Learning Outline

Biological Chemistry

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Pre-A&P (BIO 095)

Basic Structural Concepts

Macromolecule: giant molecules (many atoms, not just a few) slide
Polymer: macromolecule made up of many smaller molecules called “monomers”

  • Polymers are assembled by dehydration synthesis
  • Polymers are disassembled by hydrolysis

The major biological molecules we discuss in introductory human biology are:

  • carbohydrates, lipids (fats), proteins, and nucleic acids image

Carbohydrates

Saccharides (C6H12O6)—sugar groups that make up many carbohydrates

  • Monosaccharides—just one saccharide group
    • Examples: glucose, fructose, galactose image
    • Also called “simple sugars” or “single sugars”
  • Disaccharides—have two saccharide groups
    • Examples: sucrose, maltose, lactose
    • Also called “double sugars”
  • Polysaccharides—have many saccharide groups
    • Example: glycogen

Examples of function: fuel, fuel storage

Lipids

Triglycerides: three fatty acid “tails” and one glycerol holding them together

  • Nonpolar; hydrophobic
  • Fuel

Phospholipids: two fatty acid “tails” with a “head” containing glycerol and phosphate image

  • Tails are nonpolar; head is polar
  • Form bilayers in water
  • Form cellular membranes

Cholesterol image

  • Source of steroid lipids
    • For example, the body converts cholesterol into steroid hormones
  • Stabilizes phospholipid bilayers
    • Strengthens cellular membranes that are made up primarily of phospholipids

Proteins

Protein structure

Proteins are folded/twisted chains of amino acids

  • Proteins have 50 or more amino acids; polypeptides 10-50, peptides less than 10
    • These different categories are used very loosely in real life
  • Levels of protein structure (increasing degrees of structural complexity)
    • Primary – sequence of amino acids (determined by shape)
    • Secondary – folded (pleated sheets), twisted (helices) version of primary structure
    • Tertiary – folded and/or twisted version of secondary structure image
    • Quaternary (optional) – combination of two or more tertiary proteins image
  • Chaperone molecules assist proteins in folding properly
    • The proper (functioning) shape of a protein is called its “native state”
  • Denaturation is loss of proper 3D shape (native state)
    • May be caused by extreme temp, extreme pH, chemical reactions, other extreme conditions
    • Renatured proteins are those that have regained their native state after having been previously denatured
    • Chaperone molecules may assist in refolding denatured proteins
  • Misfolded proteins must be destroyed (and recycled) or they may cause damage
    • May form deadly plaque (gunk)
  • Categories of protein shape
    • Fibrous proteins
    • Globular proteins (globulus “small globe or sphere”)
      • Nearly any shape that isn’t “fibrous”
      • Also sometimes called globins
  • Structure of molecule determines function (it’s all about shape) slide
  • Protein folding has become a vital part of our understanding of how proteins function in the body

Types of Proteins

Structural proteins

    • Form structures, e.g. collagen, keratin

    Functional proteins

    • Act as “chemists” or “regulators”, e.g. hormones, neurotransmitters, enzymes
    • Enzyme action video
      • Lower “activation energy” of chemical reactions to body temp–that is, make chemistry happen that otherwise wouldn’t happen
      • Lock-and-key model
        • Enzyme fits substrate as a key fits into a lock
          lock and key
      • Active site
      • Allosteric site (allosteric “shape changing” effect) video
      • Cofactors help enzymes
        • Organic cofactors are coenzymes, e.g. vitamins
      • Enzymes are specific (only work with one type of substrate)

Nucleic acids

  • Examples
      • deoxyribonucleic acid (DNA) image
      • ribonucleic acid (RNA)
    • Encode genetic information
      • Structure/function of DNA discovered in 1953 by
        • James Watson
        • Francis Crick
        • Maurice Wilkins
        • Rosalind Franklin
    • Nucleotide is the subunit, made of three components
      • Sugar (ribose in RNA; deoxyribose in DNA)
      • Phosphate
      • Nitrogen base
        • Different types of nitrogen base
          • cytosine, guanine, adenine, thymine (DNA only), uracil (RNA only)
          • First letters are used as abbreviations: C, G, A, T, U cartoon
        • Bases may link C-G or G-C and T-A or A-T (in RNA, U-A or A-U)
          • This rule is complementary or obligatory “base-pairing”
    • RNA nucleotides link to form strands that sometimes fold
      • Some RNA types do form double strands
    • DNA nucleotides form a double strand that twists (double helix)
    • Information is encoded in the sequence of nitrogen bases
      • Every three bases is one codon or “word” in “genetish”
        • Each codon represents one amino acid in a sequence to form a protein
        • Genetish is what science author Matt Ridley calls the language of the genetic code
      • A gene is a sequence of codons that tells a cell the correct order of amino acids in a polypeptide (protein)
        • DNA is like a cookbook that contains recipes (genes) made up of words (codons) made up of different letters (nucleotide bases) that instruct the cell how to make a particular dish (specific protein)
    • ATP (adenosine triphosphate) is a modified nucleotide image
      • Breaking of last phosphate bond can release energy for cell work
      • [Very] temporary energy-storage “battery” of cell
      • Other modified nucleotides similarly transfer energy
        • NAD, FAD, CP
        • The role of each of these molecules will be discussed later in the course

Combined forms

  • Molecule made up of more than one type of macromolecule
    • Sometimes called “hybrid” molecules
  • Examples:
    • Glycoprotein
    • Proteoglycan
    • Glycolipid
    • Ribonucleoprotein
    • Lipoprotein

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Last updated: December 23, 2016 at 3:50 am