Ch 18: Amino Acids, Proteins, and Enzymes

1. Proteins are polymers of amino acids
   1. Example, Alcohol Dehydrogenase (an enzyme)
   2. Protein Functions Table
   3. Protein Functions Overview
2. Amino Acids
   1. Chiral zwitterions
   2. Side-Chain Groups
3. Peptide bonds are amide links (Proteins are "polypeptides")
   1. General bonding pattern: N-terminal to C-terminal
4. Protein Classification and Structure
   1. Fibrous vs. Globular Proteins
      1. Fibrous: fiber-like, insoluble in water. Example, keratin: in hair, outer skin layer
      2. Globular: many are somewhat spherical (not fiber-like), soluble in water. Example: chymotrypsin, a digestive enzyme
   2. Primary structure: the amino-acid sequence (e.g. ala-pro-ser-ser-gly-ala...)
   3. Secondary structure: specal fixed arrangements of the polypeptide backbone
      1. α-Helix and β-Sheet: hydrogen-bond patterns
      2. α-Helix and β-Sheet: ribbon drawings
   4. Tertiary structure: The overall 3D shape of single polypeptide: Amylase example
      1. Forces that maintain the structure
   5. Quaternary structure: The way multiple polypeptides are assembled (some proteins): Hemoglobin example.
5. Protein denaturation (unfolding)
6. Enzymes: biological catalysts (most are proteins)
   1. Catalyst definition: Any substance that increases the rate or speed of a chemical reaction without being changed or consumed in the reaction.
   2. Classes of Enzymes
   3. Enzyme Action: Lock and Key Model (Substrate Specificity)
   4. Enzyme Action: Induced Fit Model
   5. Some drugs are enzyme inhibitors
      1. Aciclovir (antiviral drug, reversible inhibition)
      2. Reversible inhibition diagram ("competitive")
      3. Irreversible inhibition, penicillin example
7. Enzyme Cofactors (some enzymes require non-protein cofactors to function)
   1. Inorganic cofactors are metal ions like zinc and copper ions
   2. Organic cofactors are called "coenzymes" and most are vitamins
      1. Vitamins are organic compounds that are essential in very small amounts for the maintenance of normal metabolism. They generally cannot be synthesized at adequate levels by the body and must be obtained from the diet.
      2. One example is the coenzyme, NAD, vitamin B₃ (niacin)