surface area to volume ratio

Question 1

what are amoeba?

Name a key feature on amoeba.

Answer 1

they are single celled organisms.

they have a huge surface area for their volume. This is the surface area : volume ratio

Question 2

what do single celled organisms such as omoeba rely on to transport molecules in and out of the cell

Answer 2

they rely on diffusion

Question 3

how can diffusion benefit single celled organisms? give an example for this.

Answer 3

amoeba is a single celled organism that uses diffusion to transport molecules in and out of its cell

Question 4

where does all of the oxygen needed for a cell diffuse into?

Answer 4

into/ through the cell membrane

Question 5

calculating surface area : volume

calculate surface area of a cube with side length of 1mm

Answer 5

surface area of each side = 1mm x 1mm = 1mm^2
 1mm^2 x number of sides= 6
1mm^2 x 6 = 6mm^2
total surface area = 6mm^2
volume = 1mm x 1mm x 1mm = 1mm^3

surface area : volume
6:1

Question 6

calculate the surface area : volume

cube with a side length of 2mm

Answer 6

3 : 1

surface area of each side = 2mm x 2mm= 4mm^2
surface area of each side x number of sides=
4mm^2 x 6 = 24mm^2

volume = 2mm x 2mm x 2mm = 8mm^3

surface area : volume
24:8
3 : 1

Question 7

calculate the surface area : volume when a cube has a side length of 3mm

Answer 7

length of each side = 3mm x 3mm = 9mm^2
9mm^2 x number of sides (6) = 54mm^2

volume = 3mm x 3mm x 3mm = 27mm^3

surface area : volume=
54 : 27
2 : 1

Question 8

what happens to the surface area : volume ratio as organisms get larger?

Answer 8

as organisms get larger, the surface area : volume ratio falls sharply.

Question 9

why is organisms getting larger and the surface area : volume ratio falling sharply a problem to multicellular organisms?

Answer 9

this is a problem for multicellular organisms because their surface area is not large enough for their volume
cells on the surface can get enough oxygen simply by diffusion however not enough oxygen can diffuse into the cells in the centre of the organism. they are too far away from the surface

Question 10

cells on the _______ get enough oxygen by diffusion and cells found in the ________ don’t have enough oxygen diffusing into the cell.
why is this?

Answer 10

cells on the surface can get enough oxygen simply by diffusion however not enough oxygen can diffuse into the cells in the centre of the organism.
this is because they are too far away from the surface

Question 11

where do fish get their oxygen?

Answer 11

from the oxygen enriched water that passes into the mouth off the fish and then flows over the gills, where the oxygen is transported into the bloodstream

Question 12

in a fish, where is the oxygen flowing past the gills go to?

Answer 12

it gets transported into the bloodstream.

Question 13

what are the gills covered in?

Answer 13

a lot of fine filaments

Question 14

what is the function of the gills filaments?

Answer 14

this is where gases pass in and out of the blood

Question 15

what else passes through into the filament?

Answer 15

deoxygenated blood passes into the filament.

Question 16

where does the oxygen diffuse from and where to in a fish?

Answer 16

oxygen diffuses from the water into the blood.

Question 17

where does oxygenated blood go?

Answer 17

cells on the surface can get enough oxygen simply by diffusion however not enough oxygen can diffuse into the cells in the centre of the organism. they are too far away from the surface

Question 18

Name the 3 adaptations that the filaments have to increase the rate and efficiency of diffusion.

Answer 18

• the filaments gives the gills a massive surface area
• have a thin membrane to provide a short diffusion pathway
• efficient blood supply to take take the oxygenated blood away.(ensures the concentration gradient is always high)

Question 19

what does the efficient blood supply do in a fish

Answer 19

takes the oxygenated blood away in order to ensure that the concentration gradient is always high