B2.1 Cells


Animal Cell Structure

Animal cells

  • Nucleus
    • Controls cell chemical reactions and cell division
  • Cytoplasm
    • Where most of the chemical reactions take place
  • Cell membrane
    • Controls the passage of substances in and out of the cell
  • Mitochondria
    • Where most energy is released in respiration 
    • Release energy from glucose by respiration to make cellular energy
  • Ribosomes
    • Where protein synthesis occurs
    • Join amino acids in correct order to make a specific protein. Each protein is coded for by a gene


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Plant Cell Structures

Plant and algal cells

  • Chloroplasts
    • Use light energy to make glucose and oxygen from carbon dioxide and water by photosynthesis
  • Cell Wall
    • Made from cellulose
    • Strengthens the cell
    • Keeps the cell's shape
  • Vacuole
    • Filled with cell sap
      • Contains water, mineral ions and dissolved chemicals
    • Acts like a reservoir for the cell
    • Supports the cell


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Bacterial and Yeast Cells

Bacterial Cells

  • Simpler cell structure than plant and animal cells
  • Genes form a loop that is not in a nucleus
  • Cytoplasm
  • Cell wall
    • Made of different materials to cell walls in plants
  • Cell membrane


Yeast Cells

  • Single-celled organism (fungus)
  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Cell wall
    • Made of different materials to cell walls in plants
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Specialised Cells

  • Muscle cells
    • Contain fibrils that contract
    • Muscle can get shorter and move parts of the body
  • Sperm cells
    • Tail for swimming to the egg cell for fertilisation
  • Nerve cells
    • Long fibre
    • Conduct electrical impulses around the body
  • Red blood cells 
    • No nucleus and concave shape
    • To hold more haemoglobin, and large surface area
  • Palisade cells
    • Lots of chloroplasts
    • Carries out photosynthesis
  • Egg cells
    • Genetic info
    • Lots of cytoplasm
    • Nutrients for embryo
    • Protective layer outside the egg
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Diffusion is the spreading of the particles of a gas, or of any substance in a solution, resulting in a net movement

Net movement: sum of movement of all the particles. In diffusion, the net movement is from the area of high concentration to an area of lower concentration 

  • Before diffusion
    • The number of (green) particles decreases as you go down their concentration gradient
  • After diffusion
    • No concentration gradient
    • Particles evenly mixed
    • Particles still moving around

The greater the difference in concentration, the faster the rate of diffusion. 

Many dissolved substances (such as glucose and mineral salts) and gases (such as oxygen and carbon dioxide) can cross cell membranes by diffusion

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