The importance of exchange surfaces and transport systems in humans | Exit Quiz | Oak National Academy

Which factors does the surface area and volume affect?

• rate of diffusion

• diffusion distance

• which substances can diffuse in and out of a cell

Answer explanation

Which substances can enter and leave a cell is determined by a combination of molecule size, its properties, and the cell membrane, not the surface area or volume.

True or false? Large living organisms have a large surface area to volume ratio.

• true

• false

Answer explanation

An elephant has a smaller surface area to volume ratio than a mouse. Large living organisms have a small surface area to volume ratio.

Why is a small surface area a disadvantage to organisms?

• Decreasing SA : V decreases diffusion rate.

• Decreasing SA : V increases diffusion rate.

Answer explanation

A smaller surface area to volume ratio results in a lower diffusion rate and cells may not get what they need to survive quick enough.

Having many villi {{}} the surface area over which diffusion can take place.

• increases

• decreases

• does not impact

Answer explanation

The shape of the villi and the number of them creates a very large surface area over which diffusion can take place.

What are the advantages of a circulatory system?

• It means substances don't have to diffuse.

• It moves nutrients and waste products around the body.

• It reduces the time taken for substances to diffuse from the blood to the cells.

• It brings blood near to the surface of cells which reduces diffusion distance.

• It means active transport will occur instead of diffusion.

Answer explanation

Substances that are transported in the blood still need to diffuse into cells, but they are bought into close contact with the body cells and only have a short distance to diffuse.

How are the alveoli adapted for efficient diffusion?

• good blood supply

• large surface area

• thin cells

• thick cells

• small surface area

Answer explanation

Thick cells would mean a large diffusion distance which would slow down diffusion. A small surface area would mean less diffusion could take place.