McMurry (kap.19,4)

Question 1

What are both peptides and proteins?

Answer 1

Amino acid polymers.

Question 2

what are individual amino acids called?

Answer 2

residues.

Question 3

What are residues joined together by?

Answer 3

amide bonds/peptide bonds.

Question 4

Depending on which carboxylic acid reacts with which amino group, there is formed different dipeptides .

See the example on page 690.

Answer 4

page 690.

Question 5

What is a protein backbone?

Answer 5

the continunuois chain of -N-CH-CO- is called the backbone.

Question 6

A peptide bond has a C-termin and a N-terminal.

Which is which, and what side should each be placed?

Answer 6

C-terminal (the one with the free carboxylic acid - placed on right side)

N-terminal (the one with the free amino group - placed on the left side).

Question 7

Why is a amin N basic but a amid N non-basic?

Answer 7

Because the amide N has its electrons delocalized by interactions with the carbonyl group.

The amide bond is therefore planar and the N-H is oriented 180 degrees to the C=O.

Question 8

The side chains is always alternating up/down. Why?

Answer 8

Because of the planar character of the peptide chain (because of the amide bonds).