Cells Specialisation

• A stem cell is an undifferented cell capable of becoming any type of cell
• once the stem cell is differentiated, the cell usually loses this ability to change
• some stem cells can retain the ability to change e.g. bone marrow
• Sperm cell: streamlined shape to swim easier, lots of mitochondria to do aerobic respiration and provide energy for swimming, tail to swim, acrosome of digestive enzymes to break into egg cell, nucleus has half the genetic info
• muscle cell: have special proteins for contracting muscle, many mitochondria to do aerobic respiration to provide energy, store glycogen for breaking down to glucose to use in respiration
• root hair cell: 'hair' increases surface area for more water absorption, large vacuole - speeds up osmosis, many mitochondria for aerobic respiration to provide energy for transport of mineral ions
• palisade cell: contains lots of chloroplasts and has a high concentration and this is on the outer layer of leaf to absorb sunlight, large vacuole keeps them rigid
• xylem vessel: long tube with no cross walls so water flows easily through it, thick lignin wall makes it strong enough to support plant weight, dead cells means they don’t need nutrients or oxygen
• nerve cell: dendrites receive signals from other nerve cells, axon transmits signal along length of cell, myelin sheath insulates axons so electrical impulses travel faster, synapse where neurotransmitters released at end of axon to stimulate next neurone
• red blood cell: biconcave disc shape maximises surface area for gas exchange, haemoglobin molecules bind O2 and CO2, no nucleus/organelles because there isn’t room and they aren’t needed
• epidermal cell: waxy cuticle prevents water loss by evaporation, pigments protect against UV light damage, stomata allow gas exchange but prevent too much water loss