Proteins

1
Proteins the most incredible molecules of all
2
Jobs of Proteins

• Structural - collagen, elastin, keratin
• Storage egg albumin, milk casein, seed protein
• Transport hemoglobin membrane carriers
• Hormonal insulin
• Receptor on cell membranes, receive signals
• Contractile actin, myosin in muscle
• Defense antibodies immunoglobulin
• ENZYMES catalyze specific chemical reactions

3
Proteins are polymers of amino acids
Variable part
generalized structure
Carboxyl group
Central carbon
Amine group
There are 20 types of amino acids
emergent properties
4
The 20 amino acids of proteins nonpolar,
hydrophobic amino acidstend to cluster together
to help with tertiary structure
5
Figure 5.15 The 20 amino acids of proteins
polar and electrically chargedare hydrophilic
lie on outside of protein or help with tertiary
structure
Have acid or amino side groups that are ionized
6
Making a polypeptide chain
Dehydration synthesis
7
The primary structure of a protein
8
Secondary structure alpha helix and
beta sheet
9

• Alpha helices are
• rigid
• short in globular proteins and
• long in long,
• fibrous structural proteins like keratin,
  collagen

10
Examples of interactions contributing to the
tertiary structure of a protein
Sulfur containing amino acids like cysteine form
strong disulfide linkages
11
The quaternary structure of proteins
12
A single amino acid substitution in the
hemoglobin protein causes sickle-cell
diseasePrimary structure determines secondary
and tertiary structure shape.Shape determines
functionality
13
Figure 5.19x Sickled cells
14
Conformation of a protein, the enzyme lysozyme
Ribbon model
Atom model
15
Figure 5.24 Review the four levels of protein
structure
16
Figure 5.26 A chaperonin in actionChaperone
proteins guide folding of other proteins
17
Figure 5.25 Denaturation and renaturation of a
protein
Changes in pH and temp can denature proteins.
Renaturation Is not always possible
18
Figure 5.27 X-ray crystallography
19
Figure 5.21x Silk drawn from the spinnerets at
the rear of a spider
A very strong protein that man would like to
genetically engineer into some organism
20
Figure 5.21 Spider silk a structural protein