1. Review

3. Review
Hydrophobic (non polar)
Hydrophilic (polar)

4. Polar Have a charge to them
Molecules with a positive and negative side
Non-symmetrical
Amino acids: amine, alcohol, amide functional group

6. Nonpolar No charge associated with a molecule
Electrons are evenly distributed creating no electrical field (charges cancel out each other)
Symmetrical shape
In amino acids (benzene ring/alkyl functional group)

8. Covalent bonds Share a pair of electrons
Both atoms are holding onto electrons
Stable –
H — H
H2 (hydrogen gas)

9. Nonpolar covalent bond
Pair of electrons shared equally by 2 atoms
Methane (CH4)

10. Polar covalent bonds Pair of electrons shared unequally by 2 atoms
Oxygen has higher electronegativity and will pull electrons more H
Oxygen + – – – – +

11. Polar or Non-polar C
POLAR A B
NONPOLAR
NONPOLAR D
POLAR

12. Amino acid

13. Hydrophobic R groups
Composed mostly of carbon and hydrogen, and tend to be repelled from water
Glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), phenylalanine (Phe), methionine (Met), and tryptophan (Trp).

14. Polar amino acids Side chains that are not charged
Serine (Ser), threonine (Thr), cysteine (Cys), asparagine (Asn), glutamine (Gln), and tyrosine (Tyr)

15. Basic amino acids Arginine (Arg), lysine (Lys), and histidine (His)
Their side chains contain nitrogen and resemble ammonia, which is a base

16. Acidic amino acids Acidic R groups
Aspartate (Asp) and glutamic acid or glutamate (Glu)

17. Bonds
Amino acids are linked together by peptide bonds

18. Primary (1°) structure Order of amino acids in chain
amino acid sequence determined by gene (DNA)
slight change in amino acid sequence can affect protein’s structure & its function
even just one amino acid change can make all the difference!
lysozyme: enzyme in tears & mucus that kills bacteria

19. Secondary (2°) structure
“Local folding”
folding along short sections of polypeptide
interactions between adjacent amino acids
H bonds
weak bonds between R groups
forms sections of 3-D structure
-helix
-pleated sheet

20. Tertiary (3°) structure
“Whole molecule folding”
interactions between distant amino acids
hydrophobic interactions
cytoplasm is water-based
nonpolar amino acids cluster away from water
H bonds & ionic bonds
disulfide bridges
covalent bonds between sulfurs in sulfhydryls (S–H)
anchors 3-D shape

21. Quaternary (4°) structure
More than one polypeptide chain bonded together
only then does polypeptide become functional protein
hydrophobic interactions
hemoglobin
collagen = skin & tendons

22. Protein structure (review)
R groups
hydrophobic interactions
disulfide bridges
(H & ionic bonds) 3°
multiple polypeptides
hydrophobic interactions 1°
amino acid sequence
peptide bonds 4° 2°
determined by DNA
R groups
H bonds

23. Protein denaturation Unfolding a protein
conditions that disrupt H bonds, ionic bonds, disulfide bridges
temperature pH
salinity
alter 2° & 3° structure
alter 3-D shape
destroys functionality
some proteins can return to their functional shape after denaturation, many cannot

24. Enzymes
Lock and key: The key (substrate) has a specific shape (arrangement of functional groups and other atoms) that allows it and no other key to fit into the lock (the enzyme).

25. Enzymes
Induced fit: The substrate is distorted (atoms are shifted, bonds are stretched, and reactive groups are brought close together).
Only molecules with the correct functional groups in the correct configurations are able to be induced to fit the active site of the enzyme.

26. Enzyme Inhibition