Life 102 - (2)

1. The cell and its organelles are surrounded by one or more membranes.

2. Function of membranes:

   a.) to separate compartments

   b.) to control traffic of molecules into and out of compartments - (Selectively permeable)

3. Membrane Structure: Fluid mosaic model - phospholipid bilayer with proteins embedded in the bilayer.

   a.)(Fluid part of the model first) determined by Phospholipid bilaryer -

    i. Structure of phospholipids (non-polar and polar parts) means that they easily (spontaneously)form a bilayer when exposed to water.

    ii.) Experiments with labeled proteins shwos that proteins can move within the membrane - fluid. Most membranes have fluidity similar to salad oil.

    iii.) The phospholipids cna move freely in lateral direction (10^7 per sec) but not across membrane (1 per month) (hydrophilic part has a hard time getting through hydrophobic layer).

   iv.) Membrane fluidity determined by the type of phospholipid (lipids with single vs. double bonds) Saturated lipids - more tightly packed - more viscous membrane. Unsaturated lipids ( double bonds) - less tightly packed - less viscous (more fluid).

   v.) Cholesterol.

NOTES ON THE EXAM:

Student number etc.

KEEP EXAM!

Will be posted on Tuesday

Keeping the two separate -- before you start taking the exam -- flip test over and start writing formulas.