AP Bio chap 5 The Structure and Function of Large Biological Molecules

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Amino acid → peptide →polypeptide → protein

smaller → larger

Writing quiz 9/20 is about proteins

“Proteios” = first or primary

50% dry weight of cells, Contains: C, H, O, N, S

Protein Functions + examples, know 4/5

Enzymes (lactase) (most end in -ase)

Defense (antibodies)

Storage (milk protein = casein)

Transport (hemoglobin)

Hormones (insulin)

Receptors - Proteins are unable to cross cell membrane

Movement (motor proteins)

Structure (keratin)

Writing quiz 9/20 vvv

Four Levels of Protein Structure

1. Primary

   1. Amino acid (AA) sequence

   2. 20 different AA’s

   3. peptide bonds link AA’s

      R group = side chains

• Properties:

  • hydrophobic
  • hydrophilic
  • ionic (acids & bases)
  1. “amino” : -NH2
  2. “acid” : -COOH

Please tell us how a protein comes together

2. Secondary

   1. Gains 3-D shape (folds, coils) by H-bonding
   2. Alpha (α) helix, Beta (β) pleated sheet

   Basic Principles of Protein Folding

   1. Hydrophobic AA buried in interior of protein (hydrophobic interactions)
   2. Hydrophilic AA exposed on surface of protein (hydrogen bonds)
   3. Acidic + Basic AA form salt bridges (ionic bonds).
   4. Cysteines can form disulfide bonds.

3. Tertiary

   1. Bonding between side chains (R groups) of amino acids
   2. H bonds, ionic bonds, disulfide bridges, van der Waals interactions

4. Quaternary

   1. 2+ polypeptides bond together

9/20 primary structure to Quaternary structure

Chaperonins: assist in proper folding of proteins

Protein structure and function are sensitive to chemical and physical conditions

Unfolds or denatures if pH and temperature are not optimal

solidity (very salty) can denature

Can nature and denature naturally or can denature and never come back (faulty protein)

change in structure = change in function

Nucleic Acids - Function: store hereditary info

Nucleotide = Sugar + Phosphate + Nitrogen Base

Carbohydrates

• **__Fuel __**and building material
• Include simple sugars (fructose) and polymers (starch)
• Ratio of 1 carbon: 2 hydrogen: 1 oxygen or CH2O
• monosaccharide → disaccharide → polysaccharide
• Monosaccharides = monomers (eg. glucose, ribose)
• Polysaccharides:
  • Storage (plants-starch, animals-glycogen)
  • Structure (plant-cellulose, arthropod-chitin)
• Starch = α glucose monomers
• Cellulose = β glucose monomers

Lipids

1. Fats (triglyceride): store energy

   1. Glycerol + 3 Fatty Acids
   2. saturated, unsaturated, polyunsaturated

2. Steroids: cholesterol and hormones

3. Phospholipids: lipid bilayer of cell membrane

   1. hydrophilic head, hydrophobic tails

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