Cell membranes

function of the cell surface membrane

function of the cell surface membrane

control movement of substances in and out of the cell

keep the cells contents together and separate from other cells

communication between cells

cell recognition

site for chemical reactions

flexibility for change of shape

what is cholesterol?

a lipid that sits in the phospholipid bilayer

what is the function of cholesterol?

to control fluidity and permeability, and stabilise the membrane

how does cholesterol stabilise the cell membrane?

it is relatively unreactive so stops cells from bursting when the temperature changes

how does cholesterol control the fluidity and permeability of the cell membrane?

it sits in between phospholipids so disrupts their regular structure, making it less fluid (more rigid)

how does the cell become more rigid and less permeable?

increase cholesterol levels

what are glycoprotiens

short polysaccharide chains attached to a protein on the membrane’s outer surface

how thick is the phospholipid bilayer? (roughly)

7-10nm

what is a phospholipid?

a lipid molecule with a glycerol, two fatty acid chains and a phosphate group

function of a plasma membrane

control entry and exit of substances into/out of a cell

structure of the cytoplasm

organelles suspended in gel-like cytosol. 70% water, and contains proteins, sugars, ions and fatty acids