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.

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Hammad Naveed

Why Does The Colour Leak Out Of Cooked Beetroot?

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 partially permeable cell membrane.

Theory – To understand how the red pigment leaks out of the beetroot it is essential that we understand the molecular Structure of a plasma membrane.

A membrane is a phospholipid bilayer. This means that it has two layers of molecules called phospholipids. Each of these phospholipid molecules
has two parts:

• A 'head' that will mix with water but not with fat (i.e. it is hydrophilic)

• Two 'tails' that will mix with fat but not with water (i.e. they are
hydrophobic).

In the phospholipid bilayer, the hydrophilic heads are always on the outside
of the membrane. The hydrophobic tails are always on the inside of the
membrane. Alone, this arrangement of phospholipids would form
a barrier to water and to water-soluble substances. However, other
molecules are scattered among the phospholipids. These include lipids
(including cholesterol in the membranes of animals), proteins and
polysaccharides. The proteins in membranes are of special interest to us. This is because
they have a number of important functions. Proteins function as:

• Carriers for water-soluble molecules (such as glucose)

• Channels for ions (such as sodium and chloride ions)

• Pumps, which use energy to move water-soluble molecules and ions

• Receptors, which enable hormones and nerve transmitters to bind to
specific cells

• Recognition sites, which identify a cell as being of a particular type

• Enzymes, which speed up chemical reactions at the edge of the
membrane

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The ways that substances move across cell membrane are

  1. Diffusion 
  2. Active transport 
  3. Facilitated diffusion 
  4. Osmosis 

The one we are focusing on is diffusion. The rate of which diffusion occurs while temperature is being changed. 

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 ...

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This is a well structured and written report. 1. There is information that has been included that needs to be rewritten 2. The analysis section needs to quote data to back up the claims that are made 3. The evaluation needs to suggest further opportunities ****