REQUIRED PRACTICALS

Question 1

outline the method to investigate cell membrane permeability

Answer 1

1. place 5 equally cut beetroot pieces into separate test tubes
2. place each test tube in a water bath at different temperatures for 20 minutes
3. remove beetroot piece from each tube, leaving only the colored liquid
4. using the blue filter on a colorimeter, add distilled water to a cuvette and calibrate it
5. using pipettes, transfer liquid from first test tube into a clean cuvette and add to colorimeter
6. read/record absorbable of solution
7. repeat readings for the remaining test tubes

Question 2

what do higher levels of absorbance show in the membrane permeability experiment?

Answer 2

• more pigment released
• higher the permeability of the membrane

Question 3

what filter is used on the colorimeter during the membrane permeability experiment?

Answer 3

• blue filter

Question 4

explain the results of the membrane permeability experiment show?

Answer 4

• as temperature increases, membrane permeability increases (shown by higher absorbance readings)
• phospholipids have more energy at high temps, so move more
• phospholipid bilayer may begin to melt
• volume of water inside cells expands, putting pressure on membrane
• causes transport proteins to deform
• transport proteins become denatured, so can’t control substances entering or leaving the cell

Question 5

state 3 limitations of the membrane permeability experiment

Answer 5

1. some cuvettes may be thicker or scratched, so absorb slightly more light
2. beetroot pieces may not be identical in size
3. some parts of the beetroot may contain more pigment than others

Question 6

how to ensure the unidentifiable sizes of beetroot doesn’t effect the membrane permeability experiment results

Answer 6

• cut as accurately as possible, using a scalpel and a ruler
• repeat multiple times and calculate a mean average

Question 7

state the independent variable in the membrane permeability experiment

Answer 7

temperature

Question 8

state the dependent variable in the membrane permeability experiment

Answer 8

percentage absorbance

Question 9

state 5 control variables of the membrane permeability experiment

Answer 9

• same SA:V ratio of beetroot pieces
• length of time in the water bath
• volume of water on the surface of the beetroots after rinsing
• volume of water in each boiling tube
• same type + age of beetroot

Question 10

how to ensure each beetroot has the same SA:V ratio in the membrane permeability experiment

Answer 10

use a ruler to ensure all pieces are the same length

Question 11

how to ensure each beetroot spends the same length of time in their water bath during the membrane permeability experiment

Answer 11

use a stopwatch to time 20 minutes

Question 12

how to ensure each beetroot has the same volume of water on it after rinsing initially, during the membrane permeability experiment

Answer 12

roll over a paper towel 3 times

Question 13

how to ensure each boiling tube has the same volume of water in it during the membrane permeability experiment

Answer 13

use a 5cm3 syringe to measure 5cm3 of water for each tube

Question 14

how to ensure each beetroot piece has the same age/type, during the membrane permeability experiment

Answer 14

all cylinders should be from the same beetroot/same type of beetroot