6.2 gas exchange in single-celled organisms & insects

Question 1

explain how single-cell organisms carry out gas exchange.

Answer 1

oxygen is absorbed by diffusion through cell-surface membrane as they have a large SA:V ratio

Question 2

what is the disadvantage for the high surface area in insects?

Answer 2

faster water evaporation

Question 3

what internal network is used for gas exchange in insects?

Answer 3

trachae

Question 4

what features does the exchange system in insects have? how does it benefit?

Answer 4

• supported by strengthened rings to prevent collapsing
• divides into smaller tracheoles
  therefore atmoshperic air is brought to respiring tissues through a short diffusion pathway

Question 5

how does respiratory gases move in through a diffusion gradient in insects?

Answer 5

• oxygen concentration (used up during respiration) decreases towards ends of tracheoles
• lower diffusion gradient causes oxygen to diffuse from atmosphere to cells

Question 6

how does respiratory gases move in through mass transport?

Answer 6

abdominal pumping squeezes trachea and enable mass movement of air in & out

Question 7

how does respiratory gases move in using fluids at the ends of tracheoles?

Answer 7

• muscle cells carry out anaerobic respiration during major activity, which produces lactase
• this lowers the water potential and therefore water moves to muscle cells through osmosis
• the lower volume of water draws air into them

Question 8

explain how gases enter and leave the cell in insects.

Answer 8

through spiracles;
open for gas exchange & closed to prevent water loss