chapter 2&3

• Cells


  The basic structural and functional unit of life
• Cell theory


  • All living things are composed of cells
  • Cells contain hereditary information
  • All cells arise from pre-existing cells
• SA/V


  Surface area to volume ratio
• Contents of a cell


  • Organelles which are membrane bound structures
  • Enable the cell to perform specific functions
• Organelles


  • Mitochondria
  • Chloroplast
  • Nucleolus
  • Nucleus
  • Plasma membrane
• Molecules in the plasma membrane


  • Phospholipids
  • Cholesterol
  • Proteins
  • Carbohydrates
• Function of the plasma membrane


  • To control what enters and leaves the cells
  • Semi permeable membrane, allows some substances to pass between the internal and external environment but not others
• Other functions of the plasma membrane


  • Recognising other cells or foreign cells/particles (recognises 'self' and 'not self')
  • Produce electric impulses in nerve and muscle cells
  • Receive information from the external environment
• Passive movement across the membrane


  1. Diffusion

  2. Facilitated diffusion

  3. Osmosis
• Osmosis


  The passive movement of water molecules across a semipermeable membrane from an area of low solute concentration to high
• Facilitated diffusion


  The passive transport of molecules across the membrane with the aid of transport proteins
• Diffusion


  The passive movement of molecules from an area of high concentration to an area of low concentration
• Active transport


  The transport of molecules across the plasma membrane from an area of low concentration to an area of high concentration, requires carrier proteins and the use of energy in the form of ATP
• Active transport


  Moves substances across membranes using energy, typically ATP, against their concentration gradient
• Facilitated diffusion


  Uses energy for transport proteins