Amino Acids

Question 1

What do all AA’s except proline have ?

Answer 1

an acidic carboxyl group , a basic amino group,

and an alpha-hydrogen connected to the alpha-carbon

Question 2

The fourth substituent (R) is unique – Why isn’t glycine chiral ?

Answer 2

In glycine, the fourth substituent is also

hydrogen.

Question 3

Glutamic acid and Aspartic acid Undergo some important reactions like what ?

Answer 3

Amination of R group, Ketone formation, and Removal carboxyl group from alpha carbon

Question 4

Facts about Uncommon Amino Acids in Proteins ?

Answer 4

• Not incorporated by ribosomes - except for Selenocysteine and Pyrrolysine
• Arise by post-translational modifications of proteins
• Reversible modifications, especially phosphorylation, are important in regulation and signaling

Question 5

Which type of AAs can be phosphorylated easily?

Answer 5

AAs with hydroxl groups

Question 6

What are peptides ?

Answer 6

Small condensation products of amino acids. (< 10kDA)

Question 7

What are some functions of peptides?

Answer 7

• Hormones and pheromones
• Neuropeptides
• Antibiotics
• Protection

Question 8

How many peptide bonds are in 5 AAs ?

Answer 8

4

Question 9

Which AAs have nonpolar, aliphatic R groups ?

Answer 9

Glycine, Alanine, Proline, Valine, Leucine, Isoleucine, Methionine.

Question 10

Which AAs have aromatic R groups ?

Answer 10

Phenylalanine, Tyrosine, Tryptophan

Question 11

Which AAs have polar, uncharged R groups ?

Answer 11

Serine, Threonine, Cysteine, Asparagine, Glutamine.

Question 12

Which AAs have positive R groups ?

Answer 12

Lysine, Arginine, Histidine

Question 13

Which AAs have negative R groups ?

Answer 13

Aspartate, Glutamate

Question 14

Two amino acids of the standard 20 contain

sulfur atoms. They are

Answer 14

Methionine and cysteine

Question 15

What’s special about cysteine ?

Answer 15

It can form disulfide bonds.