Glycolysis Intro

Question 1

Why is ATP energy rich?

Answer 1

• ATP is energy rich because of the presence of two phosphoanhydride bonds.
• A large amount of energy is liberated when ATP is hydrolysed to ADP + P_i or AMP + PP_i

Question 2

How does ATP drive metabolism?

Answer 2

• ATP drives metabolism by shifting the equilibrium of unfavourable reactions.
• Is vital for processes such as muscle contraction and respiration.

Question 3

TRUE or FALSE: ATP is turned over quickly in cells

Answer 3

TRUE

• ATP is turned over quickly in cells (<1 min) so we need to have a longer term storage of energy.
• Can turn over ~40kg per day (0.5kg/min in exercise).

Question 4

What is glycolysis?

Answer 4

A process that makes ATP in the absence of oxygen.

–Important in tissues with poor blood supply e.g. cornea or those with few/no mitochondria (kidney medulla / erythrocytes).

–Used to power a short sprint!

Question 5

Describe the properties of glycolysis

Answer 5

•Two stage process occurring in the cytoplasm:

1. Trapping and preparation (no ATP generated):

• Traps glucose in the cell.
• Cleaves glucose into 2 3C units

2. ATP harvesting:
   * 3C fragments are oxidised to pyruvate to go on to generate ATP

Question 6

Give an overview of glycolysis

Answer 6

1. Glucose is phosphorylated by Hexokinase to produce Glucose-6-phosphate
2. Phosphoglucose isomerase convers Glucose-6-phosphate→Fructose-6-phosphate
3. Fructose-6-phosphate is phosphoylated →Fructose 1,6-bisphosphate by phosphofructo kinase
4. Fructose bisphosphate aldose cleaves Fructose 1,6-bisphosphate→ Dihydroxyacetone phosphate + Glyceraldehyde-3-phosphate
5. Triose phosphate isomerase allows interconversion between these two moelcules- DHAP→GAP
6. Glyceraldehyde 3-phosphate dehydrogenase adds free inorganic phosphate in a redox reaction to produce 1,3-bisphosphoglycerate (GAP is oxidised and NAD+ is reduced to NADH)
7. Phosphoglycerate kinase phosphoylates ADP→ATP (thereby removing a phosphate from 1,3-bisphosphoglycerate to produce 3-Phosphoglycerate
8. Phosphoglycerate mutase rearranges 3-Phosphoglycerate to produce 2-phosphoylcerate
9. Enolase condenses 2-phosphoylcerate to produce Phosphoenolpyruvate (PEP)
10. Pyruvate kinase converts Phosphoenolpyruvate (PEP) to pyruvate by using the phosphate group from Phosphoenolpyruvate to convert ADP→ATP

Question 7

How many ATP moelcules do you get from glycolysis?

Answer 7

2