BIOL 1020 Lecture Notes - Lecture 16: Plant Cell, Contractile Vacuole, Osmoregulation

• School: Auburn University
• Department: Biology
• Course: BIOL 1020
• Professor: Dr.J.W.Zanzot

Document Summary

The plasma membrane is the boundary that separates the living call from its surroundings. The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others. Phospholipids are the most abundant liquid in the plasma membrane. Phospholipids are amphipathic molecules containing hydrophilic and hydrophobic regions. The fluid mosaic model states that a membrane is a fluid structure with a mosaic of various proteins embedded in it. The cholesterol has different effects on membrane fluidity at different temperatures: at warm temp. Cholesterol restrains movement of phospholipids: at cool temp. Variations in lipid composition of cell membranes of many species appear to be adaptations to specific environmental conditions. Ability to change the lipid compositions in response of temp changes has evolved in organisms that live where temps vary. A membrane is a collage of different proteins often grouped together embedded in the fluid matrix of the lipid belayer. Proteins determine most of the membranes specific functions.