Outline-1, BIO 2310, Membranes


A. Structure

1. Phospholipid bilayer

2. Protein “islands”

3. Selectively permeable

B. Movement across membrane

1. Diffusion [concentration gradient]

High concentration to low concentration

2. Osmosis

Diffusion of water across cell membrane

a. Osmotic pressure

Tendency of water to move by osmosis

b. Osmolality {solutes – milliosmoles/volume}

c. Tonicity [solution, solvent]




3. Facilitated diffusion = Passive transport

Diffusion along membrane protein carriers

4. Filtration

Solutions move across membrane by hydrostatic pressure; influenced by molecule size

5. Active transport

Movement against concentration gradient requiring metabolic energy

Na/K Pump (3 Na out/2 K in)

6. Endocytosis, Phagocytosis, Exocytosis

Processes taking in or discharging particles while maintaining the integrity of the cell membrane