Topic 2A.1 Cell Membranes

cell membrane

the selectively permeable membrane which surrounds the cytoplasm of a cell, acting as a barrier between the cell contents and their surroundings

organelles

sub-cellular bodies found in the cytoplasm of cells

enzymes

proteins that act as biological catalysts for a specific reaction or group of reactions

vesicles

membrane ‘bags’ that hold secretions made in cells

phospholipids

chemicals in which glycerol bonds with two fatty acids and an inorganic phosphate group

polar lipids

lipids with one end attached to a polar group (eg. a phosphate group) so that one end of the molecule is hydrophilic, and one end is hydrophobic

hydrophilic

a substance with an affinity for water that will readily dissolve in or mix with water

hydrophobic

a substance that tends to repel water and that will not dissolve in or mix with water

monolayer

a single closely packed layer of atoms or molecules

micelles

a spherical aggregate of molecules in water with hydrophobic areas in the middle and hydrophilic areas outside

bilayer

a double layer of closely packed atoms or molecules

unit membrane

a lipoprotein membrane which is composed of two protein layers enclosing a less dense lipid

fluid mosaic model

the current model of the structure of the cell membrane including floating proteins forming pores, channels and carrier systems in a lipid bilayer

gated channels

protein channels through the lipid bilayer of a membrane that are opened or closed, depending on conditions in the cell

glycoproteins

conjugated proteins with a carbohydrate prosthetic group