Cell Membranes
Cell membrane= the boundary between the cell and its environment, regulates what enters and exits the cell.
The cell membrane is composed of phospholipids, cholesterol, proteins and carbohydrates.
Phospholipids
Make up the basic structure of the cell; the phospholipid bilayer.
Phosphate head- polar, hydrophilic. Arranged so that they face intra and extracellular fluid.
Lipid tail- non-polar, hydrophobic.
Cholesterol
Hydrogen and carbon atoms.
Found among the phospholipid bilayer.
They keep the phospholipid tails from solidifying when temperature drops as it separates the tails to prevent crystallisation.
Keeps the membrane flexible.
Makes the membrane less soluble- prevents some water soluble molecules from passing through it.
Proteins
Integral proteins within the membrane, peripheral proteins outside of the bilayer.
Can act as enzymes to catalyse reactions, receptors of hormones etc or as transporters of materials across the cell membrane by facilitated diffusion.
Carbohydrates (Chains) and Glycoproteins
Glycoproteins form H bonds with water molecules surrounding the cell.
Stabilise the membrane structure.
Can act as antigens to help cells recognise one another.
Receptors of hormones or neurotransmitters.
Carbohydrate chains are attached to glycoproteins outside of the plasma membrane.
Cushions the membrane.
Important in cell recognition and can also act as a 'glue' to attach cells together.
Cell Membranes Website for Notes
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