Transcript Amino Acids Proteins, and Enzymes Types of Proteins Amino Acids

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
H2N—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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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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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
+
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H3N–CH–COO–
+
CH3
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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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Amino Acids, Proteins, and
Enzymes
Primary and Secondary Structure
Tertiary and Quaternary Structure
Protein Hydrolysis and Denaturation
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Primary Structure of Proteins
The particular sequence of amino acids
that is the backbone of a peptide chain or
protein
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
Ala-Leu-Cys-Met
H
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Secondary Structure – Alpha
Helix
• Three-dimensional arrangement of amino
acids with the polypeptide chain in a
corkscrew shape
• Held by H bonds between the H of –N-H group
and the –O of C=O of the fourth amino acid
along the chain
• Looks like a coiled “telephone cord”
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Secondary Structure – Beta
Pleated Sheet
• Polypeptide chains are
arranged side by side
• Hydrogen bonds form
between chains
• R groups of extend above and
below the sheet
• Typical of fibrous proteins
such as silk
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Secondary Structure – Triple
Helix
• Three polypeptide chains
woven together
• Glycine, proline, hydroxy
proline and hydroxylysine
• H bonding between –OH
groups gives a strong
structure
• Typical of collagen, connective
tissue, skin, tendons, and
cartilage
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Tertiary Structure
• Specific overall shape of a protein
• Cross links between R groups of amino
acids in chain
disulfide
–S–S–
+
ionic
–COO–
H3N–
H bonds
C=O
HO–
hydrophobic
–CH3 H3C–
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Globular and Fibrous Proteins
Globular proteins
“spherical” shape
Insulin
Hemoglobin
Enzymes
Antibodies
Fibrous proteins
long, thin fibers
Hair
Wool
Skin
Nails
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Quaternary Structure
• Proteins with two or more chains
• Example is hemoglobin
Carries oxygen in blood
Four polypeptide chains
Each chain has a heme group to
bind oxygen
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Protein Hydrolysis
• Break down of peptide bonds
• Requires acid or base, water and
heat
• Gives smaller peptides and
amino acids
• Similar to digestion of proteins
using enzymes
• Occurs in cells to provide amino
acids to synthesize other
proteins and tissues
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Hydrolysis of a Dipeptide
OH
CH3 O
CH2 O
+
H3N CH C N CH C OH
H2O, H
+
heat
H
OH
CH2 O
CH3 O
+
H3N CH COH
+
+
H3N CH C OH
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Denaturation
Disruption of secondary, tertiary and quaternary protein
structure by
heat/organics
Break apart H bonds and disrupt hydrophobic
attractions
acids/ bases
Break H bonds between polar R groups and
ionic bonds
heavy metal ions
React with S-S bonds to form solids
agitation
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Stretches chains until bonds break
Secondary Structure – Triple
Helix
• Three polypeptide chains
woven together
• Glycine, proline, hydroxy
proline and hydroxylysine
• H bonding between –OH
groups gives a strong
structure
• Typical of collagen, connective
tissue, skin, tendons, and
cartilage
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Applications of Denaturation
• Hard boiling an egg
• Wiping the skin with alcohol swab for
injection
• Cooking food to destroy E. coli.
• Heat used to cauterize blood vessels
• Autoclave sterilizes instruments
• Milk is heated to make yogurt
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Functions of Proteins
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Structure – collagen, keratin,elastin
Enzyme – lysozyme, amylase,
Transport – hemoglobin, lipoproteins
Contractile – actin, myosin, tubulin
Hormone – insulin, growth hormone
Antibody – IgG,
Pigment – melanin, rhodopsin
Recognition – CD4, MHC proteins
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