Fatty Acids: A blessing to living body

Lipids are macromolecules comprises about 15-2-% of human body weight. Triglycerides are considered as the most important lipids share 85-90% of lipid mass. Triglycerides are stored in human adipose tissue and provide energy to the body. Triglycerides are known as highly concentrated energy stores. This energy can be anhydrous and reduced. We yield a 9kcal g-1 of energy from the complete oxidation of the fatty acids. This energy is much higher than the energy produced from oxidation of carbohydrates and proteins. The large difference in energy is due to the fact that fatty acids are much reduced than other biological compounds. Other major reason is that, fatty acids are non-polar and are present in anhydrous form. On the other hand, proteins and carbohydrates are polar compounds and found in hydrous form. We say that, 1g of glucose molecules binds with the 2g of water. Simultaneously, one gram of anhydrous fat is used to store energy that is six times higher than one gram of hydrated glycogen. Due to this universal fact, we consider triglyceride not glycogen as the major energy survival in evolution.

In Mammals:

In mammals, cytoplasm of adipose tissues acts as major site of accumulation of triglycerides. Triglycerides form large globule by coalescence of small droplets. These globules may occupy the large volume of the cell. Adipose tissues are highly specialized tissues for the production and storage of triglycerides and used for the locomotion process.

In Birds:

The feasibility of triglycerides as energy storage products can be illustrated by the capability of migratory birds, which can across a long seasonal distance without eating any food. We can take the example of American golden plover and the other one is ruby throated sparrow. The golden plover covers the distance from Alaska to the southern tip of North America. They flew over the sea in the form of groups, where they cannot eat any food. The humming bird can continuously covers the distance across the Gulf of Mexico. Only fatty acids are used for such prodigious activities.

Fatty Acid oxidation:

Fatty acids present in the body oxidized into small compounds through a process called “Beta Oxidation”. It is define as

“Oxidation of fatty acids on Beta Carbon”

This results in the production of two carbon fragment compounds, on a sequential note.

Types of Beta Oxidation: There are two types of “Beta Oxidation” depends upon the number of carbon present in the chain.

• Odd chain beta oxidation of fatty acids

• Even chain beta oxidation of fatty acids

Stages of Beta oxidation: There are three main stages of beta oxidation. These are;

• In the cytoplasm, activation of the fatty acid

• Entrance of fatty acids into mitochondrial membrane

• Complete oxidation of fat in the mitochondrial matrix

Explanation:

Activation process: First step involves the activation of fatty acids to acyl CoA by the action of acyl CoA synthetases. It is an energy gaining process. During this process two high energy phosphate groups are utilized.

Transportation of Acyl CoA into mitochondria: Mitochondrial matrix is selective towards the fatty acids. To for the acids to gain entrance in the matrix, they go through a process called “Carnitine shuttle”. The acyl molecule is transported across the membrane by a specific Carnitine protein. Carnitine acyl transferase II catalyzed this reaction. After entering into the membrane, Carnitine separates and returns back to its origins.

Beta oxidation: During each cycle of beta oxidation, a two carbon compound is produced, called Acetyl CoA. This process goes through series of reaction and produces Acetyl CoA that enters into the Citric acid cycle and produces a large amount of energy for body need.

Overall Reaction: Overall reaction for each turn of beta oxidation is as follow;

Palmitoyl-CoA + CoA + FAD + NAD+ + H2O Myristoyl-CoA + acetyl-CoA + FADH2 + NADH + H+