The need for communication systems

Question 1

Define cell signalling

Answer 1

The way in which cells communicate with each other.

Question 2

What are the conditions that all living things need to maintain inside their cells

Answer 2

• a suitable temperature
• a suitable pH
• an aqueous environment that keeps the substrates and products in solution
• freedom from toxins and excess inhibitors

Question 3

What happens if these conditions are not maintained?

Answer 3

The cells will become inactive and die.

Question 4

Why must cells be able to communicate and coordinate their activities?

Answer 4

Because cells are specialised to rely on each other.

Question 5

What do all living organisms environment consist of?

Answer 5

Air, water or soil.

Question 6

What happens when the external environment changes?

Answer 6

It places stress on the living organism.
e.g. cooler environment will cause greater heat loss, if organism is to remain active and survive , the changed in the environment must be monitored and the organism must change its behaviour or physiology to reduce stress.

Question 7

What is the environmental change

Answer 7

The stimulus

Question 8

What is the way in which the organism changes its behaviour or physiology

Answer 8

The response

Question 9

If environment changes slowly…

Answer 9

These changes elicit a gradual response.
e.g. artic fox has thicker white coat- winter and thinner brown coat in summer.
Winter- great insulation and camouflage
summer- does not overheat and camouflage

Question 10

If environment changes quickly… e.g. appearance of predator

Answer 10

stimulus must be monitored and organism must respond to change.

Question 11

Why are most of the cells and tissues not exposed to the external environment.

Answer 11

As they are protected by epithelial tissues and organs- bark and skin.

Question 12

What is the environment of internal cells

Answer 12

tissue fluid

Question 13

What happens to the substances formed in metabolic activities that are unwanted or toxic?

Answer 13

They move out of the cells and into the tissue fluid.
So, the activities of the cells alter their own environment.

Question 14

What is carbon dioxide and what happens if it is allowed to build up in the tissue fluid outside the cells?

Answer 14

Carbon dioxide- waste product
It will alter the pH of the tissue fluid and could disrupt the action of enzymes and other proteins.

Question 15

Why does the accumulation of excess waste or toxins in this internal environment act as a stimulus?

Answer 15

It causes the removal of the waste products so the cells can survive.

Question 16

How does the build up of waste products in the tissue fluid act directly on cells?

Answer 16

The cells respond by reducing their activities so less waste product is produced.

Question 17

What is tissue fluid maintained by?

Answer 17

The blood.

Question 18

An wastes or toxins accumulating in the tissue fluid are likely to enter the blood and be carried away which means…

Answer 18

To prevent their accumulation in the blood they must be removed from the body by excretion.

Question 19

Why is a multicellular organism more efficient than a single celled?

Answer 19

It’s cells are differentiated, so cells are specialised to perform particular functions.

Question 20

What is required to ensure that different parts of the body work together effectively?

Answer 20

A good communication system.

Question 21

What does a good communication system maintain?

Answer 21

• covers the whole body
• enables cells to communicate with each other
• enable specific communication
• enable rapid communication
• enable short-term and long-term responses.

Question 22

2 major systems that work by cell signalling:

Answer 22

• neuronal communication
• hormonal communication

Question 23

Neuronal communication

Answer 23

interconnected network of neurones that signal to each other across a synapse. The neurones can conduct a signal very quickly and enable rapid responses to stimuli that may be changing rapidly.

Question 24

Hormonal communication

Answer 24

Uses blood to transport its signals. Cells in endocrine organ release the signal directly into the blood. The hormone is transported throughout the body but is only recognised by specific target cells. It enables longer term responses to be coordinated.