Gas Exchange

Question 1

What is the name of the surface where gas exchange takes place?

Answer 1

The respiratory surface

Question 2

What is Gas exchange?

Answer 2

The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and its environment.

Question 3

What are the essential features for Gas exchange?

Answer 3

Large Surface area
Thin (short diffusion distance)
Permeable
Steep diffusion gradient

Question 4

Unicellular organisms eg Amobea

Answer 4

Large SA:V ratio
Thin cell membrane (single cell)

They can therefore absorb enough oxygen across the cell membrane to meet their needs
Remove CO2 fast enough to prevent building up a high concentration, making the cytoplasm to acidic for the enzymes to function.

Question 5

Multicellular Organisms - Flatworms

Answer 5

Aquatic organisms
They have a large SA and therefor SA:V ratio
short diffusion pathway

Question 6

Multicellular Organisms - Earthworms

Answer 6

Cylindrical so SA: V ratio is smaller than a Flatworms
Its skin in the respiratory surface, which it keeps moist by secreting mucus.
It is slow moving and has a slow metabolic rate so has a low oxygen requirement –> enough O2 diffuses across the skin to meet the requirements
Haemoglobin is present in the blood which carries the O2 away for the skin –> maintains conc gradient
CO2 is also carried in the blood which diffuses out via the skin

Question 7

Multicellular vs Unicellular

Answer 7

Multicellular have a higher metabolic rate, they need t deliver more O2 to cells and remove more CO2
With an increase in size and specialisation of cell, tissues and organs they are more interdependent,
They must actively maintain a steep concentration gradient across the respiratory surface –> can do this by moving the environmental medium eg water/air
Respiratory surfaces must be thin to make the diffusion pathway short and protected from damage