Cell membrane

• what is the function of cholesterol in the cell membrane

  regulates the fluidity of the cell
• how does cholesterol regulate the stability of the CSM when temps are too high and too low

  it sits between the phospholipids so when temps are low, it prevents them from getting too

  too high- they bind to the hydrophobic tails to stabilise them
• what else does cholesterol do

  it contributes to the impermeablility of the membrane to ions and increases mechanical strength and stability of membranes, without it membranes would break down
• what are glycoproteins and glycolipids composed of

  carbohydrate chain that are attached to either proteins or phospholipids
• what is the primary function of glycocalyx?

  to act as receptor molecules and bind to certain substances at the cell's surface
• what are the 3 main receptor types?

  • signalling receptors for hormones and neurotransmitters
  • receptors involved in endocytosis
  • receptors involved in cell adhesion and stabilisation (as the carbohydrate part can form hydrogen bonds with water molecules surrounding the cell )
• what do transport proteins do?

  create hydrophilic channels to allow ions and polar molecules to travel through the membrane

  each transport protein is specific to a particular ion or molecule
• what are the 2 types of transport protein?

  • channel proteins
  • carrier proteins
• when do membranes become less fluid?

  • An increased proportion of saturated fatty acid chains as the chains pack together tightly and therefore there is a high number of intermolecular forces between the chains
  • A lower temperature as the molecules have less energy and therefore are not moving as freely which causes the structure to be more closely packed
• when do membranes become more fluid?

  • An increased proportion of unsaturated fatty acid chains as these chains are bent, which means the chains are less tightly packed together and there are less intermolecular forces
  • At higher temperatures, the molecules have more energy and therefore move more freely, which increasing membrane fluidity