HANDOUT 2- WRITING COMPLETE LAB REPORTS
EXERCISE 1
Given below are the details of an experiment to determine the effect of chemical
substances on membrane permeability. Write the lab report of this experiment.
Experiment No : B1
Theory :

Beetroot contains two sap pigments known as  cyanine and  xanthine which give
different colours when immersed in acidic and alkaline media. Table 01 gives the
colours of these pigments in different media.

Pigments
- a useful indicator of membrane permeability
-typically contained within the vacuole of intact beetroot cells.

Increase in membrane permeability - cause the pigment to leak out of the cell- change
the colour of the media.
 cyanine
 xanthine
Acidic medium
pink
colourless
Alkaline medium
colourless
yellow
Table 01
Method:
1. Cut the provided beetroot cylinder into thin discs.
2. Wash them thoroughly using tap water to remove the pigments on the surface of
the discs.
3. Place the discs in a beaker of water.
4. Pour about 10ml portions of distilled water, HCl, and KOH into separate test tubes.
5. Place the beetroot discs in each of the test tubes containing above three solutions.
6. Leave the discs in the solution for one hour.
7. Record the colour change
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Observations:
solution
Colour after 1hr
Distilled water
no change
HCl
pink
KOH
yellow
Discussion:
1. Explain the results you obtained

Plasma membrane* + tono plast ** (cell) -

Some chemical substances (e.g. HCl, KOH ) – destroy –permeability –
Semi permeable membranes
membrane
 cell sap comes out

Beetroot – contain - distinctive betalains in the cell sap

Betalains from red beetroot - natural pigments- mainly include either yelloworange betaxanthins or red-violet betacyanins (Fu et at., 2020).

Pigments -give different colours - acidic and alkaline media
2. Explain the Precautions taken

Wash discs (thoroughly) – to remove pigments released while cutting –If notcannot observe the correct colour.
References:
Topic of the Article : Red Beetroot Betalains
Sub Topic: Perspectives on Extraction, Processing, and Potential Health Benefits.
Authors: Y. Fu, J. Shi, S. Xie, R.E. Aluko,
Year of publishing: 2020
Name of the Journal: Journal of Agriculture and Food Chemistry
Volume and Issue; Vol. 68(4)
Pages referred: 11595-11611
*
biological membrane that separates the protoplasm from the external environment.
** membrane surrounding a vacuole (a membrane-bound cell organelle) in a plant cell.
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