6.2 gas exchange in single-celled organisms and insects

Question 1

describe how single celled organisms exchange gases

Answer 1

they’re small so have a large SA:Vol
this is sufficient to exchange the substances required

Question 2

Parts an insect uses to exchanges gases

Answer 2

spiracles
tracheae
tracheoles

Question 3

3 ways that insects exchange gases

Answer 3

1. diffusion gradient
2. mass transport
3. water in tracheoles

Question 4

how does the diffusion gradient work with exchanging gases in insects?

Answer 4

• respiration in cells uses O2
• decreasing the concentration at the ends of the tracheoles
• producing a conc grad, causing O2 to diffuse from the atmosphere
• vice versa with CO2

Question 5

how does mass transport work with exchanging gases in insects?

Answer 5

• contraction of muscles squeezes the trachea
• enables mass movement of air

Question 6

how does water in tracheoles work with exchanging gases in insects?

Answer 6

• intense activity = anaerobic respiration
• anaerobic respiration = lactic acid
• increase in lactic acid = decrease in water potential inside the cells
• water moves from the tracheoles into the cells by osmosis
• lowers vol of water in tracheoles = draws air in
• allows air to diffuse in gas phase rather than in liquid phase

Question 7

What are spiracles?

Answer 7

spiracles - pores on the surface leading to tracheae

Question 8

What is the trachea in insects?

Answer 8

tracheae - internal network of tubes supported by strengthened rings to prevent collapse

Question 9

What are tracheoles in insects?

Answer 9

tracheoles - smaller dead end tubes branching from tracheae, they extend directly to respiring tissue, providing a short diffusion pathway from air to cells