Cell Specialization
Biology: IB Diploma Higher Level, topic 6.3.1
Specialised Cells
In complex multicellular organisms, cells gain specific features. This is called specialisation. Specialised cells are organised into groups to perform a function. Examples of specialised cells include:
Neutrophils
- Neutrophils are phagocytic leukocytes which are involved in one of the early lines of defence against pathogens by removing bacteria that have entered the body.
- Neutrophils have a nucleus with 2-5 lobes and contain organelles, called lysosomes.
- Lysosomes digest the engulfed pathogens.
Squamous epithelial cells
- Squamous epithelial cells are round and flat with a small, centrally located nucleus.
- The cells fit together to form a covering or lining.
- When arranged in a single layer (simple epithelia), they facilitate diffusion in tissues, such as:
- Gas exchange in the lungs.
- Nutrient and waste exchange in blood capillaries.
Ciliated epithelial cells
- Ciliated epithelial cells, such as the pseudostratified columnar epithelia in the respiratory tract, have cilia on the apical surface of each cell.
- The cilia enhance the movement of mucous and trapped particles out of the respiratory tract through a wafting motion.
- This helps protect the body from pathogens and harmful material that has been inhaled.
Specialised Cells 2
Some more examples of specialised cells are:
Sperm cells
- Sperm cells are the male reproductive cells (male gametes), which fuse with an egg cell during fertilisation to form a zygote.
- To ensure the zygote has one complete diploid set of chromosomes, both egg and sperm cells are haploid and only one sperm fuses with one egg.
- The acrosome in the head of the sperm contains digestive enzymes which degrade the zona pellucida surrounding the egg cell.
- This allows the sperm plasma membrane to fuse with the egg plasma membrane.
Guard cells
- Guard cells surround the stomatal pore and control the opening and closing of the stomata.
- The osmotic state within the guard cells determines their turgor.
- When the guard cells are flaccid, stomata close.
- When the guard cells are turgid, stomata open.
- Turgor is regulated by the active transport of ions, such as K+ and H+ across the plasma membrane.
Root hair cells
- Root hair cells are specialised to increase the efficiency of water absorption and the uptake of minerals required for the plant’s survival.
- The root hairs are long projections that increase the surface area that the plant can use to absorb water and minerals.
- These cells are located underground and so don't contain chloroplasts as there is no light for photosynthesis.
Test yourself on Cell Specialization
Which organelle in a neutrophil is responsible for digesting engulfed pathogens?
Which of these statements most accurately describe squamous epithelial cells?
Which of these is NOT a feature of red blood cells that allows them to be specialised for their function?
Which of these specialised cells is NOT found in animals?