Monday, 10/1
• Set up AP Lab #4: Diffusion & Osmosis
• Remember Lab Tuesday – Thursday
• Chp.6&7 TEST will be MONDAY!!!
Tuesday 10/2
• Lab 4 – start today
– Part A and Part B completed today
• Chp.6&7 Test will be MONDAY
• Lab continues tomorrow – dress
appropriately
• Set up a new page in your AP Bio Lab
Notebook
• Title: Lab 4 – Diffusion & Osmosis
• Subtitle 1st Section: Background Info
– Read background info, summarize in at least 2
paragraphs
– Include key words: diffusion, osmosis,
concentration gradient, hypertonic, isotonic,
hypotonic, solute concentration, plasma
membrane, cell wall, turgor pressure, water
potential, dynamic equilibrium, plasmolyze
2nd Section: Objectives
1. Growth, reproduction, and homeostasis require that cells
create & maintain internal environments that are different
from their external environments
2. Growth & homeostasis of a biological system are
influenced by changes in the system’s environment
3. Demonstrate diffusion across a semi-permeable
membrane
4. Measure the effects of various concentrations of solute on
the process of osmosis
5. Differentiate between hypotonic, isotonic, and hypertonic
environments
6. Measure and calculate water potential
7. Examine the effects of osmosis on plant cells
3rd section: Data
• Glue in Data Tables 1, 2 , & 3 and the
Plant Cell Plasmolysis data
4th section: Analysis/ Conclusion
Questions
• Glue in and create graphs
• You will be provided with these questions
at the end of the lab, glue in and answer in
this section
Safety
• Read all instructions before beginning lab.
• Wear PPE & apron.
• Wash hands before and after lab.
– Pores in dialysis tubing can easily be clogged
with oil & dirt from hands, keep contact to a
minimum
• IKI (potassium iodide) solution is an irritant,
can stain clothes, handle with care, and
wash off spills & splashes with water.
Procedure Overview –
Part A: Diffusion
• Fill dialysis tubing with glucose/starch soln.
• Test for glucose with glucose test strip.
– Positive is dark green/brown
• Place in beaker of distilled water with IKI
(potassium iodide) soln.
• Test soln. for glucose & record color.
• Wait 30 min, then record color and test for
glucose in dialysis bag and in beaker.
Procedure Overview –
Part B: Osmosis
• Fill 6 dialysis bags: water, 0.2M sucrose
soln, 0.4M, 0.6M, 0.8M, & 1.0M
• Blot dry, weigh each one, record initial
mass, and place in labeled cup
• Fill each cup with distilled water, wait 30
min.
• Remove, blot dry, weigh, record final mass
• Calculate percent change
• Graph data in analysis section
Procedure Overview –
Part C: Water Potential
• Get 4 potato cylinders (pre-cut)
• Weigh all 4 together & record initial mass
• Place into cup of 100mL of your assigned
solution, record temp, cover, wait
overnight
• Measure final temp, blot potatoes dry,
measure final mass
• Calculate % change & graph
Procedure Overview –
Part D: Water Potential Calculation
• Use provided formulas
• Record in conclusion question #9
Procedure Overview –
Part E: Plant Cell Plasmolysis
• Remove epidermal layer from onion
• Create wet mount & observe under
microscope 100x mag, record
observations
• Add 2-3 drops of 15% NaCl soln, wait 2-3
minutes, observe at 100x mag, record
observations
• Finish Lab Set-up
• Remember Lab Tomorrow – Thursday
• Chp.6&7 TEST will be MONDAY!!!