Overview
Outline of lab report requirements (as much as you can, start with information from textbook and lecture):
I. Introduction:
A. Diffusion and osmosis
i. Define diffusion and osmosis
ii. Where is diffusion and osmosis are use in the human body:
1. Hydrophobic substances entering via plasma membrane: fatty acids, O2
and CO2
2. Ions entering via channels
3. Water passing through aquaporin channels (osmosis)
4. Neurotransmitters passing through synaptic clefts
iii. What distances are passed in each of the cases in “b” above:
1. Plasma membrane thickness is about 0.004 um
2. Channels are a little over 0.004 um → ~6 um?
3. Aquaporin channels also ~ 0.006 um
4. Synaptic cleft is around 0.02 um
iv. Therefore, we are interested in diffusion over a very short distance
B. Reaction time: It starts with transduction in the eye and goes through upwards of 10 cells and nerves and 10 synapses with thousands if not millions of ion channels (Na+ and K+ for action potentials) and Ca2+ (for neurotransmitter release)
C. Therefore, we need to map out the anatomical pathway for reaction time
D. Hypothesis is that watching and calculating the speed of diffusion of food dye over short distance will give us a sense of how fast things happen in the steps needed to complete our reaction time which rely on diffusion through synaptic clefts for neurotransmitters and via Na+ and K+ channels for action potentials and Ca2+ channels for
neurotransmitter release.
II. Materials and Methods:
A. Based on food dye experiment demonstration
B. Based on reaction time experiment demonstration
III. Results:
What data did we get for:
A. Diffusion rate over short distance
B. Reaction time
IV. Discussion
A. Look at the food dye rate of diffusion in um/sec
B. Look at your reaction time in um/sec
C. Map out your reaction time pathway
D. Think about adding the rate of diffusion in um/sec for millions of ~0.006 um distances for channels and tens of ~0.02 um distances for synaptic clefts
E. Do your calculations in “D” give a fast enough diffusion for how fast the reaction time is? If so, then your hypothesis is proven correct. If no, then the hypothesis is proven incorrect.
V. Conclusions
Summarize what you learned in this lab.