Transcript
Types of ProteinsAmino Acids
The Peptide Bond
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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
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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
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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
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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
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H+ OH–
+ +
H3N–CH2–COOH H3N–CH2–COO– H2N–CH2–
COO–
Positive ion zwitterion Negative ion
Low pH neutral pH High pH
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CH3 CH3
+
H3N–CH–COOH H2N–CH2–COO–
(1) (2)
Select from the above structures
A. Alanine in base.
B. Alanine in acid.
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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.
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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
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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?
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Tripeptides possible from one each of leucine, glycine, and alanine
Leu-Gly-AlaLeu-Ala-GlyAla-Leu-GlyAla-Gly-LeuGly-Ala-LeuGly-Leu-Ala
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Write the three-letter abbreviations for the following tetrapeptide:
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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
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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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