Plasma membrane: Difference between revisions
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A plasma membrane | A plasma membrane encapsulates each and every [[Cell|cell]]. The plasma membrane is necessary to allow different concentrations of substances to be maintained between the cell and it's environment. [[Eukaryotic cells|Eukaryotic cells]] have internal membranes which surround [[Organelles|organelles]], allowing different constituent concentrations within the cell. | ||
The structure of the plasma membrane is made up of a [[Lipid bilayer|lipid bilayer]] embedded with [[Proteins|proteins]] and [[Cholesterol|cholesterol]]. Most lipid bilayers are comprised of [[Phospholipid|phospholipids]], the most common being [[Phosphatidylcholine|phosphatidylcholine]]. The head part of it is made up of a [[Phosphate|phosphate]] and a [[Hydrophilic|hydrophilic]] [[Choline|choline]], the tail component of the phospholipid is comprised of two fatty acid chains, long hydrocarbon structures with a chemically active COOH. Since the head is hydrophilic and the tails are [[Hydrophobic|hydrophobic]], the phospholipid is said to be [[Amphipathic|amphipathic]]. The structure of the bilayer is such that the tails are shielded from contact with [[Water|water]], creating a selectively-permeable barrier. <br> | The structure of the plasma membrane is made up of a [[Lipid bilayer|lipid bilayer]] embedded with [[Proteins|proteins]] and [[Cholesterol|cholesterol]]. Most lipid bilayers are comprised of [[Phospholipid|phospholipids]], the most common being [[Phosphatidylcholine|phosphatidylcholine]]. The head part of it is made up of a [[Phosphate|phosphate]] and a [[Hydrophilic|hydrophilic]] [[Choline|choline]], the tail component of the phospholipid is comprised of two fatty acid chains, long hydrocarbon structures with a chemically active COOH. Since the head is hydrophilic and the tails are [[Hydrophobic|hydrophobic]], the phospholipid is said to be [[Amphipathic|amphipathic]]. The structure of the bilayer is such that the tails are shielded from contact with [[Water|water]], creating a selectively-permeable barrier. <br> | ||
Revision as of 19:05, 9 January 2011
A plasma membrane encapsulates each and every cell. The plasma membrane is necessary to allow different concentrations of substances to be maintained between the cell and it's environment. Eukaryotic cells have internal membranes which surround organelles, allowing different constituent concentrations within the cell.
The structure of the plasma membrane is made up of a lipid bilayer embedded with proteins and cholesterol. Most lipid bilayers are comprised of phospholipids, the most common being phosphatidylcholine. The head part of it is made up of a phosphate and a hydrophilic choline, the tail component of the phospholipid is comprised of two fatty acid chains, long hydrocarbon structures with a chemically active COOH. Since the head is hydrophilic and the tails are hydrophobic, the phospholipid is said to be amphipathic. The structure of the bilayer is such that the tails are shielded from contact with water, creating a selectively-permeable barrier.
The plasma membrane has many functions and is a fundamental part to the cell. It communicates with the environment and other cells by means of a glycocalyx, a system of protein-linked and lipid-linked carbohydrates. It allows passage of selective molecules in and out of the cell via carrier or channel proteins embedded within the membrane, and it regulates cell growth, shape change, movement and division.
The membrane is associated with proteins, both integral and peripheral which act as either: transporters, linkers, receptors or enzymes.
The lipids within the bilayer can freely move, they can diffuse laterally along the membrane, or rotate along their axis. They are said to be fluid within the system.This fluidity is dependent on:
- the length of the phospholipid tail
- whether the tail is saturated or not
- the presence of cholesterol.