BIOLOGY PAPER 3

Chapter 3 – Movement of Substances across the Plasma Membrane

List of PEKA experiments:

1. The movement of substances across a semi-permeable membrane
2. To demonstrate the process of osmosis using simple osmometer
3. Conducting a role-play to show the movement of substances across the plasma membrane
4. Studying the effects of hypotonic, hypertonic and isotonic solutions on animal cells
5. To study the effects of hypotonic, hypertonic and isotonic solutions on plant cells (cell sap of onion cells)
6. Determining the concentration of an external solution which is isotonic to the cell sap of a plant

Number	Activity 3.1 (Experiment)
Pg.	20
Title	The movement of substances across a semi-permeable membrane
Aim / Objective of the Study	To study the movement of substances across the Visking tubing
Problem Statement	What factor influences the diffusion of substances through a semi-permeable membrane?
Hypothesis	The diffusion of molecules through a semi-permeable membrane is based on the size of the molecule
Variables	Manipulated variable: Size of the solute molecules in the Visking tubing Responding variable: Colour of the solution in Visking tubing Fixed variable: Time, volume of solutions and surrounding temperature
Material	Benedict’s solution 1% starch suspension Iodine solution 30% glucose solution Distilled water
Apparatus	Visking tubing Cotton thread Test tubes Beakers Water bath (Bunsen burner, tripod stand & wire gauze)
Technique used	Test for the presence of starch and glucose with iodine and Benedict’s solution respectively

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Number	Activity 3.2 (Experiment)
Pg.	23
Title	Studying osmosis using an osmometer
Aim / Objective of the Study	To demonstrate the process of osmosis using simple osmometer
Problem Statement	What substances can diffuse through a semi-permeable membrane?
Hypothesis	Osmosis takes place when water moves from a region of low solute concentration to a region of high solute soncentration across a semi-permeable membrane
Variables	Manipulated variable: Concentration of solution Responding variable: Increase in the level of sucrose solution / The level of sucrose solution in the capillary tube Fixed variable: Concentration of sucrose solution, surrounding temperature
Material	30% sucrose solution Distilled water
Apparatus	25 cm capillary tube Visking tubing Retort stand and clamp Cotton thread Ruler Marker pen A pair of scissors 250 ml beaker Syringe Stopwatch
Technique used	Measure and record the increase in the height of sucrose solution with a ruler.

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Number	Activity 3.3 (Simulation)
Pg.	26
Title	Conducting a role-play to show the movement of substances across the plasma membrane
Aim / Objective of the Study	To study the movement of soluble substances across the plasma membrane through the process of passive transport. To study the movement of water molecules across the plasma membrane by osmosis To study the movement of substances across the plasma across the plasma membrane through the process of active transport.
Material	Strings Cardboard A pair of scissors Marker pen
Apparatus	-
Technique used	Conduct an interesting and creative role-play to learn the movement of substances across the plasma membrane (phospholipid bilayer)

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Number	Activity 3.4 (Observation)
Pg.	27
Title	Studying the effects of hypotonic, hypertonic and isotonic solutions on animal cells
Aim / Objective of the Study	To study the effects of hypotonic, hypertonic and isotonic solutions on animal cells (red blood cells)
Material	Fresh chicken blood 0.15 M sodium chloride solutions 0.50 M sodium chloride solutions Distilled water Filter paper
Apparatus	Glass slides Cover slips Filter papers Light microscope Test tubes Beakers Dropper
Technique used	Observe and study the effects of hypotonic, hypertonic and isotonic solutions on animal cells from the slides by using microscope

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Number	Activity 3.5 (Observation)
Pg.	28
Title	Studying the effects of hypotonic, hypertonic and isotonic solutions on plant cells
Aim / Objective of the Study	To study the effects of hypotonic, hypertonic and isotonic solutions on plant cells (cell sap of onion cells)
Material	Onion bulb 0.5 M sucrose solutions 1.0 M sucrose solutions Distilled water
Apparatus	Light microscope Glass slides Cover slips Razor blade / scalpel A pair of forceps Mounting needle Filter papers
Technique used	Observe and study the effects of hypotonic, hypertonic and isotonic solutions on plant cells from the slides by using microscope.

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Number	Activity 3.6 (Experiment)
Pg.	30
Title	Determining the concentration of an external solution which is isotonic to the cell sap of a plant
Aim / Objective of the Study	To determine the concentration of an external solution which is isotonic to the cell sap of a plant
Problem Statement	What is the concentration of an external (sucrose) solution which is isotonic to the cell sap of plants?
Hypothesis	The concentration of the solution which is isotonic to the cell sap of plant cells has no effect on the mass, length and size of plant cells. 0.36 M sucrose solution is isotonic to the cell sap of plants
Variables	Manipulated variable: Concentration of sucrose solution Responding variable: Length of potato strips / Mass of potato strips Fixed variable: Volume of sucrose solution used, surrounding temperature and time
Material	Fresh potato Distilled water 0.1 M sucrose solution 0.2 M sucrose solution 0.3 M sucrose solution 0.4 M sucrose solution 0.5 M sucrose solution 0.6 M sucrose solution
Apparatus	Petri dishes A pair of forceps Razor blade / Sharp scalpel Cork borer Ruler 50 ml beakers Electronic scale / electronic balance Tissue paper
Technique used	Measure the length of potato strips with ruler Determine the percentage difference in length Mass of potato strips with an electronic balance Determine the percentage difference in mass