BIOLOGY · Stage 7 · Chapter 2: Cells and Organisation
Biology 2.5 Specialised animal cells — Structure and Adaptation — Alhussan International Academy - Biology (Stages 7-9) Revision Notes & Topical Questions
5 min read 6 parts Lesson 5 of 10
Lesson summary
2.5 Specialised animal cells — Structure and Adaptation — Alhussan International Academy — Biology (Stages 7–9) notes: Link the structure of specialised animal cells to their functions and explain how each is adapted.Single-celled organisms — one cell carries out all the processe…
- Multicellular organisms
- Specialised cell
- Differentiation
- Numbers and size
- Adaptations
- Energy demand
Section 1 of 6Many cells, many jobs
- Single-celled organisms
- one cell carries out all the processes of life.
- Multicellular organisms
- they are made of more than one cell, often millions or billions of cells.
- Specialised cell = a cell whose structure is adapted to carry out a particular function in the body.
- Cells in a multicellular organism are not all the same.
- Differentiation
- as a cell develops it changes shape and builds the structures needed for its function.
- Benefit
- specialised cells working together let a multicellular organism do many jobs at once, grow larger and become more complex.
- The cost is that specialised cells depend on other cells for what they cannot do themselves.
Section 2 of 6Red blood cells
- Function
- they carry oxygen around the body.
- Plasma
- blood is a yellow liquid called plasma full of cells, and red blood cells make it look red.
- Numbers and size
- more than half the cells in the body are red blood cells, and they are the smallest, with an average diameter of 7 µm.
- Adaptations
- They are filled with haemoglobin, a red substance that carries oxygen and gives them their colour.
- They are small and flexible, so they pass through tiny blood vessels.
- They have no nucleus, so there is more space for haemoglobin, although they do not live very long.
- They are biconcave with a dimple on both sides, giving a big surface area to pick up oxygen.
Section 3 of 6Neurones (nerve cells)
1Function3 points
- they carry electrical messages around the body in long extensions called axons.
- Some carry information about the surroundings to the brain.
- Others carry instructions from the brain to parts of the body such as muscles.
2Adaptations3 points
- They are long, and axons can be 1 m or longer, to carry messages around the body.
- They have branches to connect to other neurones.
- They have insulation so electrical messages travel faster.
Section 4 of 6Ciliated cells
- Function
- they move mucus, dust and bacteria away from the lungs in the airways.
- Adaptations
- They are covered with tiny hair-like cilia that beat to cause movement.
- They contain many mitochondria to supply the energy needed to move the cilia.
Section 5 of 6Other specialised animal cells
| Cell | Function | Adaptations |
|---|---|---|
| Muscle cell | Contracts to cause movement | Protein fibres that slide to shorten the cell; many mitochondria for energy |
| Sperm cell | Fertilises the egg | Tail to swim; streamlined head; many mitochondria; enzymes in the head to enter the egg |
| Egg cell (ovum) | Is fertilised and begins the embryo | Large size with a food store in the cytoplasm; membrane changes after fertilisation to stop other sperm entering |
Section 6 of 6Linking structure to function
- Energy demand
- cells that need much energy, such as muscle, sperm and ciliated cells, have many mitochondria.
- Protein making
- a cell making much protein has many ribosomes.
- Length
- a nerve cell is long because it reaches from one part of the body to another.
- Absorption
- a cell lining the small intestine has microvilli, finger-like projections that increase surface area for absorbing digested food.
- Same genes
- specialised cells in one organism have the same genes and differ in the structures they build.
Last updated: