Figure 5. A phospholipid is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone. The phosphate may be modified by the addition of charged or polar chemical groups.
Several chemical R groups may modify the phosphate. Choline, serine, and ethanolamine are shown here. These attach to the phosphate group at the position labeled R via their hydroxyl groups.
In the presence of water, some phospholipids will spontaneously arrange themselves into a micelle Figure 6. The lipids will be arranged such that their polar groups will be on the outside of the micelle, and the nonpolar tails will be on the inside.
Under other conditions, a lipid bilayer can also form. This structure, only a few nanometers thick, is composed of two opposing layers of phospholipids such that all the hydrophobic tails align face-to-face in the center of the bilayer and are surrounded by the hydrophilic head groups.
A phospholipid bilayer forms as the basic structure of most cell membranes and are responsible for the dynamic nature of the plasma membrane. Figure 6. In the presence of water, some phospholipids will spontaneously arrange themselves into a micelle.
Source: Created by Erin Easlon own work. As mentioned above, if you were to take some pure phospholipids and drop them into water that some of the phospholipid would spontaneously form into micelles. This sounds like a process that could be described by an Energy Story. Go back to the Energy Story rubric and try to create an Energy Story for this process — I expect that the steps involving the description of energy might be difficult at this point we'll come back to that later but you should be able to do at least the first three steps.
You can also constructively critique each other's work to create an optimized story. The phospholipid membrane is discussed in detail in a later module. It will be important to remember the chemical properties associated with the functional groups in the phospholipid in order to understand the function of the cell membrane. Lipids Lipids are a diverse group of hydrophobic compounds that include molecules like fats, oils, waxes, phospholipids, and steroids. Fats and oils A common fat molecule or triglyceride.
Facciotti own work Note: possible discussion The models of the triglycerides shown above depict the relative positions of the atoms in the molecule. Note: possible discussion Natural fats like butter, canola oil, etc. The physical properties of these different fats vary depending on two factors: The number of carbons in the hydrocarbon chains; The number of desaturations, or double bonds, in the hydrocarbon chains.
Figure 3. Sterols Steroids are lipids with a fused ring structure. Submit Cancel. Comments Please Post Your Comment. No comments yet. Save Note Note. Save Cancel Delete. Next Prev Close Edit Delete. You have authorized LearnCasting of your reading list in Scitable. Do you want to LearnCast this session? This article has been posted to your Facebook page via Scitable LearnCast.
Change LearnCast Settings. Scitable Chat. Register Sign In. Long fatty acid chains arrange themselves into a spherical globule called a micelle form which are achieved by the hydrophobic chains associating together while their hydrophilic heads face outwards, interacting with the water; such structures can act as various detergents or soaps [5]. Triacylglycerols are referred to as 'natural fats' and their molecules tend to cluster together to form droplets and keep away from water [6].
The fact that they isolate themselves as hydrophobic droplets makes storage easy, for example, storage of energy in cells which can be released when required via enzyme action.
Triacylglycerols also can act as thermal and mechanical insulators and in aquatic animals, can supply buoyancy [7]. Phospholipids are a group of compounds that are similar to triacylglycerols except that one of the fatty acid chains is instead replaced by a phosphate group ; several other varying small molecules may be attached to the phosphate giving a group of different structures [8].
The phospholipids position themselves in a bilayer; the hydrophobic groups in contact with each other on the inside of the bilayer and the hydrophilic groups on the outsides of the bilayer. The role of phospholipid bilayer is to allow the conditions inside the cell to be different to those outside and to control the movement of substances into and out of the cell.
It is the phospholipids in the membrane that control the movement of the substances into and out of the cell. As only lipid-soluble molecules to pass through them therefore entering and leaving the cell and water-soluble molecules cannot pass through therefore are prevented from entering and leaving the cell [9].
0コメント