Energy Transfer

Question 1

Glycolysis

Answer 1

The breakdown of glucose into pyruvate

Question 2

Glycolysis Stage 1: Activation of Glucose by Phosphorylation

Answer 2

• Glucose is phosphorylated by 2 P(i) to increase its reactivity before it splits
• Inorganic phosphate comes from the hydrolysis of 2 ATP molecules
• 2ATP + 2H₂O –> 2ADP + 2P(i)
• Product of phosphorylation is glucose phosphate (unstable molecule)
• Activation of glucose lowers the activation energy for following reactions

Question 3

Glycolysis Stage 2: Phosphorylated Glucose Splits

Answer 3

Each glucose molecule splits into 2 triose phosphorylate (TP) molecules

Question 4

Glycolysis Stage 3: Oxidation of Triose Phosphate

Answer 4

• 1 Hydrogen is removed from each triose phosphate molecule
• The hydrogen is transferred to NAD (a hydrogen carrying molecule)
• The 2 NAD is reduced (each NAD molecule gains a hydrogen) and forms NADH

Question 5

Glycolysis Stage 4: Production of ATP

Answer 5

• Enzyme controlled reactions convert TP into 2 Pyruvate molecules (3 carbons)
• 2 ATPs are remade per 1 pyruvate molecule (4 ATPs made in total)
• Net gain of 2 ATPs (2 ATPs were used in stage 1, 4 were remade in stage 4)

Question 6

Glycolysis Summary (for a 4 marker)

Answer 6

• Phosphorylation of glucose using ATP
• Oxidation of triose phosphate (TP) to pyruvate
• NAD reduced
• Net gain of ATP (2 ATPs were used in stage 1, 4 were remade in stage 4)

Question 7

Yields of Glycolysis (Per Glucose Molecule)

Answer 7

• 2 pyruvate molecules
• Net gain of 2 ATP molecules (2 ATPs were used in stage 1, 4 were remade in stage 4)
• 2 NADH molecules (1 per TP molecule)

Question 8

Why is Glycolysis Indirect Evidence of Evolution?

Answer 8

• Glycolysis is a universal process that takes place in almost all living organisms
• Enzymes for this process are all located in the cytoplasm
• Glycolysis doesn’t require any organelles or membranes