6.4 The Organisation And Specialisation Of Cells

Question 1

Define differentiated cells

Answer 1

Cells that are specialised to carry out very specific functions

Question 2

3 examples of specialised animals cells

Answer 2

Erythrocytes, neutrophils and sperm cells

Question 3

How are erythrocytes specialised to carry out their function?

Answer 3

• have a flattened biconcave shape which increases their surface area to volume ratio, essential for their of transporting oxygen around the body
• do not have nuclei, increases space available for haemoglobin
• they are flexible so that they are able to squeeze through narrow capillaries

Question 4

How are neutrophils specialised to carry out their function?

Answer 4

• they have a multi-lobed nucleus which makes it easier for them to squeeze through gaps to get to site of infections
• they have a granular cytoplasm which contains many lysosomes that contain enzymes used to attack pathogen

Question 5

How are sperm cells specialised to carry out their function?

Answer 5

• sperm have a tail/flagellum so they can move
• they contain many mitochondria to supply the energy needed to swim
• the acrosome on the head of the sperm contains digestive enzymes which breakdown protective layers around ovum to allow sperm to penetrate for fertilisation

Question 6

3 examples of specialised plant cells

Answer 6

Palisade cells, root hair cells, guard cells

Question 7

How are palisade cells specialised to carry out their function?

Answer 7

• contain chloroplasts to absorb large amount of light for photosynthesis, chloroplasts can move within the cytoplasm in order to absorb more light
• the cells are rectangular so they can be packed closely together to form a continuous layer
• they have thin cell walls, increasing rate of diffusion of carbon dioxide
• they have a large vacuole to maintain turgor pressure

Question 8

How are root hair cells specialised to carry out their function?

Answer 8

• they have long extensions (root hairs) which increase the surface area of the cell
  This maximises the uptake of water and minerals from the soil
• root hairs have a thin cellulose cell wall, and inside the root hairs have a lower water potential increases rate of osmosis

Question 9

How are guard cells specialised to carry out their functions?

Answer 9

• when they lose water they change shape to close stoma to prevent further water loss
• the cell wall of a guard cell is thicker on one side so the cell is thicker on one side so the cell does not change shape symmetrically as its volume changes

Question 10

Define tissue

What are the four main categories of tissues in animals?

Answer 10

A tissue is made up of a collection of differentiated cells that have specialised function.
4 main categories of tissues in animals:
- nervous tissue 
- epithelial tissue 
- muscle tissue   
- connective tissue

Question 11

How is squamous epithelium specialised?

Answer 11

• made up of squamous epithelial cells that are flat

- very thin, once cell thick which allows for rapid diffusion across a surface (e.g. lining of lungs)

Question 12

How is ciliated epithelium specialised?

Answer 12

• made of ciliated epithelial cells

- these cells have ‘hair like’ structures (cilia) that move

Question 13

How is cartilage specialised?

Answer 13

• its a connective tissue
• contains elastin and collagen
• its firm and flexible tissue

Question 14

How is muscle specialised?

Answer 14

• muscle fibres that contain contractile proteins so that a muscle can contract in order to move bones

Question 15

Two types of tissues in plants?

Answer 15

• epidermis tissue (adapted to cover plant surfaces)

- vascular tissue (adapted for transport of water and nutrients)

Question 16

How is the epidermis specialised?

Answer 16

• single layer of closely packed cells covering surfaces of plants
• usually covered by waxy waterproof cuticle to reduce water loss
• stomata are present in epidermis to allow carbon dioxide, water vapour and oxygen in and out

Question 17

How is xylem tissue specialised?

Answer 17

• vascular tissue responsible for transport of water and minerals through plants
• composed of elongated dead cells
• strengthened by lignin which provides structural support for plants

Question 18

How is phloem tissue specialised?

Answer 18

• vascular tissue responsible for the transport of organic nutrients e.g. sucrose
• composed of sieve tube elects separated by sieve plates

Question 19

Define an organ

Answer 19

A collection of tissues that are adapted to perform a particular function in an organism

Question 20

Define organ system

E.g.?

Answer 20

Organ systems are composed of a number of organs that work together to carry out a major function
E.g. digestive system, gaseous exchange system, cardiovascular system