Cell Biology: Cell Specialisation and Differentiation

• What is the definition of cell differentiation?


  The process by which cells become specialized in structure and function.
• Most differentiation occurs as an organism develops. In most animal cells, the ability to differentiate is then lost after the cell is specialised. However, lots of plant cells don't lose this ability. The cells that differentiate in mature animals are mainly used for repairing and replacing cells, such as skin or blood cells.
• Sperm cell:

  • Lots of mitochondria: Provide the energy required for swimming
  • Digestive Enzymes: Used to break a hole into the egg when the sperm reaches it
  • The Flagellum: Allows the sperm cell to swim through the uterus and Fallopian tubes to reach the egg

  A) Tail

  B) Midpiece containing mitochondria

  C) Haploid nucleus

  D) Acrosome
• Nerve Cell:

  • Long body so electrical signals don't slow down
  • Branched connections

  Nerve cells are specialised for rapid signalling. The function of nerve cells is to carry electrical signals from one part of the body to another. These cells are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body

  A) Cytoplasm

  B) Cell Membrane

  C) Nucleus

  D) Axon

  E) Nerve Ending

  F) Dendrite

  
• Key Point:

  • Specialised cells have a specific role in the body
  • To help them fulfil that role they have a specific shape or structure
  • They have specific amounts of different organelles
• Muscle Cells:

  Muscle Cells are specialised for contraction. The function of a muscle cell is to contract quickly. These cells are long (so they have space to contract) and contain lots of mitochondria, providing them with sufficient energy to contract and move

  A) Heart Muscles

  B) Smooth Muscle Cells

  C) Skeletal Muscle

  
• Root Hair Cell:

  • Has no chloroplasts as it is in the soil and therefore can't carry put photosynthesis
  • Lots of mitochondria as the nutrients move against the concentration gradient and therefore requires energy
  • Thin walls for a shorter diffusion pathway
  • Larger surface area means more area for nutrients to diffuse from

  
• Xylem Cells:

  • To form the xylem tubes that go through the plant, the cells are long and joined end to end
  • Xylem cells are hollow in the centre so that substances can flow through them
  • Xylem cells only transport water upwards

  A) Walls are thickened with lignin

  B) Xylem

  
• Phloem Cell:

  • To form the phloem tubes that go through, the cells are long and joined end to end
  • Phloem cells have very few sub - cellular structures, so that substances can flow through them
  • Phloem cells transport sugars, minerals and water both ways the tubes

  A) Phloem

  B) Companion Cell

  C) Cytoplasm

  D) Sieve Plate