1. Proteins
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 Structure: Elements: C, H, O, N monomer = amino acids
20 different
polymer = polypeptide
one or more polypeptide chains folded & bonded together
large & complex
complex 3-D shape
Rubisco = 16 polypeptide chains
Hemoglobin = 4 polypeptide chains (2 alpha, 2 beta)
hemoglobin
Rubisco
growth hormones

3. Amino acids H O | H || —C— C—OH —N— R Structure central carbon
amino group
carboxyl group (acid)
R group (side chain)
variable
different for each aa
Results in unique chemical properties
like 20 different letters of an alphabet
can make many words (proteins)
—N— H R

4. Effect of different R groups: Nonpolar amino acids
nonpolar & hydrophobic

5. Effect of different R groups: Polar amino acids
polar or charged & hydrophilic

6. Ionizing in cellular waters
H+ donors

7. Sulfur containing amino acids
Form disulfide bridges
covalent cross links betweens sulfhydryls
stabilizes 3-D structure
H-S – S-H
You wondered why perms smell like rotten eggs?

8. Building proteins dehydration synthesis Peptide bonds
covalent bond between NH2 (amine) of one aa & COOH (carboxyl) of another
C–N bond
H2O
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

9. 4 Classes of Protein Structure
1. Primary Structure – aa sequence determined by gene (DNA)
Phenylalanine
**slight change in sequence can affect protein’s structure & its function just one aa change can make all the difference!**

10. 2. Secondary Structure – folding due to interactions between adjacent (local) aa’s a. Alpha (α) Helix
b. Pleated Sheet

11. Secondary Structure of a Protein

12. 3. Tertiary Structure Overall primary and secondary structure
Hydrophobic interactions
H-bonds
Disulfide bridges
Ionic bonds between opposite charges

13. 4. Quarternary Structure – more than one polypeptide bonded together
**Increased complexity = increased stability!**

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

15. Conjugated Proteins Protein backbone with nonprotein group attached
Chromoprotein – pigment molecule attached Ex: Hemoglobin
“Glyco” & “Lipo”Proteins – in cell membrane; carb or lipid attached – used in cell identity
Nucleoproteins – proteins wrapped in DNA Ex: histones (in chromosomes)

16. The Many Functions of Proteins
Enzymatic
Structural
Transport
Receptor
Signalling
Defense
Movement (contractile)
Storage