2. 4.1 Fluid Mosaic Membranes
a. Describe and Explain the fluid mosaic model of membrane structure.
b. Outline the roles of cell surface membranes.
c. Outline the process of cell signaling.
4.2 Movement of substances into and out of cells
a. Describe and Explain the processes of diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and exocytosis.
b. Investigate diffusion and osmosis using plant tissue and nonliving materials, such as
Visking tubing and agar
c. Calculate surface areas and volumes of simple shapes (including cubes).
d. Investigate the effect of changing surface area to volume ratio on diffusion using
agar blocks of different sizes
e. Investigate the effects of immersing plant tissues in solutions of different water
potentials, using the results to estimate the water potential of the tissues
f. Explain the movement of water between cells and solutions with different water
potentials and explain the different effects on plant and animal cells
9. Membrane Proteins
• Proteins of membranes are globular proteins.
• Proteins that are buried partially or completely and found along the
distance of the membrane are called integral proteins
• Superficially attached on either side are peripheral proteins
• Pump proteins help in transferring substances by using energy against
concentration gradient (active transport).
• Receptor proteins bear appropriate sites for recognition of specific ligans .
10. Aquaporins – proteins that allow the
movement of water across
membrane by facititated diffusion.
Pump proteins
25. Water potential (ψ) is measured in
pressure units, kilopascals (kPa):
- Pure water ψ = O kPa.
Solutions ψ = negative:
e.g a dilute sucrose solution ψ = -250
kPa
a concentrated sucrose solution ψ = -
4000 kPa.
- Water moves by osmosis down a water
potential gradient, from a high ψ (- 250 kPA)
to a low ψ (- 4000 kPA).
