Home / IB DP Biology- B1.1 Carbohydrates and lipids – IB Style Questions For SL Paper 2

IB DP Biology- B1.1 Carbohydrates and lipids - IB Style Questions For SL Paper 2 - FA 2025

IBDP Biology Paper 2 - All Chapters

Question

The diagram illustrates the molecular structure of sucrose, a disaccharide that is broken down during digestion so the body can absorb the monosaccharides glucose and fructose.
(a) Name the reaction that splits a disaccharide into its monosaccharide components.
(b) Explain how the structure of capillaries enables efficient absorption of monosaccharides.
(c) Briefly describe how fructose can cross a cell membrane by facilitated diffusion.

Most-appropriate topic codes :

• TOPIC B1.1: Carbohydrates and lipids — part (a)
• TOPIC B3.2: Transport — part (b)
• TOPIC B2.1: Membranes and membrane transport — part (c)
▶️ Answer/Explanation
Detailed solution

(a)
The reaction is hydrolysis, a catabolic process that breaks chemical bonds using water.

(b)
Capillaries support nutrient exchange because:
• Their walls are only one cell thick, providing a very short diffusion distance.
• They create large surface areas through extensive branching networks.
• Many capillaries contain fenestrations (small openings) that allow molecules to move across more quickly.

(c)
Facilitated diffusion is passive and moves molecules down their concentration gradient. Fructose crosses the membrane using specific carrier or channel proteins that bind to it and help it pass through the phospholipid bilayer without requiring ATP.

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