Respiration

Question 1

What and where do the stages of aerobic respiration occur?

Answer 1

1. Glycolysis in cytosol
2. Link reaction in mitochondrial matrix
3. Krebs cycle in mitochondrial matrix
4. Oxidative phosphorylation (involving electron transport chain) in the inner mitochondrial membrane

Question 2

What are the main stages of glycolysis? (in order)

Answer 2

1. Phosphorylation of sugar
2. Lysis
3. Oxidation by dehydrogenation
4. Substrate level phosphorylation

Question 3

Describe stage 1 of glycolysis.

Answer 3

Stage 1: Phosphorylation of sugar

First, 2 phosphate groups are added to glucose to produce fructose 1,6-bisphosphate. (Phosphorylation)
The 2 phosphate groups are donated by 2 ATP molecules to phosphorylate the sugar, thereby forming 2 ADP molecules.
The phosphorylation step activates the sugar, making it more reactive and committing it to the glycolytic pathway.

Phosphorylation also confers a negative charge to glucose; hence, it cannot diffuse across the cell surface membrane, and it is trapped within the cytosol.

Question 4

Overall equation of glycolysis?

Answer 4

Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH

Question 5

[Glycolysis]

Answer 5

Hexokinase catalyses addition of the first phosphate to glucose. Phosphofructokinase (PFK)
catalyses addition of the 2nd phosphate to form fructose 1,6-bisphosphate.
* PFK is allosterically inhibited by excess ATP2

(in end-product inhibition) and/or citrate in

the cell.
* Conversely, PFK is stimulated by AMP and ADP (allosteric activators).
* Thus, rate of glycolysis is regulated according to the energy demands of the cells.