Lipase enzyme in human body

Lipases (triacylglycerol acyl hydrolases) are water-soluble enzyme catalyzing hydrolysis of lipids in food, thereby breaking down fats into glycerol and free fatty acids, so they can be absorbed in the intestines. Lipase is produced in the pancreas, mouth, and stomach.

Lipases, together with amylases and proteases, constitute the three major known digestive enzymes. Its function is to digest fats and lipids, helping to maintain correct gallbladder function.

The three different types of lipases are:
*Pharyngeal lipase, which is produced in the mouth and is most active in the stomach. It is an enzyme secreted by the acinar cells of the sublingual gland that aids lipid digestion. Although found in saliva, it plays only a minimal role in breaking down lipids in the mouth.

*Hepatic lipase, which is produced by the liver and regulates the level of fats (lipids) in the blood. It is a multifunctional protein that modulates lipoprotein metabolism and atherosclerosis. Hepatic lipase functions as a lipase and as a ligand that facilitates lipoprotein uptake by cell surface receptors and proteoglycans.

*Pancreatic lipase, which is produced by the pancreas and released into the beginning of the small intestine (duodenum) to continue the digestion of fats.

Most people produce enough pancreatic lipase, but people with cystic fibrosis, Crohn disease, and celiac disease may not have enough lipase to get the nutrition they need from food.
Lipase enzyme in human body

What are lipids?

Lipids are organic compounds that contain hydrocarbons which are the foundation for the structure and function of living cells.

Lipid molecules contain large hydrocarbon portion and not many polar functional group, which accounts for their solubility behavior. Their intermolecular interactions are dominated by the hydrophobic effect and van der Waals interactions.

Lipids are water insoluble organic compounds. They are hydrophobic (nonpolar) or amphipathic (containing both nonpolar and polar regions)
*Free fatty acids
*Triacylglycerols
*Phospholipids
*Glycolipids
*Steroids

Fatty acids are “carboxylic acids (or organic acid), often with a long aliphatic tails (long chains), either saturated or unsaturated.” When a fatty acid is saturated it is an indication that there are no carbon-carbon double bonds and if the fatty acid is saturated it is an indication that it has at least one carbon-carbon double bond.

Lipids are major components of cell membranes, and are responsible for most of the permeability filter functions of membranes. Membranes act as barriers to separate compartments within eukaryotic cells, and to separate all cells from their surroundings.

A lipid abnormality is one of the causal factors of cardiovascular disease. Excess LDL cholesterol (say a total serum cholesterol > 4-5mmol/L) is the most widely accepted risk factor for heart disease. Excess triglycerides (say >1.8mmol/L) are probably important in CHD but this is controversial. A low concentration of HDL cholesterol (say less than 1.0mmol/L) is also accepted as a major risk factor.
What are lipids?

Functions of lipids and fats

Lipids are a broad group of diverse and naturally occurring, organic compounds. Lipids are studied by nutritionists who investigate how intake of fats in human diet affects the composition of various parts of the body, e.g. heart, the liver and the brain. Lipids play a large role when it comes to energy storage and the structure of cells.

They are divided into four main groups consisting of fats, lipids, hormones and steroids.  The difference between fats and lipids is that fats are a subset of lipids.

In general, fat performs four functions in the body. It provides energy, essential fatty acids, structural components and regulatory functions.

*One of the major roles of fat is to serve as fuel molecules. The immediate sources of energy for the body are the free fatty acids in the circulation liberated from adipose triglycerides by the enzyme lipase.  Triacylglycerol fatty acids provide long-term storage of fuel that can be mobilized during food storage, for growth and during vigorous exercise. They are amore highly concentrated form of metabolic energy than carbohydrates. The main depot is the adipose tissue.

*The body has a remarkable ability to synthesize many compounds and this including excess protein and carbohydrates can be converted to fat.

*Fat in the form of triglycerides, phospholipids, cholesterol and cholesterol esters are important to the structure, composition and permeability of membranes and cell walls. Body fat: can hold organs in place: absorbs shock and: insulates the body against rapid temperature changes or excessive heat loss. Phospholipids are water soluble and may aid in the transport of other fats in and out of cells.

Lipids are present as a bilayer in biological membranes, as a layer on the surface of the skin and in the lung surfactant lipid. Because of their specialized functions, their composition is conservative.

*Regulatory functions. Triglycerides in pure state are relatively tasteless, but they absorb and retain flavors of food.  Fats provide texture that enhances palatability and they delay emptying of the stomach and contribute to feeling of satiety.

Dietary fat serves as a carrier for the fat-soluble vitamins A, D, E and K and as an aid to their absorption in the intestine.
Functions of lipids and fats

Classification of Lipids

Classification of Lipids
Lipids include all substances that are extractable from biological materials with the usual fat solvents (ether, chloroform, benzene, carbon tetrachloride, acetone, etc). Certain lipids are an energy source for the cell, others are structural compounds (particularly important are the lipid constituents of cell and organelle membranes), and still other function as hormones. This diversity of function recalls the not too remote past when lipids were considered to be inert constituents of adipose cells.

Of the many compounds classified as lipids, only fraction is significant in the diet, or in the structure and function of the human cell. The following classification is limited to lipids of importance in animal nutrition and excludes the fat soluble vitamins that, although properly classified as lipids, following the classic practice of nutritionist.

A. Simple Lipids
Fatty acids
Neutral fats (mono-, di- and triacyl glycerols)
Wax
*Sterol ester
*Nonsterol ester

B. Compound Lipids
Phospholipids
*Phosphatidic acids, lecithin, cephalins, etc
*Plasmalogens
*Sphinghomyelins
Glycolipid (carbohydrate containing)
Lipoproteins (lipids in combination with protein)

C. Derived Lipids, alcohol (including sterols and hydrocarbons)
Classification of Lipids