Midterm paper

CELL BIOLOGY LAB Plasma Membrane Permeability

Pre-lab Resources Dr. Lisa Brinn

Membrane Permeability ■ Barrier effectiveness

– Greater its permeability – easier for substances to cross – Impermeable – nothing cross the membrane – Freely permeable – no resistance during crossing

■ Plasma membrane – Selectively permeable ■ In between impermeable and freely permeable ■ Factors determining permeability:

– Substance’s size – Electrical charge – Molecular shape – Solubility

Passive vs Active Processes ■ Passive Process

– Simple diffusion, facilitate diffusion and osmosis

■ Active Process – Active transport, endocytosis and exocytosis

Passive Process

Water Movement With Cells ■ Isotonic

– Equal tension

■ Osmosis occurs when there is an imbalance of solutes – Hypertonic ■ Water leaves

– Hypotonic ■ Water enters

Active Process

Endocytosis and Exocytosis