18.3 The Krebs cycle

Question 1

Outline the process during the kerbs cycle

Answer 1

1. Acetyl coenzyme A delivers acetyl group to Krebs Cycle
   Acetyl group (2 carbon) + Oxaloacetate (4 carbon) ⟶ Citrate (6 carbon)

2.Citrate undergoes decarboxylation & dehydrogenation ⟶ 5 carbon compound + CO2 + Reduced NAD

3.5 carbon compound undergoes further decarboxylation & dehydrogenation ⟶ regenerate oxaloacetate
Phosphorylates ADP, releases CO2 + reduced NAD

Question 2

How many products are produced during each turn of the Krebs cycle

Answer 2

3 Reduced NAD (NADH)
1 Reduced FAD (FADH2)
1 ATP (from substrate-level phosphorylation)

Question 3

What’s a coenzyme

Answer 3

molecule which transfers atom(s)

from 1 reaction to another

in a multi-step pathway

Question 4

What coenzymes are involved in the Krebs cycle

Answer 4

NAD + FAD + Coenzyme A

Question 5

What are the differences between NAD & FAD

Answer 5

NAD involved in all stages of cellular respiration, but FAD only involved in Krebs cycle
NAD accepts 1 hydrogen atom, but FAD accepts 2 to become reduced FAD
Reduced NAD oxidised at beginning of electron transport chain, reduced FAD is oxidised further along
Reduced NAD synthesises 3 ATP molecules, Reduced FAD synthesises only 2 ATP molecules

Question 6

What are coenzymes derived from

Answer 6

Vitamins

Question 7

How many carbon atoms does oxaloacetate contain

Answer 7

4

Question 8

How many carbon atoms does an acetyl group contain

Answer 8

2