1. Multipurpose molecules
Proteins
Multipurpose molecules
clockwise:
Rubisco — most important protein on the planet?
Hemoglobin — a red blooded protein :-)
Collagen — strings you together
Growth Hormones — working hard in you right now!

2. Proteins
Most structurally & functionally diverse group of biomolecules
Function:
involved in almost everything
enzymes (pepsin, polymerase, etc.)
structure (keratin, collagen)
carriers & transport (membrane channels)
receptors & binding (defense: antibodies)
contraction (actin & myosin)
signaling (hormones: insulin)
storage (bean seed proteins)
Storage: beans (seed proteins)
Movement: muscle fibers
Cell surface proteins: labels that ID cell as self vs. foreign
Antibodies: recognize the labels
ENZYMES!!!!

3. Proteins Structure: monomer = amino acids polymer = polypeptide
20 different amino acids
polymer = polypeptide
protein can be one or more polypeptide chains folded & bonded together
complex 3-D shape
hemoglobin
Rubisco
growth hormones

4. In Biology, size doesn’t matter,
Denature a protein
In Biology, size doesn’t matter,
SHAPE matters!
Unfolding a protein
disrupt 3° structure
pH  salt  temperature
unravels or denatures protein
disrupts H bonds, ionic bonds & disulfide bridges
destroys functionality
Some proteins can return to their functional shape after denaturation, many cannot
Example:
Eggs:
Cooking an egg permanently denatures the proteins.

5. Amino acids H O | H || —C— C—OH —N— R Structure: central carbon
amino group
carboxyl group (acid)
R group (side chain)
variable group
confers unique chemical properties of the amino acid |
—C— H
C—OH || O
—N— H R

6. Why are these nonpolar & hydrophobic?
Nonpolar amino acids
nonpolar & hydrophobic
Why are these nonpolar & hydrophobic?

7. Why are these polar & hydrophillic?
Polar amino acids
Polar/charged & hydrophilic
Why are these polar & hydrophillic?

8. Sulfur containing amino acids
Form disulfide bridges
cross links betweens sulfurs in amino acids
H-S – S-H

9. dehydration synthesis
Building proteins
Peptide bonds
linking NH2 of one amino acid to COOH of another
C–N bond
dehydration synthesis
free COOH group on one end is ready to form another peptide bond so they “grow” in one direction from N-terminal to C-terminal
peptide bond

10. Building proteins Polypeptide chains N-terminus = NH2 end
C-terminus = COOH end
repeated sequence (N-C-C) is the polypeptide backbone
can only grow in one direction

11. Primary (1°) structure Order of amino acids in chain
determined by gene (DNA)
sequence can affect protein’s structure & function
Sickle cell anemia: 1 DNA letter changes 1 amino acid = serious disease
Hemoglobin mutation: bends red blood cells out of shape & they clog your veins.
lysozyme: enzyme in tears & mucus that kills bacteria

12. Secondary (2°) structure
“Local folding”
interaction between adjacent amino acids
H bonds between R groups
-helix
-pleated sheet
It’s a helix or B sheet within a single region. Can have both in one protein but a specific region is one or another

13. Tertiary (3°) structure
“Whole molecule folding”
determined by interactions between R groups
hydrophobic interactions
water in cell
anchored by disulfide bridges (H & ionic bonds)
How the whole thing holds together

14. Quaternary (4°) structure
More than one polypeptide chain joined together
only then is it a functional protein
Structure equals function wonderfully illustrated by proteins
Collagen is just like rope -- enables your skin to be strong and flexible.
hemoglobin
collagen = skin & tendons

15. Protein structure (review)
R groups hydrophobic interactions,
disulfide bridges 3°
multiple polypeptides
hydrophobic interactions
sequence determines structure and…
structure determines function.
Change the sequence & that changes the structure which changes the function. 1°
aa sequence
peptide bonds 2°
determined by DNA
R groups
H bonds 4°