Biochemical Foundations of Human Vital Activity - Volkov, N. I., & Nesen, E. N. 2000

Biochemical Foundations of Human Vital Activity
Lipid Biochemistry
Chemical Composition and Biological Role of Lipids

The Human Body stores a vast amount of energy in the form of fat. While Liver and Skeletal Muscle Glycogen can provide about 2,000 kcal of energy, fats in Muscles and adipose tissue provide approximately 70,000 kcal. Fat reserves in the body are virtually inexhaustible, as running a marathon consumes less than 1 kg of them. Fats serve as the primary energy substrate during aerobic endurance exercise. Their utilization during muscular activity helps maintain high physical performance and delays the onset of fatigue.

Lipids, or fats (from the Greek lipos meaning fat), are a Class of Organic compounds insoluble in Water. They dissolve in organic Solvents such as ether, chloroform, or benzene. Lipids also include Fat-soluble Vitamins, Prostaglandins, pigments, and other water-insoluble compounds that can be extracted from Tissues using organic solvents.

Fat molecules, like carbohydrate molecules, consist of carbon, hydrogen, and oxygen atoms. However, the oxygen content relative to other atoms is significantly lower than in CARBOHYDRATES, as seen, for example, in the formula for fat (tristearin): С₅₇Н₁₁₀О₆. Consequently, The oxidation of fats requires a substantially greater amount of oxygen than the oxidation of carbohydrates.

Fats perform A wide variety of biological Functions in the body, the primary ones being:

✵ Energy storage. The breakdown of 1 g of fat releases 39 kJ (9.3 kcal) of energy, which is significantly more than from the oxidation of carbohydrates. The body can store enough energy in the form of glycogen to sustain basal METABOLISM for no more than a day, whereas triglycerides can provide energy for several months.

✵ Structural. Lipids, in complex with Proteins, serve as Structural components of all Cell membranes. Consequently, they participate in transmembrane transport, receptor signaling, and other membrane processes.

✵ Regulatory or hormonal. The regulatory function is carried out by Steroid Hormones, as well as tissue hormones called prostaglandins, which are synthesized from polyunsaturated Higher Fatty acids.

✵ Thermoregulatory. Fats located in the subcutaneous adipose tissue protect the body from hypothermia because they are poor conductors of heat.

✵ Protective. Lipid layers protect Internal Organs from mechanical trauma, while also shielding nerve endings and Blood Vessels from compression and bruises. Fat imparts elasticity to the Skin, and saturated fatty acids provide bactericidal properties.

✵ Solvent function. Many organic compounds dissolve in fats, including vitamins A, D, E, and K, enabling them to easily cross vascular walls and cell membranes, and to be transported within biological fluids.