How will changing the percentage of glucose concentration affect the light transmission percentage from the release of betacyanin caused by the permeability of cell membranes of beetroot cells?

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Claudia Cheng

IA 3: Unit 2 SL/HL Investigating transport across membranes

Version 2- The effect of a factor of cell membrane function

Design and perform an experiment to determine the effect of a factor on the cell membranes.

Introduction

The cell membrane is the boundary that separates the internal parts of the cell from surroundings. Substances that move in or out of the cells must pass across the cell membrane.

Beetroot (Beta vulgaris) cells contain red pigment called betacyanin. The red pigment is contained in a large vacuole inside the cells. The vacuole is separated from the cytoplasm of the cell by its own membrane. The membrane of the vacuole in a living cell does not normally let the red pigment through it. If the membranes of the cell are damaged, however, the red pigment may leak out of the vacuole and out of the cell. The extent of the damage to the membrane can be measured by the amount of red pigment escaping the cell.

Research Question

How will changing the percentage of glucose concentration affect the light transmission percentage from the release of betacyanin caused by the permeability of cell membranes of beetroot cells?

Hypothesis

I predict that as the concentration of glucose increases, the solution will become darker in colour thus the light transmission percentage will decrease. This is due to the water potential of the surrounding glucose solution being lower than the water potential inside the beetroot cell causing water to exit the cell through osmosis. As the cell becomes flaccid for a long period of time, it will start to wilt. This causes the cell membrane to tear away from the cell wall and the permeability to increase so the red pigment betacyanin would be realeased.

Independent variable

Dependent variable

Controlled Variables

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Equipment

Half a beetroot

Scapel

Glucose solution

Distilled water

Colorimeter

Test tubes

Stopwatch

Core borer

Water bath

White tile

Clamp

10 cm3 Measuring cylinder

Diagram

Experimental Method

Prepare 5 test tubes and label them: 20%, 40%, 60%, 80%, 100%.

To prepare these different glucose concentration solutions, use 2 different 10cm3 measuring cylinder, one for water, and one for the glucose to ensure accuracy.

The table below shows the amount of glucose and distilled water need to prepare different glucose concentrations.

Obtain long pieces of beetroot from a ...

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