stem cells and differentiation

  • Created by: aryan26
  • Created on: 09-04-19 10:57
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  • stem cells and differentiation
    • stem cells are unspecialised cells- they can develop into any type of cell
      • stem cells differentiate into specialised cells
        • in animals stem cells are used to replace damaged cells
        • in plants stem cells are needed to make new shoots and roots as they are always growing
        • they can divide to produce more undifferentiated stem cells
    • cells in the bone marrow differentiate into blood cells- erythrocytes (red) neutrophils (white)
      • in plants stem cells are found in the meristems
        • in the root, stem cells of the vascular cambium divide and differentiate to become xylem vessels and phloem sieve tubes
    • specialised animal cells
      • neutrophils- white blood cell that defends against disease
        • flexible shape allows them to engulf particles
        • many lysosomes in the cytoplasm to break down engulfed particles
      • erythrocytes- red blood cells that carry oxygen in the blood
        • biconcave disc shape gives a large SA for gas exchange
        • have no nucleus so there's the maximum room for haemoglobin
      • epithelial cells- cover surfaces of organs
        • joined by interlinking membranes and a membrane at their base
        • ciliated epithelia in the airways- have cilia to move particles away
        • squamous epithelia are very thin to allow efficient gas exchange
      • sperm cells- male sex cells
        • have flagellum so they can swim to the egg
        • lots of mitochondria to provide energy to swim
        • acrosome contains digestive enzymes so they can penetrate the surface of the egg
    • specialised plant cells
      • palisade mesophyll cells- carry out photosynthesis
        • contain many chloroplasts to absorb a lot of sunlight
        • walls are thin so carbon dioxide can easily diffuse into the cell
      • root hair cells- absorb water and mineral ions from the soil
        • large SA to absorb the maximum amount
        • thin permeable cell wall
        • extra mitochondria to provide energy for active transport
      • guard cells- found in pairs with a gap between them to form a stoma
        • stoma are tiny pores in the surface for gas exchange
        • in the light, guard cells take up water and become tugid
          • thin outer walls and thin inner walls makes them bend outwards opening the stomata- allows gas exchange

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