2.8 Investigating why the colour leaks out of beetroots soaked in alcohol Planning
to investigate the effects of different concentrations of alcohol on the membrane structure of a beetroot
Decide what you think will be the effect of alcohol on beetroot cell surface membranes and how this will affect their permeability. Write down your idea as a hypothesis that you can test, and support your idea with biological knowledge. Hypothesis
“The greater the concentration of the alcohol the more red pigments (betalains) move into the solution.” Biological knowledge:
The exposure of the beetroot cell membrane to alcohol makes it more permeable. If there would be no membrane there would be unrestricted movement of the alcohol and water molecules until equilibrium is achieved. The membrane prevents the movement of some molecules. However, higher concentrations of alcohol may denature some proteins as they have a tertiary structure. High concentrations of alcohol will break the hydrogen bonds in the structure of the proteins, this is what makes the cell membrane more permeable as there are now gaps in the cell membrane allowing bigger molecules such as the betalains to get through. The lipids and proteins in the cell membrane would be destroyed allowing the betalains to leak through the cell. Diffusion
Diffusion which is the movement of substances from a higher concentration to a lower concentration through a partially permeable wall will still has to happen as the cell gets its other molecules needed such as carbon dioxide and oxygen through this process. As the cells are now surrounded by alcohol, this will be diffused through the cell membrane as well which destroys the permeability of the cell membrane.
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