2.2 - Specialised Cells

Specialised cells and their functions

• Most cells are specialised: their structure is adapted to a particular function.
• The seven specialised cells below each pair a function with the structures that suit it.

Ciliated cell

• Function - Moves substances along a surface.
• Has cilia - hair-like structures on its top surface that beat to move substances in one direction.
• Lines the trachea and bronchi, sweeping mucus and trapped particles up towards the throat so they don't reach the lungs.
• The mucus is made by goblet cells in the airway lining; it traps pathogens and particles, and the cilia sweep it to the throat to be swallowed - protecting the breathing system and keeping the lungs clear.

Root hair cell

• Function - Absorbs water and mineral ions.
• Sits on the surface of a plant root and grows out into a long hair sticking into the soil.
• This gives a large surface area for absorption.

Palisade mesophyll cell

• Function - Carries out most of a leaf's photosynthesis.
• Sits in a layer near the top of the leaf, where it receives the most light.
• Packed with chloroplasts - the structures in which photosynthesis takes place.
• Long and thin, so many can be packed into the same space.

Neurone (nerve cell)

• Function - Conducts electrical impulses from one part of the body to another.
• Long, so it can carry impulses over a large distance.
• Has branched connections at its ends to link with other neurones and form a network through the body.

Red blood cell

• Function - Transports oxygen from the lungs to the rest of the body.
• Biconcave disc shape (squashed in the centre) - gives a large surface area for absorbing oxygen.
• Filled with the red pigment haemoglobin, which carries the oxygen.
• Has no nucleus, leaving more room for oxygen.

Sperm and egg cells

Sperm and egg cells are the gametes - the sex cells of reproduction.

• Sperm cell:
  • Long flagellum (tail) and a streamlined head to swim to the egg.
  • Many mitochondria in its middle section for energy.
  • Enzymes stored in the acrosome at its head to digest through the egg's membrane.
• Egg cell:
  • Large, with nutrients in its cytoplasm to nourish the developing embryo.