Membrane Structure & Function

1. Membrane Structure & Function

2. Membrane Models 1972- Present Fluid-Mosaic Model 1935-1970 Sandwich Model

6. Membrane Transport(Passive) 1 2 Glucose, amino acids

7. Diffusion Steepness of concentration gradient Temperature Mass of diffusing substance Surface area Diffusion distance

8. 2 types of membrane transport Passive vs Active

9. Channel-mediated Facilitated Diffusion of Potassium ions through a Gated K + Channel

10. Extracellular fluid Extracellular fluid Extracellular fluid Plasma membrane Plasma membrane Plasma membrane Cytosol Cytosol Cytosol Glucose transporter Glucose transporter Glucose transporter Glucose Glucose Glucose 1 1 1 Glucose gradient Glucose gradient Glucose gradient 2 2 3 Glucose

11. http://trc.ucdavis.edu/biosci10v/bis10v/media/ch04/tonicity.htmlhttp://trc.ucdavis.edu/biosci10v/bis10v/media/ch04/tonicity.html

12. Crenation Hemolysis Cytolysis

13. Plasmolysis – the shriveling of the cell membrane due to loss of water (osmosis) Turgor pressure – the force directed against the cell wall after the influx of water (osmosis)

14. Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.

15. Requires Energy: ex.: thyroid gland concentrates Iodine glucose is completely absorbed by digestive tract sodium potassium pump

16. Extracellular fluid Na+ gradient 3 Na+ expelled 2K+ Na+/K+ ATPase P 3 Na+ Cytosol K+ gradient ATP 2 K+ imported 1 2 3 4 P ADP Active Transport I. Solutes are transported across plasma membranes with the use of energy, from an area of lower concentration to an area of higher Concentration *Sodium-potassium pump *Thyroid gland *Intestines (glucose) II. 2 sources of energy 1. ATP (Primary active transport) 2. Energy stored in Ion concentration gradients (Secondary active transport) **40% of a cell’s ATP is used for Primary active transport  Cyanide shuts down active tranport by turning off ATP production 3 Na+ Cytosol K+ gradient 1

18. Secondary Active Transport Mechanisms • Antiporters carry two substances across the membrane in opposite directions (Digitalis) • Symporters carry two substances across the membrane in the same direction

19. Endocytosis – taking in large amounts of material (bulk flow)

20. Ex. LDL cholesterol (bad cholesterol)