5.1.1 the need for communication systems

Question 1

cell signalling

Answer 1

the way in which cells communicate with each other

Question 2

conditions enzymes require

Answer 2

• suitable temperature
• suitable pH
• aqueous environment which keeps substrates & products in solution
• freedom from toxins & excess inhibitors

Question 3

what is the environmental change

Answer 3

stimulus

Question 4

what is the way in which an organism changes its behaviour/physiology in response to a stimulus

Answer 4

response

Question 5

example of cells responding to their changing internal environment

Answer 5

• the accumulation of excess waste/toxins acts as a stimulus to cause removal of waste products so cell can survive
• build up of waste products in tissue fluid may act directly on cells, which respond by reducing their activities so less waste is produced

Question 6

what is composition of tissue fluid maintained by

Answer 6

blood

Question 7

explain how the blood maintains the internal environment

Answer 7

• waste/toxins accumulating in tissue fluid enter blood & carried away
• must be removed from body by excretion
• concentrations of waste products/substances in blood closely monitored

Question 8

why is a multicellular organism more efficient than a single-celled organism

Answer 8

cells are differentiated = specialised for different functions

Question 9

what will a good communication system do?

Answer 9

• cover whole body
• enable cells to communicate with one another
• enable specific communication
• enable rapid communication
• enable short-term/long-term responses

Question 10

how does cell signalling work

Answer 10

1. one cell releases a chemical that’s detected by another cell
2. second cell responds to signal from first cell

Question 11

2 major systems of communication that work by cell signalling

Answer 11

1. neuronal system
2. hormonal system

Question 12

explain how the neuronal system works

Answer 12

• interconnected network of neurones which signal to each other across synapse junctions
• neurones can conduct signal fast & enable rapid responses to stimuli which may change quickly

Question 13

explain how the hormonal system works

Answer 13

• system which uses blood to transport signals
• cells in an endocrine gland release signal (hormone) into blood
• hormone transported through body but only recognised by specific target cells
• system enables longer-term responses to be coordinated