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Cells


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cells


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Cells

Made up of:

-protoplasm
- cellulose cell wall (non-living and only in plants)

Protoplasm consists of:

- nucleus which controls cellular activities and consists of
    - nuclear envelope
    - nucleoplasm
    - chromatin (made up of DNA)
    - nucleolus

- cytoplasm which surrounds the nucleus and where most life processes occur and consists of
    - mitochondria - sites of energy release
    - vacuoles - contain water and food substances
    - chloroplasts - in plant cells only
    - centrioles -  in animal cells

- cell surface membrane which is the partially permeable, outer covering enclosing the cytoplasm

Plant and Animal cells

Both plant and animal cells have
- nucleus
- cytoplasm
- cell membrane
- mitochondria - energy is released here by respiration

Only plant cells have
- cell wall
- large vacuole
- chloroplasts

Specialised cells

1. Root hair cell in plants is adapted to do its job of taking in water and nutrients by having

- a large surface area
- a thin cell membrane

2. Red blood cell which carries oxygen around the body have

- no nucleus and a large surface area (concave shape) - allows maximum area for oxygen carriers
- have haemoglobin to carry oxygen

3. White blood cell which fights disease and some make antibodies - their adaptations:

- irregular shape and they can change shape to squeeze out of blood vessels and get to the site of infection
- others have cytoplasm which can flow making it possible for the cell to change shape and hence surround and engulf bacteria

Cells, tissues, organs and systems

Tissue: a group of cells make up a tissue
eg heart muscle tissue

Organ: a group of tissue makes up an organ
eg heart

System: a group of organs makes up a system
eg circulatory system

Organism: a group of systems make up an organism
eg Humans
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