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: Objectives1. 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!!!