Chapter 7: Membrane Structure and Function. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!.
If you are having trouble
understanding lecture material:
Try reading your text
before attending lectures.
And take the time to read it well!
The “ability of the cell to discriminate in its chemical exchanges with the environment is fundamental to life, and it is the plasma membrane that makes this selectivity possible.”Lipid Bilayer
For more on this history, see: http://www1.umn.edu/ships/9-2/membrane.htm
“Cholesterol reduces membrane fluidity at moderate temperatures by reducing phospholipid movement, but at low temperatures it hinders solidification by disrupting regular packing of phospholipids.”Campbell & Reece (2005) p. 126
Protein diffusion is not as fast as phospholipid diffusion
Proteins attached to cytoskeleton or ECM don’t move
Know definition of transmembrane protein
Note distinct orientation
Membrane asymmetry allows cells to automatically differ their intracellular environment from that existing extracellularly
Note the equivalent orientation of endomembrane lumen and extracelullar environmentMembrane Protein Trafficking
Note the orientation of carbohydrate (always lumen or outside of cell)
Active transport is pumping against concentration gradients
Down water’s concentration gradient
More solute in than out
The parallels between the properties of transport proteins and enzymes are fairly extensive, to the point where one may consider a transport protein simply as an enzyme-like protein that “catalyzes” the physical process of movement from one side of a membrane to another
Note that ATP-mediated phosphorylation of glucose inside of cell drives this transport, making it an example Group Translocation
The sodium-potassium pump is a specific (and important) example ATP-powered active transport
Why is the sodium-potassium pump considered to be an eletrongenic pump?
Allows digestion in confined space
Taking up solids
Taking up fluids
Increases absorptive membrane area
A way of taking up specific substances