BSCI 230: Lecture 2: 1 February 2001

Lecture #1 Summary:

  •     Get Lab manual and review syllabus
  •     Properties of Prokaryotes and Eukaryotes
  •     Cell organelle functions
  •     Factors restricting cell size
  •     Surface area to volume ratio
  •     Diffusion distance
  •     Intracellular solute concentration


    • Five Important Principles from Chapter 2

  •     Why Carbon?
  •     What's so special about water?
  •     Selective permeability
  •     Polymerization of small molecules
  •     Self assembly of macromolecules


    • Why Carbon?

  •     Versatile structure due to 4 unpaired outer shell electrons - 4 bonds
  •     Easily forms bonds with H, O, and N
  •     Bonds form at different angles for molecules of different shapes
  •     See Figures 2-2 and 2-3 for energetic considerations


    • Why Carbon?
    Adding O and/or N gives us functional groups:
    -OH - Hydroxyl
    CH3 - Methyl
    NH2 - Amino
    see Figure 2-5 and know these groups!
    Water
     
     

    Properties of Water

    Hydrogen bonds (polar interactions as opposite charges attract) hold it together
    Water molecules are cohesive

  •     It's a liquid at most surface temperatures on Earth
  •     Surface tension and capillary action
  •     Properties of Water
  •     High boiling point (high specific heat)
  •     High heat of vaporization
  •     Good solvent for other polar molecules
  •     Forces nonpolar molecules to adhere together in an organized structure
  •     @ 4oC it is most dense so it freezes from top down
  •     It ionizes


    • Ionization of Water
    H2O <----> H+ + OH-

    In pure water, [H+ ] = [OH-]
    [H+] in solution
    [H+] in pure water =0.0000001M
    or 10-7 moles/liter

    so: Log10 [H+ ] = -7

    and: - Log10 [H+ ] = 7
    [H+ ] or pH
    pH is a way to express the [H+ ]
    pH = -Log10 [H+ ]
    Ionization of Water
    H2O <----> H+ + OH-

    Add a base, [H+] decreases and pH increases
    Add an acid, [H+] increases and pH decreases

    pH Quiz
    If [H+ ] = 0.001 M, pH = ????
        = 3

    If [H+ ] = 10-5 M, pH = ???
        = 5

    If Log of [H+ ] = - 10, pH = ????
        = 10

    pH of Various Solutions

  •     Stomach acid = pH of 1
  •     Coca Cola = pH of 3
  •     Water = pH of 7
  •     Baking soda = pH of 9
  •     Oven cleaner = pH of 13
  •     Drain cleaner = pH of 15


    • Why is pH (i.e., [H+ ]) Important?

    Principle #3:
    Selective Permeability:

    Determined by the physical properties of the molecular components of the cell membrane
    Phospholipid structure from text

    Drawing a lipid: ball abd stick figure

    Floating Lipids on Water?
    Lipids mixed in water:
    Micelle:
    Lipids in water:
    Bilayer:
    Cell Plasma Membranes Contain Lipids in Bilayers

    What does the structure of a lipid bilayer tell us about its permeability?
    Selective for non-polar, lipid soluble molecules
    How does a cell allow specific polar solutes to cross the bilayer?
    Specific channels or transport sites inserted into the membrane

    Principle 4: Polymerization

    Most often by dehydration synthesis
    Storage of monomeric units
    Structural molecules
    Informational molecules
     

    Self Assembly
    Structure or shape of macromolecule is determined by the components

    Higgins Rule #4:
    Molecular components determine macromolecular shape and shape determines function. Change the shape and the function changes.

    Carbohydrates

    Basic structure:
    Carbohydrates
    Simple sugars or monosaccharides

    Number of carbons
    5 C = pentose
    6 C = hexose
    Polar - why?
    Solubility & Permeability?

    Glucose - a hexose
    Fructose - a hexose
    Glucose in Solution be able to draw this figure (see text)

    Dehydration Reaction - linking monomeres into polymeres - Polymerization

    Linkages
    Bottom to bottom is an alpha linkage: ?
    Bottom to Top is a Beta linkage: ?

    Many monosaccharides linked together gives us polysaccharides

    Possible Linkages: Glycogen

    Glycogen vs. Cellulose
    Glycogen has ??1-4 and 1-6 linkages
    Cellulose has ? linkages
    this means every other glucose unit is ëupside downí when compared to glycogen
     
     

    Amino Acids and Proteins

    Amino Acid Structure: be able to draw generic amino acid!!!
     
     

    Amino Acids (Fig 3.2)
    R may be

  •     non-polar,
  •     polar ( + or - ),
  •     or ionic (COO- or NH3+)


    • Amino Acids

    You will be expected to examine an amino acid and determine whether the R group is polar, non-polar, or ionic.

    See Figure 3-2