1.4 Specialisation in animal cells

• Large organisms are made of many cells. As the organism develops, some cells become specialised to preform a particular function. The cells become different from each other (they differentiate). Specialised cells may work individually (eggs and sperm) or as part of a tissue, an organ, or a whole organism 
• Specialised cells may contain large numbers of particular sub-cellular structures, for example, muscle cells require a lot of energy so they contain many mitochondria.  
• Nerve cells are specialised to carry electrical impulses around the bodies of animals.
• Nerve cells have:

  • Many dendrites to make connections to other nerve cells
  • An axon to carry the impulse from one place to another, such as from your spine to your big toe
  • Nerve endings or synapses, which pass impulses to other cells by producing transmitter chemicals
  • Many mitochondria in the synapses to transfer the energy needed to make the transmitter chemicals
• The nucleus contains genetic material that controls how the cell functions. It also has a role in controlling growth and division.
• Muscle cells can contract and relax. Striated (striped) muscle cells are found in the muscles that enable your body to move. Smooth muscle cells are found in the tissues of the digestive system and contract to move food along to gut. So that they can contract, striated muscle cells contain

  • Special proteins that slide over each other
  • Many mitochondria to transfer the energy needed for chemical reactions
  • A store of glucose that can be broken down and used in respiraton to transfer energy
• Muscle cells contain a lot of mitochondria. Why?


  To transfer the amount of energy needed
• Which organ system contains nerve cells


  The Nervous System
• Sperm cells carry the genetic information from the male parent. They are specialised to move through water or the female reproductive system to reach the egg. Sperm cells have:

  • A long tail that whips from side to side to move the sperm
  • A middle section full of mitochondria to transfer the energy needed by the tail to move
  • An acrosome to store digestive enzymes to break down the outer layers of the egg
  • A large nucleus to contain the genetic information