Triglycerides (also known as triacylglycerols or triacylglycerides) are glycerides in which the glycerol is esterified with three fatty acids. They are the main constituent of vegetable oil and animal fats.A major component of lipid is Triglyceride and it is membrane bound.
where R, R’, and R” are fatty acids; the three fatty acids can be all different, all the same, or only two the same.
Chain lengths of the fatty acids in triglycerides can be from 4 to 22 C atoms, but 16 and 18 are most common. Shorter chain lengths are found in butter for instance. Almost without exception, only even numbers of carbon atoms are found in natural fatty acids – due to the way they are bio-synthesised from acetic acid.
A lipoprotein is a biochemical assembly that contains both proteins and lipids and may be structural or catalytic in function. Lipoproteins may be enzymes, proton pumps, ion pumps, or some combination of these functions.
Examples include the high density and low density lipoproteins of the blood and the transmembrane proteins of the mitochondrion and the chloroplast.
The lipids are often an essential part of the complex, even if they seem to have no catalytic activity themselves. To isolate transmembrane lipoproteins from their associated membranes, detergents are often needed.
All cells need fats and, for all animal cells, cholesterol to build the multiple membranes which cells use to both control water, and water soluble elements, and to organize their internal structure and protein enzymatic systems.
Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the homeostatic mechanisms involved are only partly understood. A higher intake in food leads to a net decrease in endogenous production and vice versa.
The main regulatory mechanism is the sensing of intracellular cholesterol in the endoplasmic reticulum by the protein SREBP (Sterol Regulatory Element Binding Protein 1 and 2). In the presence of cholesterol, SREBP is bound to two other proteins: SCAP (SREBP-cleavage activating protein) and Insig-1.
When cholesterol levels fall, Insig-1 dissociates from the SREBP-SCAP complex, allowing the complex to migrate to the Golgi apparatus, where SREBP is cleaved by S1P and S2P (site 1/2 protease), two enzymes that are activated by SCAP when cholesterol levels are low.
Cholesterol is primarily synthesized from acetyl CoA through the HMG-CoA reductase pathway in many cells/tissues. About 20–25% of total daily production (~1 g/day) occurs in the liver, other sites of higher synthesis rates include the intestines, adrenal glands and reproductive organs.
For a person of about 150 pounds (68 kg), typical total body content is about 35 g, typical daily internal production is about 1 g and typical daily dietary intake is 200 to 300 mg. Of the 1,200 to 1,300 mg input to the intestines (via bile production and food intake), about 50% is typically reabsorbed into the bloodstream.
Cholesterol is a steroid lipid, found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. Most cholesterol is not dietary in origin, it is synthesized internally.
It is present in higher concentrations in tissues which either produce more or have more densely packed membranes; for example the liver, spinal cord, brain and atheroma.
Cholesterol plays a central role in many biochemical processes, but is best known for the association of cardiovascular disease with various lipoprotein cholesterol transport patterns in the blood.
The name originates from the Greek chole- (bile) and stereos (solid), as researchers first identified cholesterol in solid form in gallstones.
Heart disease is caused by narrowing of the coronary arteries that feed the heart. Like any muscle, the heart needs a constant supply of oxygen and nutrients, which are carried to it by the blood in the coronary arteries.
Many people assume that high cholesterol is a problem that affects middle-aged adults only. In fact, many people don’t even worry about their cholesterol when they are younger, eating all the fatty convenience foods they want, assuming that their early diet makes no difference.
Nothing could be further from the truth. More children today suffer from high cholesterol. In fact, the numbers of children who are taking cholesterol drugs is on the rise! Some studies have suggested that a childhood of poor eating choices can contribute to higher cholesterol later in life.
Besides this, many of the eating habits learned in childhood affects eating in adulthood. Children who are used to eating high-fat foods and convenience foods are more likely to make the same choices as adults. Switching to healthy foods in adulthood may be harder for children who have made less-than-heart-healthy food choices all their lives. For all these reasons, controlling food intake and lifestyle choices even in early life can contribute to life-long heart health and good cholesterol levels.