movement of substances

Question 1

2.15 definition of diffusion

Answer 1

the random movement of particles from an area of higher concentration to an area of lower concentration

Question 2

2.15 definition of osmosis

Answer 2

the net diffusion of free water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane

Question 3

2.15 osmosis in cell:
what is: solution outside cell has same water potential as inside cell - no net movement

Answer 3

isotonic solution

(animal = normal)
(plant = flaccid)

Question 4

2.15 osmosis in cell:
what is: solution outside cell has higher water potential then inside cell - net movement of free water molecules into cell

Answer 4

hypotonic solution

(animal = lysed)
(plant = turgid)

Question 5

2.15 osmosis in cell:
what is: solution outside cell has lower water potential then inside cell - net movement of free water molecules out of cell

Answer 5

hypertonic solution

(animal = shrivelled)
(plant = plasmolysed)

Question 6

2.15 definition of active transport

Answer 6

movement of molecules from an area of low concentration to an area of high concentration using ATP

Question 7

2.16 the four main factors that affect the rate of movement

Answer 7

surface area to volume ratio, distance, temperature and concentration gradient

Question 8

2.16 why is a larger surface area a good thing

Answer 8

it quickens the rate at which substances can move across its surface

Question 9

2.16 example of large surface area

Answer 9

highly folded surface of the small intestine increases its surface area

Question 10

2.16 why is a shorter distance a good thing

Answer 10

the smaller the distance molecules have to travel, the faster the transport will occur

Question 11

2.16 example of short diffusion distance

Answer 11

alveoli walls are one cell thick - rate of diffusion across them is as fast as possible

Question 12

2.16 why is higher temperature a good thing

Answer 12

the higher the temperature, the faster molecules move as they have more energy

Question 13

2.16 how is higher temp a good thing

Answer 13

because there are more collisions against the cell membrane and therefore a faster rate of movement across them

Question 14

2.16 why is a greater difference in a concentration gradient a good thing

Answer 14

the greater the difference in concentration on either side of the membrane, the faster movement across it will occur

Question 15

2.16 how is a greater difference in a concentration gradient a good thing

Answer 15

because the on the side with the higher concentration, more random collisions against the membrane will occur

Question 16

2.17 practical: investigating diffusion

Answer 16

coloured agar is made from indicators
coloured agar is cut into required dimensions
calculate the surface area, SA:V R and volume and record it
cubes placed in boiling tubes of different solutions (same volume of it)
^^^ e.g. dilute hydrochloric acid
measurements taken of time for cube to completely change colour of indicator
can draw a graph of rate of diffusion (rate of colour change) changes with surface area : volume ratio of agar cubes

Question 17

2.17 practical: investigating osmosis

Answer 17

prepare a range of sucrose (sugar) solutions ranging from 0 Mol/dm3 (distilled water) to 1 mol/dm3
set up 6 labelled test tubes with 10cm3 of each of the sucrose solutions
using the knife, cork borer and ruler, cut 6 equally-sized cylinders of potato
blot each one with a paper towel and weigh on the balance
put 1 piece into each concentration of sucrose solution
after 4 hours, remove them, blot with paper towels and reweigh them