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PROTEIN
FUNCTIONS OF PROTEINS
 The word 'protein' is derived from
a Greek word 'protas' meaning 'of
primary importance.‘
 High consumption of protein
(meat) is a symbol of civilization
itself (Max Rubner 1854-1932)
kwashiorkor
WHAT ARE PROTEINS
Protein Bozeman
PROTEINS
•Proteins are polymers of amino acids
chemically bonded to each other
•All proteins in humans are made up from 20
different amino acids
•Identification: many protein names end with –
in, -en, -ase
TYPES OF PROTEINS
1. Structural – collagen
Also Keratin for hair and nails
2. Contractile Proteins
Actin/Myosin in muscles)
Provide movement
muscle contraction
3. TRANSPORT PROTEIN
Cross Membrane Transport
membrane crossing
Oxygen Transport: Hemoglobin
4. STORAGE PROTEINS
Example: Casein
amino acid storage in mammalian milk (80% cow’s,
30% human milk)
5. PROTEIN HORMONES
Example: Insulin and Glucagon (blood sugar
regulation)
6. ENZYMES
Speed up reactions in the body
Example: Lactase breaks down Lactose into
Galactose and Glucose
How Enzymes work
7. IMMUNE PROTEINS
Defend body against pathogens
Example: Antibodies
Antibody function
Table 16.1 – page 534
Chapter 16.2
Amino Acids
SWBAT: know the structure of an amino acid and
be familiar with the classification of amino acids
ANATOMY OF AN AMINO ACID
AA are all the same
with regard to
1. Central carbon
2. Amino group
3. Carboxyl group
4. Extra Hydrogen
Differ with regard to
the R-side chain
ACID/BASE BEHAVIOR OF FUNCTIONAL GROUPS
At normal body pH (~7.4) the amino and carboxyl group exist in their charged version
+
NH3
amines are
bases:
accept a
proton H+
-
COO
carboxylic acids
are acids:
release a proton
H+
Called a Zwitterion: positively and negatively charged at the
same time!!!
AMINO ACID (R) GROUP
Side Chain (R)
Group can be:
1. Alkyl
2. Hydroxyl
3. Thiol
4. Amino
5. Carboxyl
6. Aromatic
7. Cyclical
8. Amide
Classification of Amino Acids
Polar
Amino Acid
Non-polar
Neutral
(not charged)
Charged
Positively charged
(Basic)
Negatively charged
(Acidic)
NONPOLAR AMINO ACIDS
R can be:
• Alkyl side chain
• Aromatic side chain
POLAR AMINO ACIDS
R can be:
• Hydroxyl (-OH)
• Thiol (-SH)
• Amide (-CONH2)
These can Hbond with water
ACIDIC AMINO ACIDS
R will be:
Carboxylic acid (-COOH)
Can ionize as
a weak acid
BASIC AMINO ACIDS
R group will contain:
an amino group that ionizes
as a weak base
AMINO ACID STEREOISOMERS
Amino acids (except Glycine) are
chiral – can exist as D or L
enantiomers
Fisher projections:
• Highest oxidized C on top: COOH
• R side chain at bottom
L - isomer – NH2 group on left
D - isomer – NH2 group on right
L-serine
D-serine
Only L-amino acids found in nature!