Cell biology

• Ribosomes

  • where proteins are synthesised
• Flagella

  • tail like structure that rotate to help bacteria move
• Stages of mitosis

  • parents cell with 2 pairs of chromosomes
  • each chromosome replicates itself
  • chromosomes line up along the centre of the cell to divide and the copies move to opposite poles
  • each daughter cell has the same number of chromosomes and contains the same genes as the parent.
• Cell division by mitosis is used for:

  • growth and development of multicellular organisms
  • repairing damaged tissues
  • asexual reproduction
• Diffusion

  • the net movement of particles from an area of higher concentration to an area of lower concentration.
• There are examples of diffusion in living organisms

  • oxygen and carbon dioxide diffuse during gas exchange in lungs and plant leaves
  • urea diffuses from cells into the blood plasma for excretion by the kidney
  • digested food molecules from the small intestine diffuse into the blood
• Osmosis

  • is the diffusion of after from a dilute solution to a concentrated solution through a partially permeable membrane
• Active transport

  • moves substances against a concentration gradient, from an area low concentration to high concentration.
• Active transport

  • allows mineral ions to be absorbed into plants root hairs from very dilute solution in the soil
  • allows sugar molecules to be absorbed from lower concentrations in the gut into the blood, which has a higher concentration