3.3.2.1 Gas Exchange - Micro-organisms and Insects

Question 1

Why do single-celled organisms rely on diffusion for gas exchange?

Answer 1

They have a large surface area to volume ratio, allowing efficient diffusion across their body surface.

Question 2

How do single-celled organisms exchange gases?

Answer 2

Oxygen and carbon dioxide diffuse across their cell surface membrane without the need for specialized transport systems.

Question 3

How does a cell wall affect gas exchange in single-celled organisms?

Answer 3

It does not act as a significant barrier, allowing gases to diffuse freely across the membrane.

Question 4

What are the insects SA:Vol ratio?

Answer 4

They have a high ratio meaning a high diffusion rate

Question 5

What stops proper gas excahnge in insects?

Answer 5

The insects exoskeleton makes it hard for direct gas exchange
Therefore insects have a tracheal system

Question 6

What are the three main parts of the tracheal system?

Answer 6

Spiracle - Surface of the exoskeleton
Tracheae - Main network of tubes and stops from collapsing by strenghtened rings
Tracheoles - Secondary tubes that stem off the Tracheae and lead to dead ends which are fluid-filled

Question 7

What are the three main ways insects respire?

Answer 7

Along a diffusion gradient
Mass Transport
The ends of the tracheoles are filled with tracheal fluid (water)

Question 8

How do insects respire using a concentration gradient?

Answer 8

• Oxygen is used up near the ends of the tracheoles creating a concentration gradient so oxygen from outside move in
• Carbon Dioxide produced during repiration creates a diffusion gradient in the opposite direction causing CO2 to move out the insect

Question 9

How do insects respire using mass transport?

Answer 9

• The contraction of muscles in insects can squeeeze the trachea moving air in and out
• Further speeds up gas exchange

Question 10

What is produced during insects heavy acitivity?

Answer 10

Lactate
Lactate is soluble and lowers the water potential