1.1.3 Cell Specialisation

Specialised Cells in Animals:

1. Sperm Cells:

• Function: Carry the male's DNA to the egg cell for reproduction.
• Adaptations:
• Streamlined head and long tail for swimming.
• Many mitochondria to provide energy for movement.
• Acrosome with digestive enzymes to penetrate the egg cell membrane.

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2. Nerve Cells:

• Function: Transmit electrical signals quickly across the body.
• Adaptations:
• Long axon for carrying impulses over long distances.
• Dendrites to form connections with other nerve cells.
• Nerve endings with mitochondria to produce neurotransmitters.

3. Muscle Cells:

• Function: Contract to move bones (striated muscle) or squeeze (smooth muscle) to control blood pressure.
• Adaptations:
• Special proteins (myosin and actin) for contraction.
• Many mitochondria for energy production.
• Store glycogen for respiration.

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Specialised Cells in Plants:

1. Root Hair Cells:

• Function: Absorb water by osmosis and mineral ions by active transport from the soil.
• Adaptations:
• Large surface area due to root hairs.
• Large permanent vacuole to speed up water movement.
• Mitochondria for energy to transport mineral ions.

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2. Xylem Cells:

• Function: Transport water and mineral ions from roots to shoots.
• Adaptations:
• Lignin deposition to strengthen cell walls and create a continuous tube.
• Spirals of lignin to withstand water pressure.

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3. Phloem Cells:

• Function: Transport products of photosynthesis (food) to all parts of the plant.
• Adaptations:
• Cell walls form sieve plates for substance movement.
• Companion cells with mitochondria provide energy to sieve cells.