Cholesterol is responsible for the stability of all cell membranes. Cholesterol is also produced by the cells of the human body. The most active part of cholesterol in the body is usually the cholesterol ester bond. It is not present in fat and is not available after a meal. The most common form of the structure cholesterol in food is naturally occurring cholesterol compounds, that are made through enzymatic reactions. These cholesterol compounds appear to be stable throughout most of the physiological functions of a cell. Cholesterol is present in several different substances in the body, including proteins, fats, carbohydrates, and minerals. Cholesterol is also found in the body in the form of the esters, esterified cholesterol, and cholesterol ester molecules.
Cholesterol, the most abundant lipid in the human body, is found mainly in animal fat. Approximately 20% of total body fat is formed of fat from animal sources; 40% comprises fat from human sources. The amount of fat from animals that contributes to total body fat has been estimated to be 35% of total fat. A great proportion of the fat in a human being arises from animals, and of the human fat found in food, more than 90% comes from animal sources.
The body of a mammal varies throughout the lifespan; the amount of fat in a human infant is about 20% greater than an adult's body fat. This increases during childhood. The majority of the fat in humans comes from animal sources. Over time the body burns the energy stored in fat as a major source of heat in the human body. In animals, the main source of energy derived from fat consists of the use of the stored energy in body fat as an energy substrate. Most mammals have very simple organs for storing energy.
The liver and muscles contain the largest stores of fat. The liver metabolizes a substantial portion of fat; it provides the energy that the muscles consume for most of their activities. In humans the liver and muscles can store only about 9% of total body fat. Although fats and carbs are stored in the liver, all fat is converted to alcohol in the liver. The primary source of alcohol in the human body is alcohol dehydrogenase, or alcohol dehydrogenase. Alcohol is produced in the liver and can be metabolized into acetaldehyde and acetate in the liver. It is this alcohol that causes the sensation of intoxication called intoxication. Alcohol also increases the production and activity of fatty acids in the liver.
Fats and carbs are stored in the muscles, in the skin, and in the joints, bones, joints, and nerves. However, the fat that makes up the body can only be stored in the fat cells, which are usually found near the skin. Fat cells are much smaller than fat cells found in the liver. The largest cells of the nervous system are found in the cerebral cortex, the center of brain functions.
An important role of cholesterol is to help form cell membranes. It also plays a vital role in the formation and functioning of fatty acids in the cells. The triglyceride-containing lipids are found primarily in the cells lining the blood vessels. The other lipids are found in the cytoplasm (cell-like tissue). However, they are synthesized mainly in the adipocytes.
The fat tissue consists primarily of three types (fatty acids, chylomicrons and phospholipids): chylomicrons, which are found predominantly in visceral fat; phospholipids, which are found in the adipose tissue and the liver; and triglycerides, which are found in the fatty tissue and fat cells.
Cholesterol has about 250 carbon atoms. Each carbon atom carries a pair of electrons which make electrons of the right type (a positive charge) and vice versa. The electrons are transferred to molecules so that they can be used for chemical reactions. Cholesterol molecules carry a very narrow range of charged atoms (1 - 32 electrons) which can be either positively or negatively charged. The exact properties of the electrons are determined by the number, shapes, orientation, shape of the atoms, and degree of charge concentration.
The different types of lipids and their respective functions and mechanisms are reviewed here. For an overview of the metabolism of cholesterol, please see the "Fatty Acids, Chylomicrons, Lipoproteins (Chylomicron, Tissue-Specific Lipids) and Monosaccharides" chapter of our online textbook "Cholesterol in Health and Disease".
Chylomicrons are found in visceral fat, especially in visceral subcutaneous and subcutaneous fat cells of the abdominal muscle. The term refers to a mixture of triglycerides (a complex carbohydrate) and lipoproteins (a lipid that carries oxygen for transportation molecules from the liver).
The triglyceride-containing lipids are composed of 4 main types, fatty acids: (A), (B), (C), (D), and unsaturated fatty acids: (E) fatty acids are found mostly in the chylomicron (B) and phospholipids: (F) fatty acids are found mostly in the peripheral fat and fat cells (and also in tissues) (1). Chylomicrons, chylomicrons are found predominantly in visceral fat tissues
Fatty acids are composed of a lipid chain called an alpha (-Δ)-oleate that carries one or more oxygen molecules for the transport of ATP molecules. It can also carry one or more carbon atoms as a carbon moiety including the carbon atom that makes up the carbon chain. The oxygen molecule is the source of energy, whereas that of some other fatty acids can be used for energy transfer.