amino acids
Post on 03-Nov-2014
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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
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