Macromolecule: giant molecules (many atoms, not just a few)  
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  

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

• Monosaccharides—just one saccharide group
  • Examples: glucose, fructose, galactose    
  • 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

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   

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

Cholesterol

• 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

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
  • Quaternary (optional) – combination of two or more tertiary proteins
• 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)
• Protein folding has become a vital part of our understanding of how proteins function in the body

Structural proteins

• Form structures, e.g. collagen, keratin

Functional proteins

• Act as “chemists” or “regulators”, e.g. hormones, neurotransmitters, enzymes
• Enzyme action
  • 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
      
  • Active site
  • Allosteric site (allosteric “shape changing” effect)
  • Cofactors help enzymes
    • Organic cofactors are coenzymes, e.g. vitamins
  • Enzymes are specific (only work with one type of substrate)

• Examples
  • • deoxyribonucleic acid (DNA)  
    • 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
      • 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
    • 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

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

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