6.3.1

Cell Specialization

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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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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.
Jump to other topics
1

Unity & Diversity - Molecules

2

Unity & Diversity - Cells

3

Unity & Diversity - Organisms

4

Unity & Diversity - Ecosystems

5

Form & Function - Molecules

6

Form & Function - Cells

7

Form & Function - Organisms

8

Form & Function - Ecosystems

9

Interaction & Interdependence - Molecules

10

Interaction & Interdependence - Cells

11

Interaction & Interdependence - Organisms

12

Interaction & Interdependence - Ecosystems

12.1

Populations & Communities

12.2

Transfers of Energy & Matter

13

Continuity & Change - Molecules

14

Continuity & Change - Cells

15

Continuity & Change - Organisms

16

Continuity & Change - Ecosystems

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