These are naturally occurring organic compounds that are insoluble in water.
Lipids functions as:
- Energy Storage
- Making Biological Membranes
- Insulation eg. Animal fat (blubber)
- Protection – e.g. protecting plant leaves from drying up
- Acting as hormones
They are made from two molecules: Glycerol and Fatty Acids. They may be saturated or unsaturated.
A fatty acid is saturated if every possible bond is made with a Hydrogen atom, such that there exist no C=C bonds. Saturated fatty acids on the other hand do contain C=C bonds.
If fatty acids are unsaturated, it does contain C=C bonds and so because of this their shape is altered from a saturated molecule so the molecules in the Lipid push apart, thus making it more fluid and oily.
Types of lipids
Basically one glycerol molecule bonded with three fatty acid molecules as seen below . Triglycerides are hydrophobic and so insoluble in water.
Phospholipids are similar to triglycerides in they consist of a glycerol ‘back bone’ and fatty acid ‘tails’
This means the phosphate group will orientate itself towards water and away from the rest of the molecule, and also gives rise to the special properties that allow phospholipids to be used to form membranes
Prostaglandins Thromboxanes & Leukotrienes
Natural hormones have an extraordinary range of biological effects. They can lower gastric secretions, stimulate uterine contractions, lower blood pressure, influence blood clotting and induce asthma-like allergic responses.
Steroids may be recognized by their tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring, as shown in the diagram to the right. The four rings are designated A, B, C & D as noted, and the peculiar numbering of the ring carbon atoms (shown in red) is the result of an earlier misassignment of the structure. The substituents designated by R are often alkyl groups, but may also have functionality. The R group at the A:B ring fusion is most commonly methyl or hydrogen, that at the C:D fusion is usually methyl. The substituent at C-17 varies considerably, and is usually larger than methyl if it is not a functional group. The most common locations of functional groups are C-3, C-4, C-7, C-11, C-12 & C-17. Ring A is sometimes aromatic.
Cholesterol is a waxy steroid which is produced by the liver. Cholesterol is vital for normal body function. Every cell in our body has cholesterol in its outer layer.