Required Practical 4

Question 1

you were provided with beetroot discs that were washed thoroughly before the start of the investigation.

explain why it was important to wash the beetroot discs?

Answer 1

to make sure all pigment washed off

Question 2

describe a suitable control for this investigation

Answer 2

• distilled water
• 2 beetroot discs

Question 3

explain why a control would be necessary

Answer 3

to show alcohol was causing leakage of pigment

Question 4

explain why you were instructed to shake the test tubes every minute

Answer 4

• maintain diffusion gradient for pigment
• prevent discs sticking together
• increase contact of all surfaces with alcohol

Question 5

explain why you were instructed to pour the alcohol IMMEDIATELY from the experimental test tube in to the clean test tube

Answer 5

make sure all discs were in contact with alcohol for same length of time

Question 6

you were given discs taken from fresh beetroot in your investigation

explain why your results would have been different if you had used cooked beetroot

Answer 6

• heating destroys plasma membrane
• denatures proteins
• lot of pigment released during cooking

Question 7

you used a water bath in your investigation

explain why a decrease in temperature of 5 degrees would affect the results

Answer 7

• reduces kinetic energy
• lower rate of diffusion
• molecules move slower
• membrane less fluid

Question 8

2 students carried out the same investigation as you did

they worked in the same practical session and followed the same procedure

they worked accurately but found their results were different

suggest one reason for this

Answer 8

• variation in beetroot
• variation in judging colour

Question 9

the student started drawing his curve from the origin,

was he correct to do this

Answer 9

No

• curve drawn on graph should not extend beyond data collected

Question 10

phospholipids dissolve in alcohol

explain the shape of the increase in the curve between alcohol concentrations of 40 and 80 percent

Answer 10

• phospholipids are IN MEMBRANES
• membrane breaks down faster at higher conc of alcohol
• more pigment moves out of cells

Question 11

after further investigation a student found out that a point was not an anomaly

suggest why the curve levels out

Answer 11

• conc of pigment inside and outside of tissue reached equilibrium
• maximum membrane damage