cell biology - surface area to volume ratio

Question 1

how do you work out the surface area?

Answer 1

width x height x number of sides

Question 2

how do you work out the volume?

Answer 2

width x height x base

Question 3

As organisms get larger, what happens to their surface area to volume ratio? who is this a problem for and why?

Answer 3

falls sharply
for multicellular organisms as surface area is not large enough for the volume. the cells on the surface can get enough oxygen by diffusion but not enough oxygen diffuses into the cells in the centre of the organism as it is too far from the surface

Question 4

how have animals adapted to the problem of not enough oxygen diffusion to cells in the centre?

Answer 4

• special structures for gas exchange with very high surface area e.g lungs
• have transport system for gases around the body

Question 5

how do fish get oxygen?

Answer 5

oxygen-rich water passes into the mouth. flows over the gills where oxygen is transported to the bloodstream

Question 6

how do fish get oxygen?

Answer 6

oxygen-rich water passes into the mouth. flows over the gills where oxygen is transported to the bloodstream

Question 7

what are the gills covered in? function?

Answer 7

fine filaments where gases pass in and out of the blood

Question 8

cycle of blood in fish

Answer 8

deoxygenated blood passes into the filaments. oxygenated blood diffuses from water into the blood. oxygen returns to the body

Question 9

how are filaments adapted to make diffusion as efficient as possible?

Answer 9

• massive surface area
• thin membrane (short diffusion pathway)
• efficient blood supply to take oxygenated blood away. ensures concentration gradient always high