Transcript Amino Acids Proteins, and Enzymes

Amino Acids Proteins, and
Enzymes
Types of Proteins
Amino Acids
The Peptide Bond
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Types of Proteins
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Type
Structural
Contractile
Transport
Storage
Hormonal
Enzyme
Protection
Examples
tendons, cartilage, hair, nails
muscles
hemoglobin
milk
insulin, growth hormone
catalyzes reactions in cells
immune response
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Amino Acids
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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
H
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Examples of Amino Acids
H
I
H2N—C —COOH
I
H
glycine
CH3
I
H2N—C —COOH
I
H
alanine
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Types of Amino Acids
Nonpolar R = H, CH3, alkyl groups, aromatic
O
Polar
ll
R = –CH2OH, –CH2SH, –CH2C–NH2,
(polar groups with –O-, -SH, -N-)
Polar/Acidic
R = –CH2COOH, or -COOH
Polar/ Basic
R = –CH2CH2NH2
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Learning Check AA1
Identify each as (1) polar or (2) nonpolar
A. NH2–CH2–COOH
(Glycine)
CH3
|
CH–OH
|
B. NH2–CH–COOH
(Serine)
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Solution AA1
Identify each as (1) polar or (2) nonpolar
A.(2) NH2–CH2–COOH
(Glycine)
CH3
|
CH–OH
|
B. (1) NH2–CH–COOH
(Serine)
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Essential Amino Acids
• 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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Amino Acids as Acids and Bases
• Ionization of the –NH2 and the –COOH group
• Zwitterion has both a + and – charge
• Zwitterion is neutral overall
+
NH2–CH2–COOH
glycine
H3N–CH2–COO–
Zwitterion of glycine
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pH and ionization
OH–
H+
+
+
H3N–CH2–COOH
H3N–CH2–COO–
H2N–CH2–COO–
Positive ion
zwitterion
Negative ion
Low pH
neutral pH
High pH
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Learning Check AA2
CH3
CH3
+
H3N–CH–COOH
(1)
H2N–CH2–COO–
(2)
Select from the above structures
A. Alanine in base.
B. Alanine in acid.
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Solution AA2
CH3
CH3
+
H3N–CH–COOH
(1)
H2N–CH2–COO–
(2)
Select from the above structures
A. (2) Alanine in base.
B. (1) Alanine in acid.
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The Peptide Bond
Amide bond formed by the –COOH of an amino
acid and the –NH2 of the next amino acid
+
O
||
CH3
+ |
NH3–CH2–COH
O
+
||
H3N–CH–COO–
+
CH3
|
NH3–CH2–C – N–CH–COO–
|
H
peptide bond
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Peptides
• Amino acids linked by amide (peptide) bonds
Gly
H2Nend
Lys
Phe
Peptide bonds
Arg
Ser
-COOH
end
Glycyllysylphenylalanylarginylserine
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Learning Check AA3
What are the possible tripeptides formed
from one each of leucine, glycine, and
alanine?
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Solution AA3
Tripeptides possible from one each of
leucine, glycine, and alanine
Leu-Gly-Ala
Leu-Ala-Gly
Ala-Leu-Gly
Ala-Gly-Leu
Gly-Ala-Leu
Gly-Leu-Ala
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Learning Check AA4
Write the three-letter abbreviations for the
following tetrapeptide:
CH3
CH3
CH3 O
S
CH CH3
SH
CH2
CH O
CH2 O
CH2 O
H3N CH C N CH C N CH C N CH C O
H
H
H
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Solution AA4
CH3
CH3
CH3 O
S
CH CH3
SH
CH2
CH O
CH2 O
CH2 O
H3N CH C N CH C N CH C N CH C O
H
H
H
Ala-Leu-Cys-Met
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