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

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

IBDP Biology Paper 1 - All Chapters

Question

Which of these molecules is amphipathic?

▶️ Answer/Explanation
The molecule in option (A) has both hydrophilic and hydrophobic regions: a polar phosphate head group and nonpolar fatty acid tails. This dual nature makes it amphipathic, like a phospholipid found in cell membranes.
✅ Answer: (A)

Question

Lipids are more efficient energy stores than carbohydrates. What is a reason for this?

A. Lipids are bigger molecules than carbohydrates.
B. Lipids release more energy per gram than carbohydrates.
C. Lipids can be more easily mobilized than carbohydrates when needed.
D. Lipids can be used in aerobic and anaerobic respiration when needed.

▶️ Answer/Explanation

Answer: B. Lipids release more energy per gram than carbohydrates.

Explanation:

Lipids are more efficient energy stores because:

  • They contain more carbon–hydrogen (C–H) bonds than carbohydrates.
  • These bonds release more energy when broken during aerobic respiration.
  • Therefore, 1 gram of lipid provides more than twice the energy of 1 gram of carbohydrate.

This means the body can store more energy in less space using lipids, making them ideal for long-term energy storage, especially in animals.

Why the other options are wrong:

A. Lipids are bigger molecules than carbohydrates → Incorrect. Size does not determine energy yield per gram.

C. Lipids can be more easily mobilized than carbohydrates → Incorrect. Carbohydrates are actually faster to mobilize for quick energy, which is why the body uses glucose first.

D. Lipids can be used in aerobic and anaerobic respiration → Incorrect. Lipids can only be used in aerobic respiration. Anaerobic respiration relies exclusively on glucose.

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