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2.3 |
Living Processes of Multicellular Organisms |
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Specialised cells in animals and humans: |
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Epithelium cell
Structural adaptation: Thin cells; arranged closely
Function:
- Provide protection
- Aid in gaseous exchange
- Helps in nutrients absorption, secretes mucus
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Muscles cell
Structural adaptation:
- Contains many fibres; aid in movement
- Have many mitochondria; provide energy for muscle contraction
Function: Contracts to produce movement
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Nerves cell
Structural adaptation:
- Have long dendrites and axon
- Axons covered with myelin sheath; faster transmission
Function: Transmits nerve impulse from one part to another part of the body
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Red blood cell
Structural adaption:
- Contains haemoglobin; transport oxygen
- Elastic and flexible; allow the blood to squeeze through thin blood capillaries
- Has a biconcave disc shape; increases the ratio of surface area per volume; increase the diffusion of respiratory gases
Function: Transports respiratory gases
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White blood cell
Structural adaption: Can change shape; easily squeeze through the tiny blood vessels to the interstitial space to hunt the pathogens
Function: Protects the body from pathogens
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Sperm cell
Structural adaption:
- Has a long tail; helps the sperm to move
- Contains mitochondrion; provide energy for the sperm to swim
- Contains enzymes; helps the sperm to penetrate the ovum
Function: Fertilises the ovum
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Specialised cells in plants: |
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Spongy palisade mesophyll cell
Structural adaptation: Packed loosely; efficient gaseous exchange
Function: Facilitate gas permeation
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Xylem
Structural adaptation:
- Consists of porous long tubes; to transport substances efficiently
- Strengthen by lignin; to prevent the xylem from collapse
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Function: Transport water and mineral salts from the roots to a whole plant |
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Sieve tubes
Structural adaptation:
- Matured sieve tubes have no nucleus; provide more space for transportation
- Have sieve plates
- No lignin
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Function: Transport organic substances; sucrose, amino acids and hormones from the shoots to other parts of the plant |
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Root hair cell
Structural adaptation:
- Have many mitochondria; provide energy to absorb more mineral salts through active transport
- The root hairs increase the surface area; maximising the absorption
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Function: Absorb water and dissolved mineral salts in the ground |
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Guard cell
Structural adaptation:
- Have chloroplasts; produce glucose
- Have a large vacuole; control the osmotic pressure of the cell; aid in controlling the opening and closing of the stoma
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Function: Control the opening and closing of the stoma |