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Practice · Biology · 2025 syllabus · B1.2

IB Biology B1.2 Proteins: practice questions

5 exam-style questions on B1.2 Proteins, SL and HL, 2 marked HL: 3 multiple choice, 1 short answer and 1 extended response. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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B1.2-01 · Paper 1A style · multiple choice · 1 mark

Amino acids in a vegan diet

Why do people following a vegan diet need to plan their protein intake carefully? [1]

  1. Plants cannot make some of the 20 amino acids, so plant proteins lack them.
  2. Some plant foods are low in certain essential amino acids, so varied sources are needed.
  3. Humans can synthesize all 20 amino acids, so dietary protein is not required.
  4. Non-essential amino acids can only be obtained from animal products.
Show the answer and the reasoning

Answer: B. B is correct. Essential amino acids cannot be synthesized in the body and must come from food, and a single plant food can be low in one or more of them, so combining sources (for example legumes with cereals) covers the full set. A is false: plants can synthesize all 20 amino acids and build their proteins from the same set as animals. C is false: the body can synthesize only the non-essential amino acids, which it makes from other amino acids. D reverses the definition: non-essential amino acids are exactly the ones the body can make for itself.

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The 5 questions in B1.2

  1. B1.2-01 Amino acids in a vegan dietPaper 1A style · multiple choice · 1 mark
  2. B1.2-02 Heat and enzyme shapePaper 1A style · multiple choice · 1 mark
  3. B1.2-03 pH and ionic bondsPaper 1A style · multiple choice · 1 mark · HL
  4. B1.2-04 Heat stability of enzymesPaper 2 style · short answer · 6 marks
  5. B1.2-05 Protein structure and functionPaper 2 style · extended response · 15 marks · HL

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.