Types of ProteinsAmino Acids

The Peptide Bond

1

Type Examples Structural tendons, cartilage, hair,

nails Contractile muscles Transport hemoglobin Storage milk Hormonal insulin, growth hormone Enzyme catalyzes reactions in

cells Protection immune response

2

Building blocks of proteins Carboxylic acid group Amino group Side group R gives unique

characteristics

R side chain I

H2H—C —COOH I

H3

H I

H2N—C —COOH I

H glycine

CH3 I

H2N—C —COOH I

H alanine4

Nonpolar R = H, CH3, alkyl groups, aromatic

OPolar ll

R = –CH2OH, –CH2SH, –CH2C–NH2,

(polar groups with –O-, -SH, -N-)Polar/Acidic

R = –CH2COOH, or -COOH

Polar/ BasicR = –CH2CH2NH2

5

Identify each as (1) polar or (2) nonpolar

A. NH2–CH2–COOH (Glycine)

CH3

| CH–OH

|

B. NH2–CH–COOH (Serine)6

Identify each as (1) polar or (2) nonpolar

A.(2) NH2–CH2–COOH (Glycine)

CH3

| CH–OH |

B. (1) NH2–CH–COOH (Serine)7

10 amino acids not synthesized by the body

arg, his, ile, leu, lys, met, phe, thr, trp, val

Must obtain from the diet All in diary products 1 or more missing in grains

and vegetables

8

Ionization of the –NH2 and the –COOH group

Zwitterion has both a + and – charge Zwitterion is neutral overall

+

NH2–CH2–COOH H3N–CH2–COO–

glycine Zwitterion of glycine

9

H+ OH–

+ +

H3N–CH2–COOH H3N–CH2–COO– H2N–CH2–

COO–

Positive ion zwitterion Negative ion

Low pH neutral pH High pH

10

CH3 CH3

+

H3N–CH–COOH H2N–CH2–COO–

(1) (2)

Select from the above structures

A. Alanine in base.

B. Alanine in acid.

11

CH3 CH3

+

H3N–CH–COOH H2N–CH2–COO–

(1) (2)

Select from the above structures

A. (2) Alanine in base.

B. (1) Alanine in acid.

12

Amide bond formed by the –COOH of an amino acid and the –NH2 of the next amino acid

O CH3

+ | | + |

NH3–CH2–COH + H3N–CH–COO–

O CH3

+ | | |

NH3–CH2–C – N–CH–COO–

| peptide bond H

13

Amino acids linked by amide (peptide) bonds

Gly Lys Phe Arg Ser

H2N- -COOH

end Peptide bonds end

Glycyllysylphenylalanylarginylserine14

What are the possible tripeptides formed from one each of leucine, glycine, and alanine?

15

Tripeptides possible from one each of leucine, glycine, and alanine

Leu-Gly-AlaLeu-Ala-GlyAla-Leu-GlyAla-Gly-LeuGly-Ala-LeuGly-Leu-Ala

16

Write the three-letter abbreviations for the following tetrapeptide:

17

H3N CH

CH3

C

O

N

H

CH C

O

N

H

CH C

O

N

H

CH C O-

OCH

CH CH3

CH3

CH2

SH

CH2

CH2

S

CH3

Ala-Leu-Cys-Met

18

H3N CH

CH3

C

O

N

H

CH C

O

N

H

CH C

O

N

H

CH C O-

OCH

CH CH3

CH3

CH2

SH

CH2

CH2

S

CH3