Chemistry 9701 · AS & A Level · Nitrogen compounds

Nitrogen compounds — practice question

Proteins in the human body are intricate polymers constructed from about 20 different amino acids. Alanine is a representative amino acid.
(a)[1]

Glycine, $\text{H}_2\text{NCH}_2\text{CO}_2\text{H}$, is the simplest amino acid and differs from every other $2$-amino acid in an important way. What is this difference?

(b(i))[2]

State one example of secondary structure and give the type of bonding that is responsible.

(b(ii))[4]

Give two examples of bonding that cause the tertiary structure, and give the amino acid responsible in each case.

(c)[1]

Suggest why globular proteins, such as enzymes, contain relatively small amounts of glycine and alanine compared with some other amino acids. You may wish to use the structures shown above.

(d(i))[2]

The two strands of the double helix are joined by hydrogen bonds between base pairs. What are the base pairs?

(d(ii))[3]

Protein-chain coding starts with $\text{AUG}$, and finishes with one of three 'stop' codes shown in the table. What amino acid sequence would be produced by the following bases? $\text{-AUGGGUAGCCUCGCAUCGUAA-}$

(d(iii))[5]

What effect would a mutation have on the amino acid sequence if the base at position $10$ in the series of bases above changed from $\text{C}$ to $\text{G}$?

Worked solution & mark scheme

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