Amino Acids and Proteins

How many standard amino acids are used to make proteins?

1. 20
2. 4
3. 10
4. 64

Which groups are attached to the central (alpha) carbon of an amino acid?

1. A sugar and a phosphate
2. A phosphate group and a base
3. Two amino groups and two carboxyl groups
4. An amino group, a carboxyl group, a hydrogen atom and an R group

Which is the simplest amino acid?

1. Lysine
2. Glycine
3. Alanine
4. Tryptophan

Why is glycine optically inactive?

1. It contains sulphur
2. It is a D-amino acid
3. Its alpha carbon is not chiral because its R group is hydrogen
4. It has no carboxyl group

A zwitterion is a molecule that:

1. Carries two positive charges
2. Carries no charge at all
3. Is a protein with four subunits
4. Carries both a positive and a negative charge

The isoelectric point of an amino acid is the pH at which:

1. It forms a peptide bond
2. It has no net charge
3. It denatures
4. It is fully positively charged

Which of these is an essential amino acid?

1. Leucine
2. Glycine
3. Serine
4. Alanine