(C)(ii) practical investigation into factors affecting membrane structure and permeability

What do u use to cut the beetroot into equal slices

Cork-borer

What do you do after you cut the beetroot

Rinse to remove excesss anthocyanin (*a pigment in the vacuole of beetroot cell*)

What do you actually do with the beetroot cells?

Add each one to a test tube with 5cm3 of water at different temperatures using water bath

What do use to measure how much light is absorbed?

Colorimeter - use colour that is complementary

What should the results show and why

As temperature increase the absorption increases and less gets transited because more pigment is diffused out of cells

This is because membrane permeability increases and phospholipids move more (not as highly packed)

The higher temperature causes the proteins to denature and further breakdowns the membrane

What are 2 limitations to the beetroot temperature practical? How would you overcome

Some parts might have more pigment than others

So make sure to conduct several repeats using diff parts of beetroot

Beetroot pieces may offer in size

So use cork screw

Why do you set up colour standards for testing the effect of ethanol on beetroot membrane

The test is a semi- quantitative test and the colour standards are where you have beetroot juice (100% beetroot and dilute it with water to make 89% 60% 40% and so on.

This is to have something to compare it to at the end

What s the process

Set up different concentration of ethanol and place in water bath

Blot the discs on paper towel to remove excess juice from cutting

Then place in tube with ethanol for 5 minutes

Shake every minute

Then compare with colour standards

Why should you shake the test tube every 1 minute

Discs with ethanol may stick together and reduce rate of diffusion

Pigment may build around the discs which would reduce the concentration gradient and slow down diffusen

What should you see for the results

100% ethanol would have increased rate of difffuin and more pigment leaks

How would you improve the test

Use a colorimeter to make it less subjective