Biological Membranes

What are the roles of cell membranes?

• cell recognition and signalling

• separating cell contents from external environment 

• regulating the transport of materials into or out the cell

What is the structure of plasma membrane? (7-10nm)

• formed of a bilayer of phospholipids with hydrophillic heads facing out the bilayer and hydrophobic tails facing into the bilayer

• contains different types of proteins within

• has cholestrol which regulates fluidity in the membrane

What is the fluid mosaic model?

• fluid: phospholipids can move freely within the membrane

• mosaic: different proteins embedded in the phospholipids (patchwork effect)

What is permeable through the plasma membrane?

• polar molecules diffuse rapidly across bilayer if theyre small enough eg Na+

• large uncharged polar molecules hardly permeate the bilayer eg glucose, NaCl

• small polar molecules readily dissolve in lipid bilayers and rapidly diffuse across them