4.4 - Krebs Cycle

Question 1

What is the first step of the Krebs cycle?

Answer 1

2-C acetylcoenzyme A combined with 4-C molecule to create a 6-C molecule.

Question 2

What is the second step of the Krebs cycle?

Answer 2

6-C molecule loses 2XCO2. Also loses 2H to give a 4-C molecule. Single molecule of ATP produced via substrate-level phosphorylation. The 4-C molecule can now combine with a new molecule of acetyl CoA to start again.

Question 3

What’s the yield from the Link Reaction and Krebs?

Answer 3

Reduced coenzymes such as NAD and FAD.
One molecule of ATP.
3XCO2.

Question 4

What happens to the hydrogen lost during the Krebs cycle?

Answer 4

It is accepted by NAD and FAD to create reduced NAD and reduced FAD respectively.

Question 5

What is the definition of a coenzyme?

Answer 5

Molecules that some enzymes require in order to function.

Question 6

When is NAD important?

Answer 6

Throughout respiration;.

Question 7

When is FAD important?

Answer 7

Krebs cycle.

Question 8

When is NADP important?

Answer 8

Photosynthesis.

Question 9

Why is the Krebs cycle important? (4 reasons)

Answer 9

1. ) Breaks down macromolecules into smaller ones (e.g. pyruvate -> CO2).
2. ) Produces Hydrogen atoms carried by NAD to ETC for oxidative phosphorylation. Leads to production of ATP.
3. ) Regenerates 4-C molecule. Would otherwise accumulate.
4. ) Source of intermediate compounds used by cells in manufacture of other important substances, (e.g. fatty acids, amino acids, chlorophyll).

Question 10

Where does the Krebs cycle take place?

Answer 10

Matrix of the mitochondria.