Amino acids and proteinsEdexcel International A Level Chemistry: Mind map

Exam questions on Amino acids and proteins

1. Alanine, CH₃CH(NH₂)COOH, is one of the amino acids found in proteins. A student dissolves alanine in water and then changes the pH of the solution by adding acid or alkali.
   Alanine (Mr = 89) is a solid with a high melting temperature, whereas butanoic acid (Mr = 88) is a liquid at room temperature. Suggest why.2 marks
2. Most amino acids found in proteins are chiral. A student has a solution of one pure enantiomer of alanine, CH₃CH(NH₂)COOH, and a solution of glycine, H₂NCH₂COOH, of the same concentration. Each is placed in turn in a polarimeter using monochromatic light.
   Explain why alanine shows optical isomerism.2 marks
3. Glycine, H₂NCH₂COOH, and alanine, CH₃CH(NH₂)COOH, can react together to form peptides.
   Give the structural formula of the dipeptide formed when the carboxylic acid group of glycine reacts with the amine group of alanine. Name the type of reaction and the small molecule released.3 marks