The Effect of Temperature on the Permeability of Cell Membranes

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  • Topic: Cell membrane, Phospholipid, Cholesterol
  • Pages : 7 (1889 words )
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  • Published : October 27, 2008
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The effect of temperature on the permeability of cell membranes

Introduction
For my coursework, I intend to assess how temperature affects the plasma membrane of a cell. For this I will use the cell of a beetroot. Background
What is a cell membrane?
The cell membrane, also called the plasma membrane is a semipermeable lipid bilayer which is the surface of all cells that surrounds the cytoplasm. The membrane is called a bilayer as it has a double layer of phospholipids. Within the cell membrane there are many biological molecules, proteins and lipids, which are involved in cellular processes, and also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall. It is selectively permeable and chooses what molecules enter and leaves the cell and also maintains the cells potential.

This following picture is a diagram of the fluid mosaic with all the different molecules labeled:

Phospholipids –

Phospholipids are a type of lipids which are key parts of all biological molecules, along with glycolipids, carbohydrates and proteins.

The circular head of the phospholipid is the phosphate component. This is hydrophilic (Water Liking) therefore faces the aqueous part that surrounds the membrane.

The tail of the phospholipid is the fatty acid component. This is the opposite of the phosphate as it is hydrophobic (Dislikes Water) therefore the tails point inwards towards each other as it is a bilayer forming a non-polar interior.

Cholesterol-

Cholesterols are the lipids found in the membranes of all tissues. The name cholesterol comes from the Greek words chole (Bile) and stereos (solid).

The phospholipid molecule is like the cholesterol molecule in the way that the cholesterol also has hydrophilic (Water Liking) heads and hydrophobic (Dislikes Water) tails, therefore they are able to fit between the phospholipid molecules.

The cholesterol molecule helps keeps the fluidity of the cell membrane balanced so it’s not too fluid like or solid. It is also very important to the membrane as its keep it stable and without the cholesterol the membrane would break and the cell will burst open.

Protiens-

The cell membrane plays host to the protein as it is one of the more popular parts of a membrane that is responsible for its many different activities.

Protiens are very important in a membrane as they have many tasks, most of the proteins act as transport proteins. These are used for bigger molecules like polar molecues and ions. There are a different variety of proteins each one for a different type of ion or molecule and they each control what enters and leave the cell.

An important type of protein within the cell membrane is the globular protein. Unlike the proteins that only play a structural task, globular proteins work as enzymes, messengers, transporters and supply of amino acids.

Some proteins molecules move around with the phospholipid layers whereas some proteins are fixed inside the cell and don’t move and some proteins are also fixed in the outer layer there are also some in the inner layer and proteins around with the whole membrane.

Other proteins could also act as enzymes. Protiens are also important in the roles in the membrane s of organelles. E.g. Membranes of mitochondria and chloroplast, as they are involved in the process of respiration and photosynthesis.

Glycolipids-

Many molecules including glycolipids on the surface of the membrane have carbohydrate chains connected to them. This combination is known as glycolipids or if a protein is attached then glycoprotein.

Environmental Conditions on a Cell Membrane-

The phospholipid bilayer is affected when the temperature of the environment it is in is increased on the membrane.

When the temperature of the membrane is increased the protein starts to denature when the temperature is increased to about 35/45 °c and more. Once the proteins have started to...
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