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Beetroot Membrane Free essay! Download now

Home > A Level > Biology > Beetroot Membrane

Beetroot Membrane

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Downloads to date: N/A | Words: 1062 | Submitted: 07-Aug-2011
Spelling accuracy: 55.6% | Number of pages: 3 | Filetype: Word .doc


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Beetroot Membrane essay previewBeetroot Membrane essay previewBeetroot Membrane essay preview

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Explains the membrane of beetroot

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BEETROOT PIGMENTS
and membranes –

These pigments are betalain pigments (not, as often thought, anthocyanins), which they replace in some organisms.


They are named after the Beet family of plants (Beta) but are also found in fungi (Fly Agaric - the red, spotted one!).
In petals they presumably attract pollinating insects and may be present in seeds/fruits to encourage birds to eat them and so disperse the seeds.

Man has selected for colour in beetroot, both because it is more attractive but also because it may well be linked to genes for flavour too.
There is no indication that they have any protective function (e.g. against UV light or insect/fungal/viral attack).
Unlike anthocyanins, they are not pH indicators – their colour is stable over a wide range of pH. They are oxidised over time (going brown) and this may be prevented by 0.1% ascorbic acid ( = Vit.C); they are sometimes used as food colourants.

They are found in the vacuole and thus are used as markers for scientists who wish to extract intact vacuoles from plants for research.
To extract the pigment, the membranes must be disrupted. This can be done by heat shock, by detergents or by solvents (e.g. ethanol or acidified methanol). Thin slices have a larger surface area and so leak more pigment; freezing the beetroot first bursts the cell membranes and kills the cells, thus allowing the pigment to be extracted much more quickly.


Effect of Heat:

When you heat a beetroot, you disrupt the cell membranes. A biological membrane is made of a so-called phospholipid bilayer. These are formed because the phospholipids that make it up have a polar "water-loving" (hydrophyllic) head and a “water-hating” (hydrophobic) tail. The tails pack together, exposing only the polar heads to the water. The most effective way of doing this is to create two blankets one atop the other, with the fatty acid tails towards each other. This is the phospholipid bilayer.
In a cell they form sacks. One goes all around the cell (the plasma membrane), others may form vacuoles (such as the tonoplast). Yet others may be like stacks of half empty bags (the endothelial reticulum, which is also continuous with the nuclear envelope. In these lipid seas, there will be a number of proteins in various degrees of submersion. Some span all the bilayer, thus being exposed on both sides. Others just drift on either of its surfaces. Typically, you will find that about 70% of a cell membrane is protein. The water around and within the compartments formed by the phospholipid bilayers is also crammed with protein (= cytoplasm).



So what happens when you heat this? When you heat something you give it energy. Molecules start ...

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