differentiation and specialisation

• What's differentiation?

  Differentiation is the process when different types of cells develop their specific set of cell structures and become specialised. 
• How's a sperm cell specialised?

  • Sperm cells are specifically designed for the effective transport of male DNA to the female DNA for sexual reproduction.
  • Head of the sperm contains half the genetic information ready for fertilisation with other half.
  • Acrosome contains digestive enzymes to penetrate egg cell.
  • Lots of mitochondria to provide the energy required for movement.
  • Long tail to help it swim quickly. 

  
• Differentiation:

  • Before cell does specific role within organism, must develop correct sub-cellular structures for the job. Occurs in differentiation which produces specialised cells.
  • Most differentiation in animal cells happens in the early stages of life, as the organism develops, however in most plants the ability to differentiate is never lost.
  • Stem cells are undifferentiated cells, have the ability to develop into different types of cells and they don’t have a specific structure/ function yet. Found in embryos and some adult tissues such as bone marrow.
• How are nerve cells specialised? Specialised for rapidly carrying electrical impulses around the body.

  • They have a long axon to carry the impulse over long distances.
  •  Dendrites, branches of nerve cells at both ends so they can connect and pass signals between one another. 
  • Myelin sheath, insulates axon which helps the impulse move along the nerve quickly, stopping electrical never signals cannot leak out.

  
• How are muscle cells specialised? Must be able to contract quickly, allowing force and motion

  • Lots of mitochondria to provide energy for the contraction.
  • Protein fibres that contract to make cell shorter so muscle can contract. Fibres also slide over to cause the muscle to contract.

   

  
• How are root hair cells specialised? Exchange surface, specialised for absorbing water and nutrients from the soil.

  • Long hair-like projections increasing SA for efficient absorption.
  • Vacuole, full of cell sap that is more concentrated than soil water which creates a water potential gradient for efficient water absorption.
  • Lots of mitochondria to provide energy for the active transport of mineral ions from the soil.

  
• How are xylem cells specialised? Xylem cells form the xylem vessel which transports water and dissolved ions in a plant.

  • open ended cells, series of dead hollow cells with no top and bottom cell walls, sub-cellular structures or cytoplasm allowing water to move upwards.
  • Lignin, strengthens cell walls of xylem

  
• How are phloem cells specialised? Phloem cells form the phloem which is responsible for the transport of sugars and amino acids around the plant. 

  • End walls of phloem cells contain small holes allowing food products to move up+down phloem vessels.
  • Unlike xylem cells, phloem cells are living despite also having very few subcellular structures.