One way of finding which amino acids are present in a polypeptide chain is electrophoresis. Draw and label the equipment used for electrophoresis.
During electrophoresis, different amino acids travel in different directions and at different rates. Which factors decide the direction in which an amino acid moves?
Which factors determine how fast an amino acid moves?
Another technique used to study protein structure is X-ray crystallography. It allows the positions of individual atoms to be found, along with the distances between them. Hydrogen atoms never form images in X-ray crystallography. Explain why this happens.
Suggest and explain which atom in a molecule of cysteine, $\text{H}_2\text{NCH(CH}_2\text{SH)CO}_2\text{H}$, would appear most clearly when X-ray crystallography is used.