1.2 Specialised cells and their functions

Question 1

What are specialised cells?

Answer 1

Cells that have a specific structure to allow them to do their specific function

Question 2

How do cells specialise?

Answer 2

By undergoing differentiation

Question 3

Examples of specialised cells in animals

Answer 3

• Sperm cells
• Egg cells
• Ciliated epithelial cells

Question 4

Why have sperm cells specialised?

Answer 4

To carry the male’s DNA to the egg cell (ovum) for successful reproduction

Question 5

How have sperm cells specialised?

Answer 5

• Acrosome (tip of head): contain enzymes that break down the eggs jelly coat so that the sperm nucleus can enter the egg for fertilisation.
• Haploid nucleus: contains only one copy of each chromosome
• Mitochondria (lots in middle piece): the site of respiration, allows sperm to have enough energy to swim to the egg cell
• Tail: waves from side to side allowing sperm to
  swim to the egg cell

Question 6

Why have egg cells specialised?

Answer 6

To accept a single sperm cell and develop into an embryo

Question 7

How have egg cells specialised?

Answer 7

• Packed with nutrients in cytoplasm: to supply the fertilised egg with energy and raw materials for growth
• Haploid nucleus: contains only one copy of each chromosome
• Jelly coat (protects egg cell): hardens after fertilisation so only one sperm enters the egg

Question 8

Why have ciliated epithelial cells specialised?

Answer 8

To pass bacteria (trapped by mucus) to the stomach

Question 9

How have ciliated eipithelial cells specialised?

Answer 9

• Cilia: Hair like extensions to the cell that pass bacteria to and fro to move substances along.
• Found in the lining of the oviducts: to pass the egg / embryo to the uterus
• Found in the upper respiratory tract: to pass dust and particles out of the trachea
• Diploid: contains two sets of chromosomes

Question 10

Examples of specialised cells in animals

Answer 10

• Root hair cells
• Xylem cells
• Phloem cells

Question 11

Why have root hair cells specialised?

Answer 11

To take up water by osmosis and mineral ions by active transport from the soil as they are found in the tip of roots

Question 12

How have root hair cells specialised?

Answer 12

• Large surface area (due to root hairs): more water can move in
• Large permanent vacuole: affects the speed of movement from the soil to the cell
• Lots of mitochondria: to provide energy from respiration for the active transport of mineral ions into the root hair cell.

Question 13

Why have xylem cells specialised?

Answer 13

To transport water and mineral ions up the plant from the roots to the shoots

Question 14

How have xylem cells specialised?

Answer 14

• Lignin is deposited (in spirals which helps the cells withstand the pressure from movement of water) which causes the cells to die. They become hollow and are joined end-to-end to form a continuous tube so water and mineral ions can move through

Question 15

Why have phloem cells specialised?

Answer 15

To carry the products of photosynthesis (food) to all parts of the plants

Question 16

How have phloem cells specialised?

Answer 16

• Cell walls: of each cell forms structures called sieve plates when they break down, allowing the movement of substances from cell to cell.
• Despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of the companion cells