Fatty acid is carboxylic acid with long hydrocarbon chains. Fatty acid differs with the length of the hydrocarbon chain. Fatty acids can be divided into
- Saturated fatty acids
- Unsaturated fatty acids
Non-essential fatty acids are fatty acids that can be synthesised by the body. Examples of non-essential fatty acids for humans are oleic acid, stearic acid, cerotic acid and palmitic acid.
Essential fatty acids are fatty acids required by the body but are not synthesised by the body. Among the essential fatty acids needed by both humans and animals include linoleum acid and arachidonic acid.
Essential fatty acids are fatty acids required by the body but are not synthesised by the body. Among the essential fatty acids needed by both humans and animals include linoleum acid and arachidonic acid.
Lipids can be classified into three major groups:
- Triglyceride
- Phospholipids
- Waxes
- Steriod
triglyceride
All fats and oils are triglycerides. A triglycerides molecule is formed through condensation reaction between fatty acids and one glycerol molecule. Each fatty acid molecule is linked to glycerol by an ester bond, -COO. Hydrolysis of a triglyceride molecule produces fatty acid molecules and glycerol molecule.
Physical properties
|
Functions
|
phospholipids
Phospholipid molecule is formed from the condensation of one glycerol molecule and one phosphoric acid molecule.
Glycerol + 2 fatty acids + phosphoric acid -> Phospholipid acids
Physical properties
|
Functions
|
steroids
Steroid has a very different structure compared to lipid but is classified together with lipid because of their similar nature. All steroid molecules have four fused rings of carbon atoms. Different steroids have different functional groups attached to this ensemble of rings.
|
Examples of steroids
Other examples: Vitamin D, bile acid and adrenaline
lipid metabolism
Lipid Transport
Lipid metabolism has to start from the intake of lipids and fats from food.When fat is taken in, it will be digested in the small intestine to form fatty acids and glycerol. The fatty acids and glycerol will then be absorbed into the intestinal mucosa and converted into triacylglycerol (TGA). TGA will then be incorporated with cholesterol and apolipoprotein into chylomicron. Chylomicron is a lipoprotein that aids in transportation of lipid. The chylomicron will then be transported into the lymphatic vessels and blood vessels to the cell tissue. Upon reaching the cell tissue, lipoprotein is then activated by apoliprotein C-II releasing fatty acids and glycerol into the cell. The cell will then store fatty acid and glycerol. |
What's Next?
Fatty acids and glycerol are stored in cell, but fatty acids enter the mitochondria and generates energy. Fatty acids itself cannot enter the mitochondria. Therefore, it has to change it's form into fatty acyl coA by the help of CoASH and ATP. The enzyme catalysing this reaction is acyl-coA synthetase. Fatty acid have to change into acyl coA to be recognised by the mitochondria so that energy is produced. Fatty acid itself cannot produce energy unless it is change into fatty acyl coA.
Fatty acids and glycerol are stored in cell, but fatty acids enter the mitochondria and generates energy. Fatty acids itself cannot enter the mitochondria. Therefore, it has to change it's form into fatty acyl coA by the help of CoASH and ATP. The enzyme catalysing this reaction is acyl-coA synthetase. Fatty acid have to change into acyl coA to be recognised by the mitochondria so that energy is produced. Fatty acid itself cannot produce energy unless it is change into fatty acyl coA.
However, fatty acyl coA can only enter the inter membrane space of the mitochondria. In order for the fatty acyl coA to enter the matrix of mitochondria, a carrier is need, which is carnithine. Carnithine will combine with acyl coA to form acylcarnithine and CoASH. This reaction is catalyse by the enzyme carnithine acyltransferase I. Acylcarnthine will then enter into the matrix of the mitochondria. This process is also reversible. In the mitochondria matrix, the acylcarnithine will then convert back into carnithine with the help of CoASH to produce acyl coA. Acyl coA is the energy producing factor in fatty acids.
How does acyl coA help in yielding energy?
Degradation of acyl coA happens. The process is called β-oxidation. This process occurs in four steps:
After one cycle of β-oxidation process, to will produce:
FADH2, NADH will enter the electron transport chain in the respiration and produces ATP. The acetyl coA produces will enter the Krebs cycle and produces ATP. Whole the acyl coA produced can be recycled and used again. |
Fatty acid biosynthesis
Occurs in cytoplasm. The usual product of fatty acid metabolism is Palmitate. During two-carbon elongation, malonyl-ACP is used. Malonyl-ACP is the main substrate. This process involves ACP was the acyl carrier protein.There are 6 steps in on cycle of synthesis:
|
The differences of fatty acid degradation and fatty acid synthesis