Respiration: The Link Reaction + Krebs Cycle S2

Question 1

When does the link reaction occur and where does it occur? When does the krebs cycle occur and where does it occur?

Answer 1

The link reaction is the second stage of aerobic respiration and the krebs cycle is the third stage of aerobic respiration. They both occur in the mitochondrial matrix

Question 2

How does the link reaction recieve the products of glycolysis? What are the products?

Answer 2

The link reaction recieves the products of glycolysis through active transport, from the cytoplasm to the mitochondrial matrix

Products: 2x pyruvate molecules
2x reduced NAD
2x ATP molecules

Question 3

Outline the stages of the link reaction:

Answer 3

1. Pyruvate is oxidised into acetate, resulting in the loss of a carbon dioxide molecule and two hydrogens
2. These hydrogens are accepted by NAD to form reduced NAD
3. Acetate combine switch co enzyme A to produced acetylcozenzyme A

Question 4

For every glucose molecule how many by times does the link reaction have to occur? What are the products of the link reaction after occurring?

Answer 4

The link reaction has to occur twice for every glucose molecule in order to form the products:

2 molecules of Acetylcoenzyme A
2 molecules of carbon dioxide released
2 molecules of reduced NAD

Question 5

What is the krebs cycle also known as?

Answer 5

The krebs cycle is known as the acid cycle

Question 6

Outline the krebs cycle:

Answer 6

1. The acetylcoenzyme A combined with a 4 carbon molecule to produce a 6 carbon molecule, releasing coenzyme A. The 6 carbon molecule is enters the Kreb cycle
2. In a series of redox reactions, the 6 carbon molecule loses a carbon dioxide and hydrogen to produce a 4 carbon molecule and a single molecule of ATP as a result of substrate level phosphorylation
3. The 4 carbon molecule now combines with acetylcoenzyme A to being the cycle again

Question 7

For each molecule of pyruvate, what does the link reaction and krebs cycle produce:

Answer 7

reduced coenzymes (NAD and FAD)
one molecule of ATP
three molecules of carbon dioxide

Question 8

What are coenzymes?

Answer 8

Coenzymes are not enzymes, but molecules SOME enzymes require to function

Question 9

What do coenzymes play a major role in?

Answer 9

They play a major role of carrying hydrogen atoms from one molecule to another

Question 10

What are some examples of coenzymes in respiration and photosynthesis? Why are they important in the chemical reactions they are involved in?

Answer 10

1. NAD = important throughout respiration
2. FAD = important in krebs cycle
3. NADP = important in photosynthesis