Cell structure

• Eukaryotic cells


  Animal and plant cells have genetic material (DNA) that forms chromosomes and is contained within a nucleus
• Animal cell


  • Cell membrane controls the movement of substances into and out of the cell
  • Nucleus contains DNA
  • Mitochondria where energy is released through respiration
  • Ribosomes site of protein synthesis
  • Cytoplasm jelly-like substance where chemical reactions happen
• Plant cell


  • Cell wall made of cellulose which strengthens the cell
  • Permanent vacuole contains cell sap
  • Chloroplasts contain chlorophyll to absorb light energy for photosynthesis
• Prokaryotic cells


  • Bacteria have a single loop of DNA (no nucleus)
  • Have small rings of DNA called plasmids
  • Smaller than eukaryotic cells
• Comparing sub-cellular structures


  • Cell membrane
  • Cytoplasm
  • Cell wall
  • Nucleus
  • Chloroplasts
  • Permanent vacuole
  • Flagellum
  • Bacterial DNA loop
  • Plasmid DNA
• Light microscope


  • Allows viewing of samples
  • Relatively cheap
  • Moderate magnification
  • Moderate resolution
• Electron microscope


  • Uses a beam of electrons to form images
  • Allows viewing of sub-cellular structures
  • High magnification
  • High resolution
  • Expensive
  • Samples cannot be living
• Electron microscopes allow you to see sub-cellular structures, such as ribosomes, that are too small to be seen with a light microscope
• Magnification


  Actual size / Image size
• Cells in animals and plants differentiate to form different types of cells. Most animal cells differentiate at an early stage of development, whereas a plant's cells differentiate throughout its lifetime
• Specialised cells


  • Sperm cell
  • Red blood cell
  • Muscle cell
  • Nerve cell
  • Root hair
  • Palisade cell
• Sperm cell


  • Has a tail to swim to the ovum and fertilise it
  • Lots of mitochondria to release energy from respiration, enabling the sperm to swim to the ovum
• Red blood cell


  • No nucleus so more room to carry oxygen
  • Contains a red pigment called haemoglobin that binds to oxygen molecules
  • Flat bi-concave disc shape to increase surface area-to-volume ratio
• Muscle cell


  • Contains protein fibres, which can contract to make the cell shorter
  • Contains lots of mitochondria to release energy from respiration, allowing the muscles to contract
• Nerve cell


  • Branched endings, called dendrites, to make connections with other neurones or effectors
  • Myelin sheath insulates the axon to increase the transmission speed of the electrical impulses
• Root hair


  • Long projection speeds up the absorption of water and mineral ions by increasing the surface area of the cell
  • Lots of mitochondria to release energy for the active transport of mineral ions from the soil
• Palisade cell


  • Lots of chloroplasts containing chlorophyll to absorb light energy
  • Located at the top surface of the leaf where it can absorb the most light energy