Cell Transport

I. What is the driving force behind water movement?

• bulk flow

• waterfall

• water potential

II. What is diffusion?

• definition and model

III. What is osmosis?

• definition

• relationship to water potential

• examples of osmosis: Paramecium, animal cells rbc2 (stressed), Onion (plasmolysis images)

IV. Cell Membrane and Transport

1. permeability:definition

• permeability: predictions-a. hydrocarbons, b. water* and carbon dioxide, c. glucose and d. charged molecules (protons, potassium ion, chloride ion, amino acids, etc.)

* aquaporins

www.sbc.su.se/~gvh/ teaching/SweLL/module1.html

• Why are charged molecules not permeable through the membrane?

• special case: negatively charged ions

• Why is the cytoplasm generally negative?

2. Transport Systems

a. summary: passive/active transport compared with exocytosis and endocytosis

b. Passive Transport (facilitated diffusion)

• What determines the direction of diffusion?

• example: glucose transport in red blood cells

c. Active Transport

• Transport against the gradient: What determines the gradient?

• example of Nitella

• Ion	Water	Cytoplasm
  sodium	1.0 mM	14 mM
  potassium	0.1 mM	119 mM
  chloride	1.3 mM	65 mM

• Two types of active transport

• Primary ActiveTransport: the Na/K pump

• what are the typical concentrations of Na and K inside and outside of cells?

• the Na/K pump is electrogenic

• How does the Na/K pump work?

• What does the pump do for the cell?

• Secondary Active Transport

• Where does the energy come from to power secondary active transport?

• example: glucose transport from the lumen of the intestine into the blood stream animation

d. Endocytosis and Exocytosis

• What is it?

• Endocytosis: examples (uptake of bacteria by white blood cells; phagocytosis animation)

• Pinocytosis: example (uptake of cholesterol in blood)

• Goldstein & Brown Nobel Prize