Home / IB DP Biology- C1.2 Cell respiration- IB Style Questions For HL Paper 2

IB DP Biology- C1.2 Cell respiration- IB Style Questions For HL Paper 2 -FA 2025

IBDP Biology HL Paper 2 -FA 2025- All Chapters

Question

During glycolysis, glucose is broken down into pyruvate as part of cellular respiration.
  glucose
     ↓
fructose 1,6-bisphosphate
     ↓
2 × triose phosphate
     ↓
  2 × pyruvate
(a) On the diagram, indicate:
(i) the point where P (phosphorylation) occurs;
(ii) the point where O (oxidation) occurs.
(b) Identify the part of the cell where glycolysis takes place.
(c) Explain how NAD becomes available again for glycolysis during anaerobic respiration in animal cells.

Most-appropriate topic codes (CED):

• TOPIC C1.2: Cell respiration — parts (a), (b), (c)
▶️ Answer/Explanation
Detailed solution

(a)

  glucose
     ↓   <-- (P)
fructose 1,6-bisphosphate
     ↓
2 × triose phosphate
     ↓   <-- (O)
  2 × pyruvate

(b)
Glycolysis occurs in the cytoplasm.

(c)
In anaerobic conditions, reduced NAD (NADH) donates its hydrogen to pyruvate, converting it into lactate. This process regenerates NAD⁺, allowing glycolysis to continue producing ATP even when oxygen is not available.

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