LIPIDS

INTRODUCTION

Lipids are organic substances relatively insoluble in water and soluble in organic solvent like Alcohol and Ether. A lipid is a macrobiomolecule that is soluble in nonpolar solvents. Non-polar solvents are typically hydrocarbons used to dissolve other naturally occurring hydrocarbon lipid molecules that do not (or do not easily) dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, and phospholipids.

Function of Lipids

1. Provide energy.

2. Useful for fat soluble vitamin.

3. Regulate body temperature.

4. Forms the protective layer of vital organs.

5. Lipids are needed to make hormones.

Dietary source of Lipids

Meat, eggs, cheese, fried fast food, cookies, butter, curd, diary products with cream, ghee.

Classification of Lipids

They are classified into 3 types:

-Simple lipid

These are esters of fatty acid with alcohols and known as simple lipid. They are mainly of 2 types-

*Fat and Oil - These are esters of fatty acid with glycerol. e.g., Triglycerol.

*Wax - These are esters of fatty acids with higher molecular weight. e.g., Bees wax.

-Complex lipid

These are esters of fatty acid with alcohol containing additional groups such as Phosphate, Nitrogenous base, Carbohydrate and Protein. They are further divided as follows

(a) Phospholipids - They contain phosphoric acid and frequently a nitrogenous base. This is in addition to alcohol and fatty acids.

(b) Glycolipids - These lipids contain a fatty acid, carbohydrate and nitrogenous base. Glycerol and phosphate are absent.

(c) Lipoproteins - Macromolecular complexes lipids with proteins.

-Derived lipid

These are obtained by hydrolysis of simple and compound lipids. e.g. Cholestrol, Testosterone.lipids. These include glycerol and other alcohols, fatty acids, mono- and diacylglycerols, lipid (fat) soluble vitamins, steroid hormones, hydro-carbons and ketone bodies.

Digestion of Fats

Fats are digested by lipases that hydrolyze the glycerol fatty acid bonds.Lipases are found in the mouth, the stomach, and the pancreas. Because the lingual lipase is inactivated by stomach acid, it is formally believed to be mainly present for oral hygiene and for its anti-bacterial effect in the mouth.

In stomach, less digestion of fat with the help of mild gastric lipase. Then in duodenum, fat convert into emulsified fat due bile salt. 

-Emulsified fat convert into diglyceride fat and fatty acid in the presence of  Pancreatic lipase enzyme.

-Diglyceride fat convert into monoglyceride fat and fatty acid in the presence of lipase enzyme. And, monoglyceride convert into glycerol and fatty acids.

Absorption of Fats

-Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solution.

-Micelles are attached at the microvilli surface of upper part of small intestine.

-All the digested product passively diffuse into mucosal cells.

-Short and medium chain fatty acids due to require bile slat for their absorption.

-They absorb directly into intestinal cell and they enter portal blood rather than lymph and transport to the liver, bound to serum albumin.

Lipid metabolism

Lypolysis: Breakdown of fats and other lipids by hydrolysis to release into fatty acid.

Esterification: Reaction between alcohol and carboxylic acid to make esters.

Beta-oxidation: It is a metabolic process involving multiple steps by which fatty acid molecules are broken down to produce energy.

Ketogenesis: Ketogenesis is process in which production of ketone bodies through breakdown of fatty acids and ketogenic amino acid.

Lipid profile test

A complete cholesterol test is also known as lipid panel or lipid profile. It is use for the measure of the amount of cholesterol level in body. This includes:

-Serum cholestrol test

-HDL test

-LDL test

-VLDL test

-Triglycerides test

A complete cholesterol test — also called a lipid panel or lipid profile — is a blood test that can measure the amount of cholesterol and triglycerides in your blood. A cholesterol test can help determine your risk of the buildup of plaques in your arteries that can lead to narrowed or blocked arteries throughout your body (atherosclerosis). A cholesterol test is an important tool. High cholesterol levels often are a significant risk factor for coronary artery disease.

A complete cholesterol test includes the calculation of four types of fats (lipids) in your blood:

• Total cholesterol. This is a sum of your blood's cholesterol content.
• High-density lipoprotein (HDL) cholesterol. This is called the "good" cholesterol because it helps carry away LDL cholesterol, thus keeping arteries open and your blood flowing more freely.
• Low-density lipoprotein (LDL) cholesterol. This is called the "bad" cholesterol. Too much of it in your blood causes the buildup of fatty deposits (plaques) in your arteries (atherosclerosis), which reduces blood flow. These plaques sometimes rupture and can lead to a heart attack or stroke.
• Triglycerides. Triglycerides are a type of fat in the blood. When you eat, your body converts calories it doesn't need into triglycerides, which are stored in fat cells. High triglyceride levels are associated with several factors, including being overweight, eating too many sweets or drinking too much alcohol, smoking, being sedentary, or having diabetes with elevated blood sugar levels.

In next topic I'm going to discuss "Disorders related to Protein". For any correction and suggestion please comment. I will try to perform better.

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