Ch 4: Molecules

Molecules

Monomers and Polymers

  • Monomers: small molecules that link together to form macromolecules, also known as polymers.
  • Polymers: chains of monomers.

Dehydration and Hydrolysis

  • Dehydration: a process where water is removed to create a new bond between molecules.
    • For water to form, a hydrogen ([H]) and a hydroxyl group ([OH]) must align.
  • Hydrolysis: a process where water is added to break a bond between molecules.
    • Dehydration links molecules together.
    • Hydrolysis breaks molecules apart.

Carbohydrates

  • Monosaccharide: monomers that make up sugars.
  • Carbohydrates: sugars that serve as a main source of energy for organisms (excluding plants).
    • Composed of carbon ([C]), hydrogen ([H]), and oxygen ([O]).
  • Disaccharide: two sugar monomers linked by dehydration.
    • Example: Maltose, formed from two glucose molecules via a 1-4 glycosidic linkage with the removal of a water molecule ([H_2O]).
  • Polysaccharide: long sugar chain linked by dehydration.
    • Examples: Starch, cellulose, and chitin.

Lipids

  • Lipids: fats mainly used for long-term energy storage.
    • Also function in cushioning and insulation.
    • Composed of carbon ([C]), hydrogen ([H]), and oxygen ([O]).
    • Hydrophobic: do not mix with water.
  • Saturated Fat: all carbon atoms have the maximum number of bonds (4), resulting in a linear structure.
  • Unsaturated Fat: some carbon atoms have double bonds, causing a bent structure.

Proteins

  • Proteins: perform various functions in a cell; coded for by DNA.
    • Composed of carbon ([C]), hydrogen ([H]), oxygen ([O]), and nitrogen ([N]); some contain sulfur ([S]).
  • Functions:
    • Grab molecules for cell communication.
    • Grab molecules to build or break polymers.
    • Act as channels or pumps for transporting substances in/out of the cell.
    • Structural components in hair, fur, horns, feathers, and skin.
    • Hormones for growth, development, metabolism, and reproduction.
    • Enable muscle contraction.
  • Amino Acids: monomers that make up proteins.
  • Polypeptide: another name for a protein.
  • Peptide Bond: bonds that hold amino acids together in proteins.

Protein Shape

  • Protein Shape: determines the specific job of the protein.
    • Controlled by four levels of folding.

Four Levels of Protein Folding

  1. Primary Structure:
    • The specific sequence of amino acids.
  2. Secondary Structure:
    • Coiling into alpha helices or folding into beta sheets, stabilized by hydrogen bonds.
  3. Tertiary Structure:
    • One part of the protein folds over to interact with another part of the same protein.
    • Hydrophobic portions fold inward, while hydrophilic portions fold outward.
    • Positive parts are near negative parts.
  4. Quaternary Structure:
    • Two or more different proteins attach to form one large protein.
    • Examples: Collagen and Hemoglobin.

Denaturing

  • Denaturing: a protein permanently unfolds, disrupting its function; it is not reversible.
    • Caused by:
      • Heat: increases protein motion, breaking bonds.
      • pH: breaks bonds.
        • Acids (pH less than 7) attract negative parts of proteins to [H^+] in the environment.
        • Bases (pH over 7) attract positive parts of proteins to [OH^-] in the environment.

Size Exclusion Chromatography

  • Separates molecules based on size using a resin bead column.
  • Larger molecules elute faster because they cannot enter the beads.
  • Smaller molecules elute slower because they can enter the beads.
  • Example:
    • Hemoglobin = 64,500 kiloDaltons
    • Vitamin B12 = 1,350 kiloDaltons

SDS PAGE

  • SDS PAGE: Sodium dodecyl-sulfate polyacrylamide gel electrophoresis.
  • Denatures proteins and separates them based on size using an electric field.