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To Investigate How the Permeability of the Membrane Changes With Temperature.

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To Investigate How the Permeability of the Membrane Changes With Temperature Introduction All living cells are surrounded by a membrane, which controls the transport of substances moving into and out of a cell. "Membranes are vital to separate the cell form the outside world" 1 They also separate compartments inside the cell to protect important processes and events within the organelles in the cell. Regulation of transport across the membranes of organelles, especially in eukaryotic cells, is vital. 2 Diagram of a prokaryotic cell with only membranes labelled Diagram of palnt cell, only membanes Sm,ae with animal cell From these diagrams, it can be seen that membranes are present abundantly in all living cells, and must play an important part in the metabolism of the cell. For example, the plasma membrane allows the movement of several substances into and out of the cell. ...read more.


Because the tails are non-polar, it is difficult for polar molecules or ions to pass through this part of the membrane. Therefore, the bilayer acts as a barrier against water-soluble substances. Cholesterol molecules also have hydrophilic heads and hydrophobic tails. They have several functions in the cell membrane:- 1. They help control the fluidity of the membrane, preventing it from becoming too fluid, or too rigid 2. They are important in the mechanical stability of membranes, preventing them from breaking up too easily. 3. The hydrophobic regions prevent ions or polar molecules from passing through - this is particularly important in the mycelium sheath around nerve cells, where leakage of ions would slow down nerve impulses. Proteins also have a variety of functions in the membrane:- 1. Transmembrane channel proteins, or transport proteins, span the whole cell membrane. ...read more.


Hydrogen bonds form between strongly polar groups. They can be broken by high temperatures or pH changes. b) Disulphide bonds form between cysteine molecules. They can be broken by reducing agents. c) Ionic bonds form between ionized amine and carboxylic acid groups. They can be broken by pH changes. d) Hydrophobic interactions occur between polar and non-polar chains. As the structure of proteins is specific to its function, it is imperative that the bonds are not broken. Thus the surrounding conditions, such as the temperature and pH, must remain constant; "proteins are generally adapted to work at set temperatures...high temperatures, as well as other stressful conditions effectively denatures proteins or generally renders them 'unserviceable'. Such damaged molecules are of no use to the cell and may even be harmful." 1 www.cytochemistry.net/Cell-biology/membrane_Intro.htm 2 Cambridge advanced sciences Biology 1 1 unknown book title 1 http://www.jdaross.mcmail.com/cell2.htm 1 Biological Science 1 2 Cambridge advanced sciences Biology 1 ...read more.

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