diffusion

Question 1

what is diffusion

Answer 1

the net movement of particles from an area of high concentration to an area of low concentration

Question 2

why can molecules in liquid and gas states diffuse

Answer 2

they are constantly moving and bumping into each other - they tend to spread out

Question 3

why can molecules in liquid and gas states diffuse

Answer 3

they are constantly moving and bumping into each other - they tend to spread out

Question 4

why is diffusion important

Answer 4

all living cells rely on diffusion to survive. dissolved substances have to pass through the cell membrane to get in or out

living cells use it for:
- getting raw materials for respiration (dissolved substances + gasses)
- removing waste products (eg. from respiration)
- plants use it for photosynthesis (raw materials in, waste products out)

Question 5

diffusion in unicellular organisms:

Answer 5

nutrients and oxygen can diffuse directly into the cell + waste products can diffuse directly out

diffusion occurs at a fast enough rate to supply the whole cell

Question 6

diffusion in multicellular organisms:

Answer 6

have a small surface area:volume

diffusion can’t occur quickly enough to sustain them

require an organ system with specialised adaptations to supply all their cells with nutrients and oxygen (through diffusion) and collect waste (through diffusion)

Question 7

practical: investigate diffusion

Answer 7

1) get 3 stained agar jelly cubes (0.5x0.5x0.5, 1x1x1, 2x2x2)
2) half fill a beaker with 1% vitamins C solution
3) add all the cubes to the solution at the same time and leave for 20 mins
4) after 20 mins remove them and see how long it takes for them to go colourless

Question 8

diffusion is fastest when:

Answer 8

• high concentration gradient
• high temperature
• short, thin membrane
• large surface area:volume ratio
• short distance