Agenda

  1. Turn in Lab 3 by the staplers on the North bench.
    1. Needs a name and group number
  2. ~10 min.: Q&A on Lab 3 material
  3. 20 min.: Quiz 3
  4. ~2 hrs.: Lab 4: Diffusion and Osmosis
  5. ~30 min.: Next lab reminders/questions/review

Lab 3 Q&A

What is an enzyme?

How does it work?

How do the following affect enzyme function?

  • Enzyme concentration
  • Substrate concentration
    • Saturation point
  • pH
  • Temperature

Catalase Function

2H_2O_2 \rightarrow 2H_2O + O_2
2H2O2→2H2O+O22H_2O_2 \rightarrow 2H_2O + O_2

Catalase

Catalase

  • Where is it found?
    • Peroxisomes, predominantly in the liver.
  • What does it do?
    • Degrades hydrogen peroxide to protect cells from oxidative stress.

Quiz 3

Diffusion & Osmosis

Lab 4

Lab Purpose

To allow students to experiment with osmotic forces and gradients and gain an appreciation for their effect on the human body on both the microscopic and macroscopic level.

Lab objectives

  • Define diffusion and be able to explain how it is affected by molecular size and temperature.
  • Given the concentration in grams/liter, moles/liter, or % solution, calculate the osmolarity of a solution.
  • Given the osmolarities on two sides of a selectively permeable membrane, calculate the osmotic pressure (π) in mmHg, and predict the direction of water flow.
  • Recall the normal osmolarity of human plasma and know what concentrations of NaCl and glucose are isotonic with plasma. Explain the effect of tonicity on red blood cells.

Lab Safety

  • Goggles!
  • Closed toed shoes
  • Gloves
  • Adequate coverage from neck to ankles
  • Put your hair up!
  • If you are exposed to someone else's blood TELL ME.
  • Permanganate solution goes in the bottle by the sink

Experiments

  • Solubility
  • Thistle tube osmometer
  • Mechanism for edema (dialysis sausage)
  • RBCs as a mini osmometer

Thistle Tube Osmometer Setup

Dialysis tubing "sausage"

RBC's as a mini osmometer

(and needle gun demo)

Core principles

What is diffusion?

  • How is it affected by:
    • Temperature
    • Molecule size

How to calculate osmolarity

Osmolarity = Molarity \times n
Osmolarity=Molarity×nOsmolarity = Molarity \times n

n is the number of particles the solute dissociates into when dissolved

\%\ solution = grams/100\ milliliters
% solution=grams/100 milliliters\%\ solution = grams/100\ milliliters

Know what % solution means

Osmotic Pressure

\pi = 19,300 mmHg \times \Delta C
π=19,300mmHg×ΔC\pi = 19,300 mmHg \times \Delta C
\Delta C = Osm_{solution_1} - Osm_{solution_2}
ΔC=Osmsolution1−Osmsolution2\Delta C = Osm_{solution_1} - Osm_{solution_2}

Normal Osmolarity of Human Plasma

  • 0.9% NaCl
  • 5.0% Glu

The Effect of Tonicity

We used 20% glucose today.

  • Hypertonic
  • Used clinically. Why?
  • When infused with hypertonic glucose, insulin is released to stimulate glucose uptake, reducing the concentration of glucose.

Lab 5: Action Potentials and Neurons

  • Read:
    • Stanfield pgs. 179-193
    • Silverthorn pgs. 240-254
  • Bring:
    • Goggles
    • Calculator
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