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L6 Proteins Outline
63
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¨  Notes on
¨ 
¤ General
Properties
n Starch
n Cellulose
n Glycogen
L6: Proteins
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composed of C, H, O, N, and sometimes P and S
¨ generally quite large. A long polymer chain of
amino acid subunits linked end to end by a
peptide bond
¨ 
L6 Proteins
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Molecules composed of one or more chains of amino
acids
¨ Functions:
¤ Enzymatic: Guide almost all chemical reactions inside
the cell
¤ Structural:
n Elastin: gives skin its elasticity
n Keratin: makes up hair, horns, nails, scales and
feathers
¤ Transport: Hemoglobin moves oxygen
¨ 
L6: Proteins Overview
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Monomer
• Amino Acid
Polypeptide
• Several amino acids long
Protein
• Lots of amino acids
L6: Components of Proteins
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¨ 
1. Amino acids
¤ the building blocks of proteins
¤  while there are many a.a. in nature, only 20
are used in proteins
L6: Peptide Bond
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Dipeptide = a.a. — a.a.
L6 Protein Have 4 Levels of Structure
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1. Primary Structure (1°)
¤ 
¤ 
Has a linear shape
It is determined by the order of amino acids in the chain.
L6: Protein Have 4 Levels of Structure
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Secondary Structure (2°)
¤ The α-Helix:
n A spring like structure
¨ 
¤ β-
pleated sheet:
n Looks like a folded fan
L6 Protein Have 4 Levels of Structure
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Tertiary Structure (3°)
¨  Shape: Globular (“cupped
hand shaped”)
¤ Folding and twisting due to
hydrophobic and
hydrophilic parts joining
and repelling.
¨ 
L6 Protein Structure
4. Quaternary Structures
(4°)
¨  occurs when two or more
proteins are joined together
to form a protein complex.
¨  Held together by hydrogen
bonds or disulphide bridges
¨ 
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L6 Proteins:
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The function of proteins is directly linked to their 3D
structure.
¨ ***Form follows Function*** (vice versa)
¨ When a protein becomes altered because of
¨ 
¤  heat
Egg Demo
¤  acid
¤  chemicals
it becomes denatured and will no longer perform
its function.
¨ 
o p y!
!
ot C
83
Do N
21 Amino Acids
Do N
ot C
opy!
!
Cont.
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84
L6 8 Essential Amino Acids
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• phenylalanine
• valine
• threonine
• tryptophan
• isoleucine
• methionine
• leucine
• lysine
L6 Complete Proteins
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¨ 
• 
• 
• 
• 
• 
• 
• 
These foods contain all the essential amino acids
beef
chicken
fish
eggs
cottage cheese
soy
vegetables
L6 Proteins Assignment
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Read pgs 38-41
¨  Do 1-3 pg 41
¨