Single Cell and Insects- Gas Flashcards
Single-celled organisms are small, what does this mean for their SA:V?
They have a large SA:V.
In single-celled organisms how does gas exchange take place?
Oxygen is absorbed by diffusion across the body surface (cell surface membrane). Carbon dioxide diffuses out.
What are tracheae?
An internal network of tubes, supported by strengthened rings to prevent collapse.
What do tracheae divide into?
Smaller dead-end tubes called tracheoles. They extend throughout the body tissue of the insect, their ends are filled with fluid.
Name the 3 processes involved in gas exchange of insects.
- Diffusion of of gases along a diffusion gradient
- Mass transport
- The ends of tracheoles filled with water.
Describe the gas exchange that occurs along a diffusion gradient in an insect.
Oxygen is used up in respiration so its concentration towards the end of the tracheoles decreases. This causes oxygen to diffuse along to the cells. CO2 is produced in respiration which creates a concentration in the opposite direction.
How does gas exchange occur via mass transport in insects?
Insects can contract muscles that cause the trachea enabling mass movements. This speeds up the process.
Anaerobic respiration and the water filled tracheole ends.
Lactate is produced which is soluble and so lowers the water potential of cells. water moves from the tracheoles into cells by osmosis. This decreases their volume which draws more gas into them, meaning the final stage is gaseous and not through water which would be slower.
What are spiracles?
Tiny pores on the body surface controlled by valves so they can be opened and closed to limit water loss.
What are the limitations of the insect gaseous exchange?
Relies on diffusion, for efficient exchange diffusion paths must be kept short so this limits the size they can attain.
