Harvesting Electrons from the Cycle - Chapter 19

Question 1

How does the citric acid cycle start?

Answer 1

Condensation of acetyl-CoA with oxaloacetate to form citrate

Question 2

What does the citric acid cycle do to acetyl CoA?

Answer 2

Oxidizes the acetyl fragment to CO2, allowing high-energy electrons to be captured and carried by NADH and FADH2

Question 3

How many molecules of CO2 is released when acetyl-CoA is oxidized?

Answer 3

2

Question 4

In what form is energy captured as acetyl-CoA is oxidized?

Answer 4

NADH, FADH2, and ATP (or GTP)

Question 5

What happens in the first stage of the citric acid cycle?

Answer 5

An acetyl group (2 carbon compound) is condensed with oxaloacetate (a four-carbon compound) to produce citrate (a six-carbon compound)

Question 6

How many carbons in an acetyl group?

Answer 6

2

Question 7

How many carbons in oxaloacetate?

Answer 7

4

Question 8

How many carbons in citrate?

Answer 8

6

Question 9

What are the two stages of the citric acid cycle?

Answer 9

1. Introduction of carbons (Acetyl-CoA condensed with oxaloacetate to form citrate)
2. Regeneration of oxaloacetate via two decarboxylation reactions

Question 10

What kind of electron carriers are created by the Krebs cycle? What do they do?

Answer 10

3 NADH
1 FADH2

Ultimately, they reduce O2 in the electron transport chain, producing water and facilitating the pumping of protons across the mitochondrial membrane, creating an electrochemical gradient that drives ATP synthesis.

Question 11

How does oxidative phosphorylation work?

Answer 11

The electrons from NADH and FADH2
reduce molecular oxygen (O2) in the ETC, producing water. This electron transfer facilitates the pumping of protons across the mitochondrial membrane, creating an electrochemical gradient. This gradient drives ATP synthesis as protons flow back into
the mitochondrial matrix through ATP synthase.

Question 12

What is cellular respiration?

Answer 12

process by which cells generate energy from organic molecules; includes electron donors, electron acceptors, a connection to fermentation, and ATP generation

Question 13

What is the main electron acceptor?

Answer 13

O2 receives electrons from NADH and FADH2

Question 14

What happens to pyruvate in anaerobic conditions or cells without mitochondria?

Answer 14

Pyruvate from glycolysis undergoes fermentation. NAD+ is regenerated from NADH, allowing glycolysis to continue.

Question 15

What are the advantages to oxidation of acetyl CoA in the citric acid cycle?

Answer 15

1. Generation of 3 molecules of NADH, 1 molecule of FADH, and 1 molecule of ATP (or GTP)
2. Metabolic intermediates used serve as precursors to other biomolecules.
3. Intermediates can inhibit or stimulate the cycle, ensuring efficient energy production based on cellular demands.

Question 16

What does citrate synthase do?

Answer 16

Facilitates the condensation of acetyl CoA (2 carbons) with oxaloacetate (4 carbons) to produce citrate (6 carbons)

Question 17

What enzyme facilitates the oxidation of acetyl CoA?

Answer 17

citrate synthase