diffusion DEFINITELY IN EXAM

Question 1

define diffusion

Answer 1

the net movement of particles from an area of high to low concentration
(spreading out of particles)

Question 2

what do cells need oxygen for? and what subcellular structure carries out that process?

Answer 2

cells need oxygen for respiration which is carried out by the mitochondria

Question 3

what is oxygen transported in? and what is this for?

Answer 3

oxygen is transported in the bloodstream from the lungs which causes cells to be surrounded by a high concentration of oxygen

Question 4

explain how gases enter/leave the cell

Answer 4

cells are surrounded by high concentrations of oxygen. Oxygen is transported in the bloodstream from the lungs
oxygen molecules move into the cells by diffusion from an area of high to low concentration
the oxygen is then used to generate energy in respiration and this produces the waste gas carbon dioxide
this means we have a higher concentration of carbon dioxide inside the cell than outside
so the carbon dioxide moves out of the cell by diffusion

Question 5

what is urea? where does it come from? after it diffuses out of cells where does it go?

Answer 5

urea is a waste products which is produced inside of cells. It diffuses out of the cells into the blood plasma and is excreted by the kidneys

Question 6

what 4 factors affect the rate of diffusion

Answer 6

• concentration gradient
  (the greater the concentration gradient the faster that diffusion takes place)
• temperature
  (the higher the temperature the greater the rate of diffusion as the particles have more kinetic energy so are moving faster and collide with each other more)
• surface area of the membrane
  ( the larger the surface area of the cell membrane the greater the rate of diffusion)
• diffusion distance

Question 7

how to figure out surface area to volume ratio

Answer 7

figure out volume and surface area

for a cube

• volume = base x height x depth
• surface area = base x height x the number of sides (6)