Amino Acid Structures: Primary

Question 1

What are amino acids linked by?

Answer 1

Peptide bonds

Question 2

How are peptide bonds formed?

Answer 2

1. condensation reaction/loss of water (dehydration)

2. carboxyl group of AA1 forms covalent bond with amino acids of AA2

Question 3

Start of the Peptide Bond

Answer 3

N-terminus (alpha amino group)

Question 4

End of the peptide bond

Answer 4

c-terminus (carboxylic acid group)

Question 5

What is the “Backbone?” for primary amino acids?

Answer 5

Repeated atoms in the

sequence: N-terminus, alpha carbon, c-terminus

Question 6

Are these peptide bonds planar?

Answer 6

planar (can’t rotate peptide bonds around each other)

Question 7

characteristics of peptide bonds

Answer 7

1. double bond characteristic
2. 1.32 angstroms
3. uncharged
4. 2 alpha carbon configurations (cis and trans)

Question 8

What is another way amino acids can be connected?

Answer 8

Disulfide bridges via cysteine residues

Question 9

How are disulfide bridges formed?

Answer 9

Oxidation reaction (oxidize sulfhydryl groups) to form covalent bonds

Question 10

How do you break disulfide bridges?

Answer 10

Using reducing agents to regenerate sulfhydryl groups

Question 11

What is a common reducing agent for breaking disulfide linkages?

Answer 11

β-mercaptoethanol

Question 12

List three different terms that distinguish lengths of peptides/proteins

Answer 12

1. Oligopeptide or simply “peptide”
2. Polypeptide
3. Protein

Question 13

What is the range of length for oligopeptides?

Answer 13

> 25 residues

Question 14

What is the range of length for polypeptides?

Answer 14

~25-50 residues

Question 15

What is the range of length for protein?

Answer 15

~50-2000 residues

Question 16

How long is one residue?

Answer 16

110 g/mol (110 Da) (i.e. protein

of 50 residues is 5500 g/mol (or 5.5 kDa))

Question 17

What does the primary sequence determine?

Answer 17

3-D structure of a

protein