Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

Living organisms contain proteins with an extremely broad range of sizes and shapes. Their roles are varied, and these roles depend on their structures. The structure and properties of a particular protein come from its primary structure - the amino acid sequence that makes up the protein.
(a(i))[2]

Proteins are known as condensation polymers. Write a balanced equation for the condensation reaction between two glycine molecules, $\text{H}_2\text{NCH}_2\text{CO}_2\text{H}$.

(a(ii))

Draw the skeletal formula of the organic product.

(b(i))[2]

X-ray analysis has revealed that many proteins contain sections with a regular arrangement within the polypeptide chain. This is called secondary structure and it occurs in two main forms. State the two forms of secondary structure found in proteins.

(b(ii))[2]

Draw a diagram to show one form of secondary structure.

(c)[4]

There are about 20 common amino acids in humans, and most of them share the same general structure:\n\n$\text{H}_2\text{NCH(R)CO}_2\text{H}$.\n\nThe identity of the $R$ group determines which bonds can form as the protein’s secondary structure folds further to produce tertiary structure. Complete the table to show the type of tertiary bonding that is likely to arise from each pair of amino acid residues.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Balanced equation: $\mathrm{2H_2NCH_2CO_2H \rightarrow H_2NCH_2CONHCH_2CO_2H + H_2O}$

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