18.1 Glycolysis

Question 1

What is glycolysis?

Answer 1

first step of respiration

glucose broken down into pyruvate

releasing ATP (net 2) & NADH (2).

common to both aerobic & anaerobic.

Question 2

Outline the process of glycolysis:

Answer 2

1. Glucose + 2P_i ⟶ Hexose Bisphosphate (P_i from ATP destabilises glucose)
2. Hexose Bisphosphate ⟶ 2 Triose Phosphate (Unstable hexose bisphosphate breaks down into more stable TP)
3. 2(Triose phosphate + P_i ⟶ Triose Bisphosphate) (These P_i come from free P_i in cytoplasm rather than ATP)
4. 2(Triose Bisphosphate ⟶ Pyruvate + 2ATP + 2NADH)

• Oxidised by dehydrogenation
  
  • H + NAD ⟶ NADH
• Dephosphorylated, releasing 2 P_i each
  
  • P_i + ADP ⟶ ATP

Net 2 ATP, 2NADH, 2 Pyruvate, per glucose molecule

Question 3

What is the purpose of phosphorylation during glycolysis?

Answer 3

to destabilise the molecule

so that it undergoes lysis

Question 4

What are the net products of glycolysis?

Answer 4

2 ATP

2 NADH

2 pyruvate

Question 5

Why type of phosphorylation is glycolysis an example of?

Answer 5

substrate-level phosphorylation

Question 6

What is substrate-level phosphorylation?

Answer 6

formation of ATP

without involvement of electron transport chain

Question 7

Where do the phosphates come from during the phosphorylation of glucose during glycolysis?

Answer 7

ATP

Question 8

Where do the phosphates come from during the phosphorylation of triose phosphate during glycolysis?

Answer 8

free, inorganic phosphates from the cytoplasm

Question 9

Glycolysis

What is the difference in phosphates during the phosphorylation of triose phosphate compared to glucose?

Answer 9

phosphorylation of glucose: phosphate comes from ATP

phosphorylation of triose phosphate: free phosphates in cytoplasm are used

Question 10

What is the function of NAD in glycolysis?

Answer 10

to act as a coenzyme

Question 11

Explain how NAD acts as a coenzyme during glycolysis:

Answer 11

transfers atoms from 1 reaction to another in a multi-step pathway:

NAD accepts hydrogen atom from dehydrogenation of triose bisphosphate & is reduced

supplies hydrogen atom to enzyme involved in later stage of respiration

Question 12

Why may glycolysis occur in the cytoplasm as opposed to the mitochondrial matrix?

Answer 12

• enzymes required for glycolysis are present in cytoplasm not in mitochondrial matrix
• glucose too large to be transported into mitochondrion