1.4

• Specialisation in animal cells

  How cells differentiate to form specialised cells
• Animal cells may be specialised to carry out a particular function
• The structure of different types of animal cells relates to their function
• As an organism develops, cells differentiate to form different types of specialised cells
• Most types of animal cells differentiate at an early stage of development, whereas many types of plant cells retain the ability to differentiate throughout life
• As a cell differentiates, it gets different subcellular structures that enable it to carry out a particular function
• Some specialised cells, such as egg and sperm cells, work individually. Others are adapted to work as part of a tissue, an organ, or a whole organism
• Nerve cells


  • They provide a rapid communication system between the different parts of the body
  • They have lots of dendrites to make connections to other nerve cells
  • They have an axon that carries the nerve impulse from one place to another
  • The nerve endings or synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle using special transmitter chemicals
  • They contain lots of mitochondria to provide the energy needed to make the transmitter chemicals
• Muscle cells


  • They can contract and relax
  • Striated muscle cells work together in tissues called muscles
  • Muscles contract and relax in pairs to move the bones of the skeleton
  • Smooth muscle cells form one of the layers of tissue in the digestive system and they contract to squeeze the food through the gut
  • They contain special proteins that slide over each other making the fibres contract
  • They contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax
  • They can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract
• Sperm cells


  • They contain the genetic information from the male parent
  • They have a long tail that whips from side to side to help move the sperm through water or the female reproductive system
  • The middle section is full of mitochondria, which transfer the energy needed for the tail to work
  • The acrosome stores digestive enzymes for breaking down the outer layers of the egg
  • A large nucleus contains the genetic information to be passed on