP, and each FADH2 generates 1.5 ATP through oxidative phosphorylation. Therefore, the total ATP generated from one acetyl-CoA run through the TCA cycle is:

3 NADH x 2.5 ATP/NADH = 7.5 ATP
1 FADH2 x 1.5 ATP/FADH2 = 1.5 ATP
Total ATP = 7.5 + 1.5 + 1 (from substrate-level phosphorylation) = 10 ATP.

Question 7

An ATP synthase enzyme with more than 10 c subunits in the F₀ stalk would

Accepted Answer

An ATP synthase enzyme with more than 10 c subunits in its structure would require more protons to complete one 360° rotation because the number of protons needed for a full rotation is directly proportional to the number of c subunits in the enzyme. Each c subunit typically transports one proton across the membrane, so more c subunits mean more protons are needed for the rotation.

Question 8

Which one of the following correctly designates the number of ATPs generated by the reducing molecules shown below?

Accepted Answer

NADH generated in the cytosol and transported into the mitochondria via the malate-aspartate shuttle typically generates about 2.5 ATP, not 1.5. NADH from the TCA cycle also generates approximately 2.5 ATP. The glycerol phosphate shuttle results in the generation of about 1.5 ATP from NADH produced in the cytosol because it transfers electrons to FAD, not NAD+, in the mitochondria. FADH2 from the TCA cycle generates approximately 1.5 ATP, making option D correct.

Question 9

How many ATPs are produced from the complete metabolism of one glucose molecule, assuming that all resulting NADH and FADH₂ is used by the electron transport chain and oxidative phosphorylation to make ATP?

Accepted Answer

The complete metabolism of one glucose molecule produces 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and 28 ATP from oxidative phosphorylation (using the NADH and FADH2 produced in glycolysis and the Krebs cycle). Therefore, the total is 32 ATP.

Question 10

Electrons from a succinate molecule can enter into the ETC and result in enough pumped protons to make how many ATPs?

Accepted Answer

One succinate molecule enters the ETC via complex II, which pumps less H+ than complex I. As a result, only 1.5 ATPs are produced for each pair of electrons entered into the ETC by a succinate molecule.

Question 11

Protons in the mitochondria are

Accepted Answer

Protons in the mitochondria are pumped by mitochondrial electron transport system enzymes. This process creates an electrochemical gradient across the inner mitochondrial membrane, which is used to drive ATP synthesis.

Question 12

What would happen to a mutated ATP synthase enzyme where the proton binding aspartate residue on the c subunits was mutated to an alanine?

Accepted Answer

The proton binding aspartate residue on the c subunits is necessary for the rotation of the rotor and subsequent synthesis of ATP in response to a proton gradient. If this residue is mutated to an alanine, the c subunits would not bind protons and the rotor would not be able to rotate, thus prohibiting the synthesis of ATP in the presence of a proton gradient.

Question 13

What is the driving force for ATP synthesis by the ATP synthase enzyme?

Accepted Answer

The pH gradient across the inner mitochondrial membrane is the driving force for ATP synthesis by the ATP synthase enzyme. This gradient is created by the electron transfers through the protein complexes during oxidative phosphorylation. Choice B is not a valid chemical reaction and choice C refers to a different process in cellular respiration.

Question 14

In yeast, it is estimated that approximately H⁺are required by ATP synthase per ATP synthesized.

Accepted Answer

In yeast, it is estimated that approximately 3 protons (H+) are required by ATP synthase per ATP synthesized. This is a general estimate for the proton motive force needed across the mitochondrial membrane to drive ATP synthesis in eukaryotic cells.

Question 15

The ATP synthase enzyme contains a central stalk embedded in the mitochondrial membrane. What part of this stalk rotates?

Accepted Answer

The ring of c subunits rotates within the membrane, driving the rotation of the central stalk and ultimately leading to ATP synthesis.

Question 16

The catalytic headpiece of the ATP synthase enzyme is primarily composed of which subunits?

Accepted Answer

The catalytic headpiece of ATP synthase, known as the F1 unit, is primarily composed of a hexameric ring of alternating alpha (α) and beta (β) subunits, typically denoted as α3β3.

Question 17

ATP synthesis occurs

Accepted Answer

ATP synthesis occurs at the ATP synthase complex after ADP and Pi are transported into the mitochondria. The electron transfer reactions through complexes I-IV generate a proton gradient across the inner mitochondrial membrane, which drives the synthesis of ATP from ADP and Pi at the ATP synthase complex. Leakage of H+ and K+ ions across the mitochondrial membrane is minimized through the action of ion channels and transporters, and is not a significant source of ATP synthesis. ATP synthesis does not occur on the outer mitochondrial membrane.

Question 18

During transfer of ATP, ADP, and P_i, some of the proton gradient is lost in the

Accepted Answer

The answer of During transfer of ATP, ADP, and P_i,...

Question 19

Which mechanism is the most efficient at moving NADH equivalents from the cytoplasm into the mitochondria?

Accepted Answer

The malate-aspartate shuttle is the most efficient at moving NADH equivalents from the cytoplasm into the mitochondria. This shuttle involves the conversion of malate to oxaloacetate, followed by the conversion of oxaloacetate to aspartate, with the transfer of electrons from NADH to NAD+ in the process. The aspartate molecule can then be transported into the mitochondria, where it is converted back to oxaloacetate and malate, with the transfer of electrons to the electron transport chain. This shuttle is highly efficient because it allows for the transfer of both electrons and the reducing equivalents they represent (i.e. NADH) into the mitochondria, while also allowing for the regeneration of NAD+ in the cytoplasm.

Question 20

What type of transport is illustrated by the mitochondrial ATP/ADP translocase?

Accepted Answer

The mitochondrial ATP/ADP translocase is an antiporter, as it transports ATP out of the mitochondrial matrix while transporting ADP into the matrix in exchange.

Quiz 11: Oxidative Phosphorylation