Investigate the Effect of Temperature on Cell Membranes and Membrane Structure

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Investigate the Effect of Temperature on Cell Membranes and Membrane Structure


If you read a recipe for cooked beetroot it will usually recommend
that you don’t remove the outer skin of the beetroot and don’t cut off
al the stalk and root if you want to avoid getting lots of red dye in
the cooking water. Beetroot contains red pigments called betalains,
located within the cell vacuole. Normally the pigments can’t pass
through membranes but they leak out when the beetroot is cooked.

Aim – The aim of this practical is to use beetroot to examine the
effect of the temperature on cell membranes and relate the effects
observed to membrane structure. To function correctly a cell needs to
be able to control transport across the
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The polar heads lie at both surfaces, the kind of three-dimensional
enclosed structure shown above can form. The real shape tends to be
globular (minimizing surface to volume ratio), and there are so many
more bipolar molecule pairs than shown here that the radius of
curvature lacks the kind of strain and distortion shown at the corners
of this drawing.

A membrane is a phospholipid bilayer studded with proteins,
polysaccharides and other sorts of lipids. This patchwork of molecules
is like a mosaic. Because the molecules move about within their
respective layer, the membrane behaves like a fluid. This is why the
model is called the Fluid-mosaic model.

There have been many theories as to the nature of the cell membrane.
In 1935 Daniellie and Davson put forward a possible structure, which
was widely accepted. Their model was composed of a double lipid layer
coated on each side by protein. They Estimated that the membrane was
so thick, with the introduction of the electron microscope, membranes
could be clearly seen for the first time. Plasma membranes of both
animal and plant cells showed a characteristic three-layered
(trilarninar) appearance.

As we apply heat on to the beetroot, this denatures the proteins
creating "holes" in the membrane allowing pigment to be leeched out.
The denaturing of the proteins incorporated with the added kinetic
energy added to the polysaccharides allows pigment to be…