MODULE 12: Chapter 11.4

Question 1

What is a key element of the chemiosmotic theory?

Answer 1

The inner mitochondrial membrane must be impermeable to ions.

Question 2

What are the two translocase proteins responsible for transporting ATP, ADP, and Pi across the inner mitochondrial membrane?

Answer 2

• ATP/ADP translocase
• Phosphate translocase

Question 3

What does the ATP/ADP translocase export and import?

Answer 3

Exports one ATP for every ADP that is imported.

Question 4

How does the phosphate translocase function?

Answer 4

Translocates one Pi and one H⁺ into the matrix by an electrically neutral import mechanism.

Question 5

What mechanism does the ATP/ADP translocase use to exchange ADP for ATP?

Answer 5

A ‘rocking bananas’ mechanism based on protein conformation.

Question 6

What are the conformations of the ATP/ADP translocase called?

Answer 6

• C state (cytosolic)
• M state (mitochondrial or matrix)

Question 7

What effect do the poisons atractyloside and bongkrekic acid have on ATP/ADP translocase?

Answer 7

• Atractyloside blocks ADP binding in the C state
• Bongkrekic acid inhibits ATP binding in the M state

Question 8

What is the charge differential created by the antiport translocation of ADP and ATP?

Answer 8

−1 in the direction of the cytosol.

Question 9

How does the phosphate translocase act as a symporter?

Answer 9

Translocates H2PO4− (Pi) and H⁺ across the membrane together.

Question 10

What is the net flow of H⁺ required for every ATP synthesized in the mitochondrial matrix?

Answer 10

4 H⁺

Question 11

What is the primary shuttle system in liver cells for transferring electrons from cytosolic NADH to mitochondrial NAD⁺?

Answer 11

Malate–aspartate shuttle.

Question 12

What are the four key steps of the malate–aspartate shuttle?

Answer 12

• Reduction of oxaloacetate to malate
• Transport of malate into the mitochondrial matrix
• Transamination of oxaloacetate to form α-ketoglutarate and aspartate
• Transamination of aspartate to form oxaloacetate and glutamate

Question 13

What happens to the direction of reducing equivalents in the malate–aspartate shuttle?

Answer 13

Driven by the cytosolic ratio of NADH and NAD⁺.

Question 14

Which shuttle system do muscle cells use to deliver electrons from NADH to the mitochondrial matrix?

Answer 14

Glycerol-3-phosphate shuttle.

Question 15

What is the main difference between the malate–aspartate shuttle and the glycerol-3-phosphate shuttle?

Answer 15

Glycerol-3-phosphate shuttle enters the electron transport system through coenzyme Q.

Question 16

What are the three main steps of the glycerol-3-phosphate shuttle?

Answer 16

• Reduction of dihydroxyacetone phosphate to glycerol-3-phosphate
• Reoxidation of glycerol-3-phosphate to dihydroxyacetone phosphate
• Transfer of 2 e− to Q

Question 17

What is the net ATP yield from glucose oxidation in liver cells using the malate–aspartate shuttle?

Answer 17

32 ATP.

Question 18

What is the net ATP yield from glucose oxidation in muscle cells using the glycerol-3-phosphate shuttle?

Answer 18

30 ATP.

Question 19

What role does lactate dehydrogenase or alcohol dehydrogenase play under anaerobic conditions?

Answer 19

Replenishes NAD⁺ for glycolysis.

Question 20

True or False: The glycerol-3-phosphate shuttle is faster than the malate–aspartate shuttle.

Answer 20

True.

Question 21

Fill in the blank: The malate–aspartate shuttle ensures that the supply of _______ for the glyceraldehyde-3-phosphate dehydrogenase reaction is maintained.

Answer 21

NAD⁺

Question 22

What is the net yield of ATP from the oxidation of 10 NADH?

Answer 22

25 ATP in liver cells, 23 ATP in muscle cells

The difference in ATP yield is due to the NADH shuttle systems used in liver and muscle cells.

Question 23

How many ATP are generated from glycolysis?

Answer 23

2 net ATP

Glycolysis also produces 2 NADH.

Question 24

What does the pyruvate dehydrogenase reaction produce from 2 acetyl-CoA?

Answer 24

2 NADH

This reaction occurs inside the mitochondrial matrix.

Question 25

What are the products of the citrate cycle?

Answer 25

* 6 NADH * 2 FADH2 * 2 ATP (GTP) ## Footnote The citrate cycle occurs in the mitochondrial matrix.

Question 26

How many total NADH are generated from glucose oxidation?

Answer 26

10 NADH ## Footnote This includes 8 NADH from the mitochondrial processes and 2 NADH from glycolysis.

Question 27

What is the ATP synthesis ratio for NADH?

Answer 27

2.5 ATP per NADH ## Footnote This is based on the translocation of 10 H⁺ out and 4 H⁺ in to synthesize each ATP.

Question 28

What is the ATP synthesis ratio for FADH2?

Answer 28

1.5 ATP per FADH2 ## Footnote This is due to the translocation of 6 H⁺ out and 4 H⁺ in to synthesize each ATP.

Question 29

What is the role of the ATP/ADP translocase?

Answer 29

Exports ATP from the mitochondrial matrix while importing ADP ## Footnote It functions as an antiporter membrane transport protein.

Question 30

What is the malate–aspartate shuttle?

Answer 30

A mechanism used in liver cells to transfer NADH formed in glycolysis into the electron transport system ## Footnote This involves the activity of cytosolic and mitochondrial malate dehydrogenase.

Question 31

What is the glycerol-3-phosphate shuttle?

Answer 31

A mechanism used in muscle cells that transfers NADH electrons to FAD, forming FADH2 ## Footnote This occurs in the mitochondrial intermembrane space.

Question 32

Why does glucose oxidation in muscle cells produce two fewer ATP than in liver cells?

Answer 32

Due to the glycerol-3-phosphate shuttle used in muscle cells ## Footnote This shuttle transfers electrons to FAD instead of NADH, bypassing complex I.

Question 33

What is the effect of ML316 on yeast ATP synthesis?

Answer 33

Inhibits ATP synthesis without blocking ATP synthase directly ## Footnote ML316 targets the yeast mitochondrial phosphate translocase.

Question 34

How does ML316 affect mitochondrial oxygen consumption?

Answer 34

Reduces mitochondrial oxygen consumption ## Footnote This is likely due to the inhibition of phosphate transport into the mitochondria.

Question 35

What functions does the phosphate translocase serve?

Answer 35

* Symporter for inorganic phosphate * Antiporter for protons ## Footnote It imports inorganic phosphate and protons into the mitochondrial matrix.

Question 36

Fill in the blank: The oxidation of NADH translocates _____ H⁺ out.

Answer 36

10 H⁺ ## Footnote This is part of the ATP synthesis process.

Question 37

Fill in the blank: The oxidation of FADH2 translocates _____ H⁺ out.

Answer 37

6 H⁺ ## Footnote This is relevant for calculating ATP yield from FADH2.