Lab Experiment

1
Lab Experiment 7

• Diffusion and Osmosis
• J. Ellen Lathrop-Davis

2
Transport Energy for Movement

• Active
• Requires ATP from cell
• Uses integral proteins to move materials against
  their concentration gradients ? cells only
• Passive
• no ATP required
• energy comes from Brownian motion substances
  move randomly with a NET movement from area of
  higher to area of lower concentration
• Concentration gradient
• Pressure gradient
• Temperature gradient

3
Cell Membrane

• Lipid bilayer
• Integral proteins
• Selectively permeable
• Hydrophobic (nonpolar lipids, O2, CO2) cross
• Hydrophilic (polar amino acids, carbohydrates,
  molecules and charged particles (ions)) do not
• Integral proteins
• Carrier proteins carry solutes across membrane
• Protein channels allow movement across membrane

4
Passive Transport

• Diffusion NET movement of substance from area
  of HIGH concentration to area of LOW
  concentration due to Brownian Motion
• Occurs in gases, liquids, semisolids, solids
• At EQUILIBRIUM movement continues, but is equal
  in all directions (no net movement no
  diffusion)
• Rate affected by
• Particle size and charge (larger moves more
  slowly)
• Size of gradient (higher gradient ? faster
  diffusion)

5
Osmosis

• Diffusion of water
• NET movement of water from area of HIGH water
  (low solute) concentration to area of LOW water
  (high solute) concentration across a membrane
• Solutions are recorded according to SOLUTE
  concentration

6
Solutions

• Isotonic solutions concentrations equal
• Will there be a NET movement of water? no
• Hypertonic solution has more solute
• Will there be a NET movement of water? yes
• Hypotonic solution has less solute
• Will there be a NET movement of water? yes

7
Osmosis Terms

• Hemolysis bursting of blood cells in hypotonic
  solution
• Crenation shrinkage of animal cells in
  hypertonic solution
• Plasmolysis shrinking of plant cells in
  hypertonic solution within cell walls (plasma
  membrane pulls away from cell wall)
• Turgid plant in hypotonic solution becomes
  stiff due to abundance of water within central
  vacuole
• Flaccid plant in hypertonic solution becomes
  limp due to loss of water within central vacuole
  (general shape remains the same due to presence
  of cell wall)

8
Experimental Methods

• Obtain 4 decalcified eggs, blot carefully to
  remove excess vinegar
• Place each egg into the weigh boat individually
  record the mass in Table 1 (p. 97) under Time 0
  min.
• Obtain 4 beakers and fill as follows
• 200 ml distilled water
• 200 ml 0.5 M glucose
• 200 ml 1.5 M glucose
• 200 ml 2.0 M glucose

9
Experimental Methods

• Obtain a 100-ml beaker of water and add a single
  crystal of potassium permanganate
• Observe the potassium permanganate in the beaker
• After 15 minutes take the eggs out and mass the
  eggs after drying them gently first. Dry the
  weigh boat between eggs.
• Observe changes in the beaker of potassium
  permanganate

10
Experimental Methods

• Repeat removing, drying and massing the eggs
  every 15 minutes for a total of 90 minutes
  record your data in Table 1.
• Determine percent change in egg mass
• (mass at new time) (initial mass) X 100
  change
• initial mass
• Record these data in Table 2
• Graph the percent-change data (Table 2)
• Observe changes in the beaker of potassium
  permanganate every 15 minutes

11
Short Lab Report

• Raw data for egg weights (Table 1)
• Calculated changes (Table 2)
• Graph of change over time for all 4 eggs
• Conclusions
• A.1.
• B.1.
• B.2.
• B.3.
• B.4

12
Conversion and Dosage Bonus

• Convert 25 mg/dl to g/ml
• A person needs 1.5 g of a medication available as
  500 mg tablets. How many tablets should she
  receive?