Plasma membranes, transport, tonicity and water potential

Learning objectives

Describe the fluid mosaic model, explaining how the phospholipid bilayer, embedded proteins, cholesterol and glycoproteins contribute to membrane structure and selective permeability

Compare passive transport by simple diffusion, facilitated diffusion through channel and carrier proteins, and osmosis, with active transport driven by ATP through pumps such as the sodium–potassium pump

Explain endocytosis and exocytosis as bulk transport mechanisms and describe how they maintain membrane surface area

Predict the direction of net water movement between a cell and its surroundings from the solute concentrations, using the terms hypertonic, hypotonic and isotonic, and describe the effects on plant and animal cells

Calculate water potential from solute potential and pressure potential, and use the result to predict water movement in a plant tissue or a dialysis-tubing investigation

Design an investigation into the effect of solute concentration on mass change in plant tissue, identifying the variables and explaining how percent change in mass is used to find the isotonic point