Specialised Cells Notes

Specialised Cells

Learning Goals

  • Understand examples of specialised cells in plants and animals.

Goblet and Ciliated Epithelial Cells

  • These cells line lung passages.
  • Goblet cells:
    • Produce mucus, which traps dust, pathogens, and small particles.
  • Ciliated epithelial cells:
    • Possess cilia, small cytoplasmic extensions at one end of the cell.
    • Protein fibers move cilia like a wave.
    • Movement carries mucus out of airways to the back of the throat.
    • Swallowed mucus enters the stomach, where acid kills pathogens.

Muscle Cells

  • Three types: skeletal, cardiac, and smooth.
  • All muscle cells are elongated and contain protein fibers.
  • Protein fibers shorten/contract the cell (function).
  • Main functions:
    • Structural support.
    • Movement.
    • Generating heat.

Red Blood Cells

  • Most of blood is made of red blood cells.
  • Red color is due to haemoglobin, a pigment.
  • Oxygen combines with haemoglobin to form oxyhaemoglobin.
  • Function: Transport oxygen from the lungs to body cells for respiration.

Red Blood Cell Structure and Function

  • Shape: Biconcave.
  • Size: Small to fit into tiny capillaries.
  • Surface Area to Volume Ratio: Large, to absorb more oxygen.
  • Nucleus: Absent, to maximize space for haemoglobin.

Nerve Cells

  • Axon: Long cytoplasmic extension that carries messages as electrical impulses.
  • Myelin Sheath: Fatty substance surrounding the axon; insulates the fiber to speed up impulse travel.

Gametes (Sex Cells) - Sperm and Egg

  • Specialised for reproduction.
  • Contain half a set of chromosomes each.
  • Fertilization: combining sperm and egg creates a new organism with a complete set of chromosomes.
  • Egg Cell structure
    • A lot of cytoplasm to store nutrients and provide organelles to the new cell after fertilisation
    • Surrounded by a cell surface membrane
    • Surrounded by a layer of protective jelly
  • Sperm cell structure
    • Tail for swimming
    • This region contains many mitochondria to make energy
    • Nucleus Head

Plant Root Hair Cells

  • Root hairs are cytoplasmic extensions from epidermal cells lining the outside of the root.
  • Function: Increase surface area for water absorption from the soil.

Xylem Vessels

  • Water moves through xylem vessels to other parts of the plant.
  • Structure:
    • Elongated cells placed end-to-end, forming long, continuous tubes.
    • Cell walls are thickened with lignin for strength and structural support.
    • Lignin makes the cell wall impermeable.
    • No cytoplasm (cell contents die).
    • Lumen (space inside) is hollow, providing no resistance to water flow.