Exchange systems

Question 1

How do single-celled organisms carry out substance exchange?

Answer 1

Substances diffuse directly into and out of cell across the cell membrane. Short diffusion pathway so diffusion rate quick

Question 2

How do gases diffuse into insects?

Answer 2

Through small openings in their chitin exoskeleton called spiracles

Question 3

What do spiracles lead to and what is that thing’s structure & function?

Answer 3

Spiracles lead to tracheae. The Walls of these tracheae are enforced with spirals of chitin which prevent it from collapsing.

Question 4

What do tracheae extend into and what is that thing’s structure&function?

Answer 4

Tracheoles - one cell thick - provides short diffusion distance for gases.
Huge number of tracheoles provides large surface for area diffusion

Question 5

What is the use of tracheal fluid in the tracheoles?

Answer 5

When lactic acid is formed (which lowers water potential of cells), water from tracheal fluid moves into cells. This reduces volume of tracheal fluid, drawing air into tracheoles.it also means more tracheal surface is available for gas exchange