cell membranes

• Components of the plasma membrane

  Lipids (phospholipids and cholesterol), proteins, and carbohydrates
• Hydrophilic head


  Consists of a phosphate containing group attached to a glycerol molecule
• Hydrophobic tails


  Contain either saturated or unsaturated fatty acid, are long hydrocarbon chains
• Fatty acids is the cause of membrane fluidity since absence of double bonds increases fluidity
• Membrane orientation retains during transfer between cell compartments due to specific proteins and lipid composition. Proteins like SNAREs and Rab proteins help membranes fuse correctly, preserving orientation.
• Integral proteins


  Are permanently embedded within the cell membrane
• Peripheral proteins


  Are attached to the surface of the membrane
• Helping cells recognize each other and providing protection for cells is the function of carbohydrate coating on the membrane
• Active transport


  Requires energy for the movement of molecules
• Passive transport


  Does not require energy for the movement of molecules
• Sodium potassium pump


  Creates gradients of both sodium and potassium ions