IB Biology HL B1.2 Proteins questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

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Question 1

Multiple choiceEasy1 mark

A student is considering possible polypeptides assembled from the 20 amino acids represented in the genetic code. Which statements describe the possible chains?

I. Two chains can contain the same amino-acid types in different orders.
II. Each chain must contain all 20 amino-acid types.
III. Chains can range in length from a few amino acids to thousands.

Show answer and explanation

Answer: C. The 20 amino-acid types are possible building blocks, but their order and the length of a polypeptide chain can vary. Thus I and III are correct; a chain need not contain every type.

A: accepts variation in order but incorrectly assumes chain length cannot vary.
B: accepts variation in length but assumes amino-acid order is fixed.
D: mistakes the 20 amino acids available for a set that every chain must contain.

Remember: a polypeptide can use a subset of the 20 amino-acid types in different orders and chain lengths.

Question 2

Paper 2Easy2 marks

A researcher compares two proteins that contain the same types of amino acids but in a different order.

(a)

Explain why the proteins may have different three-dimensional conformations.

[1]
(b)

State the role of hydrogen bonds in stabilizing alpha helices and beta-pleated sheets.

[1]

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