movement of substances

components of cell membrane

phospholipids

different types of proteins

structure of phospholipids in cell membrane

• exhibit both hydrophobic and hydrophilic properties: phospholipid molecule consists of hydrophilic head and 2 hydrophobic tails

• arranged as a bilayer in all membrane structures

• hydrophilic heads face outwards into aqueous cytoplasm and aqueous extracellular space

• hydrophobic tails face each other in the middle of the bilayer to form a hydrophobic core

function of phospholipids in cell membrane

• bilayer arrangement of phospholipids forms a barrier between aqueous environment and the cell cytoplasm

• phospholipid bilayer allows small, hydrophobic substances (e.g. oxygen and carbon dioxide) to diffuse across

structure and position of proteins in the cell membrane

there are many different proteins embedded in the phospholipid bilayer

• peripheral proteins: bound to one side of the membrane

• integral proteins: span across the entire phospholipid bilayer (e.g. those involved in transporting substances across membranes)

• glycoprotein: have carbohydrate chains attached to them

functions of proteins in cell membrane

• transport: some proteins move or allow specific substances such as large or hydrophilic molecules to move across the phospholipid cell membrane (e.g. aquaporins are membrane channel proteins that transport water molecules

• cell-to-cell recognition