Cell transport

• Plasma membrane


  • partially permeable
  • separates the cells contents from the external environment allowing different conditions to be established
• membranes are permeable to:


  • water
  • carbon dioxide
  • oxygen
• double membranes


  nucleus, chloroplast and mitochondria
• phospholipids


  • phosphate group
  • glycerol
  • saturated/unsaturated fatty acid
  • hydrophilic head
  • hydrophobic tail
• Ion channels


  allow water-soluble molecules/ions through
• transport proteins


  transport specific molecules
• glycoproteins


  a protein with a polysaccharide chain extending outwards

  • involved in cell recognition
• receptors


  binding site for hormones
• glycoprotein


  carbohydrate chains attached to extrinsic proteins

  -> receptor for hormones and neurotransmitters
• glycolipid


  carbohydrate chain covalently bonded with lipids

  -> maintain stability
• phospholipid bilayer


  polar head and two non-polar tails

  -> allows for membrane fluidity and flexibility
• protein channel


  water filled tube

  -> allow water soluble ions to diffuse across
• cholesterol 


  4 hydrocarbon rings

  -> controls membrane fluidity
• intrinsic protein


  whole width of membrane

  -> move across the membrane
• extrinsic protein


  inner or outer surface of membrane

  -> mechanical strength