Cholesterol is the principal sterol in all vertebrate cells (McGraw-Hill 2002); trace amounts also are found in plant membranes.
The 1987 report of National Cholesterol Education Program, Adult Treatment Panels suggest the total blood cholesterol level should be less than 200 mg/dl for normal blood cholesterol.
Cholesterol is insoluble in blood, but is transported in the circulatory system bound to one of the varieties of lipoprotein, spherical particles that have an exterior composed mainly of water-soluble proteins.
The hydroxyl group on cholesterol interacts with the phosphate head of the membrane, while the bulky steroid and the hydrocarbon chain is embedded in the membrane.
Cholesterol can exist free or as an esther in which a fatty acid is bound to the hydroxyl group by an ester bond (McGraw-Hill 2002).
Recently, cholesterol has also been implicated in cell signaling processes, where it has been suggested that it forms lipid rafts in the plasma membrane.
Konrad Bloch and Feodor Lynen shared the Nobel Prize in Physiology or Medicine in 1964 for their discoveries concerning the mechanism and regulation of the cholesterol and fatty acid metabolism.
Major dietary sources of cholesterol include eggs, beef, and poultry (USDA 2005).
Cholesterol is more abundant in those animal tissues that can either synthesize more or have more abundant, densely-packed membranes; for example, the liver, spinal cord, brain, and atheromata (arterial plaques).
flax seed, peanut), also contain cholesterol-like compounds, phytosterols, which are suggested to help lower serum cholesterol (Ostlune et al.
Conversely, the total cholesterol can be within normal limits, yet be made up primarily of small LDL and small HDL particles, under which conditions atheroma growth rates would still be high.
Some research indicates that cholesterol may act as an antioxidant (Smith 1991).
Some cholesterol derivatives, (among other simple cholesteric lipids) are known to generate the liquid crystalline cholesteric phase.
The apolipoproteins forming the surface of the given lipoprotein particle determine from what cells cholesterol will be removed and to where it will be supplied.
Instead, it is transported in the bloodstream by lipoproteins—protein "molecular-suitcases" that are water-soluble and carry cholesterol and triglycerides internally.
Cholesterol is required to build and maintain cell membranes; it regulates membrane fluidity over a wider range of temperatures.
The basis of this is that Total cholesterol is defined as the sum of HDL, LDL, and VLDL.
The main regulatory mechanism for cholesterol biosyntheis is the sensing of intracellular cholesterol in the endoplasmic reticulum by the protein SREBP (Sterol Regulatory Element Binding Protein 1 and 2).
Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the homeostatic mechanisms involved are only partly understood.
Cholesterol is required in the membrane of mammalian cells for normal cellular function.
High-density lipoprotein (HDL) particles transport cholesterol back to the liver for excretion, but vary considerably in their effectiveness for doing this.
Longe (2005) concludes that the most beneficial means to control cholesterol levels in probably a healthy diet and regular exercise.
Low glycemic foods promote a slow but steady rise in blood sugar levels following a meal, which increases the level of HDL, and lower total cholesterol and triglycerides.
The deleterious impact of cholesterol can largely be ameliorated by personal responsibility—specifically, diet and exercise, such as regular exercise and reducing or eliminating foods high in fat or practicing a low glycemic diet.
The level of cholesterol can influence development of atherosclerotic plaque.
Between 200 and 239 mg/dl is considered borderline-high, and over 240 mg/dl is considered high cholesterol.
Cholesterol is primarily synthesized from acetyl CoA through the HMG-CoA reductase pathway in many cells and tissues.
Cholesterol can come directly from the diet or via biosynthesis in the body.
Cholesterol is minimally soluble in water; it cannot dissolve and travel in the water-based bloodstream.
Cholesterol is excreted from the liver in bile and reabsorbed from the intestines.
The former scavenges circulating LDL from the bloodstream, whereas HMG-CoA reductase leads to an increase of endogenous production of cholesterol (Anderson 2003).
There appear to be seasonal variations in cholesterol levels in humans, more, on average, in winter (Ockene et al.
Having large numbers of large HDL particles correlates with better health outcomes, and hence it is commonly called "good cholesterol."
Cholesterol is important in the production and metabolism of other vital substances.
A ratio of total cholesterol to HDL—another useful measure—of far less than 5:1 is thought to be healthier.
Abolitionists from Dartmouth College founded the experimental, interracial Noyes Academy in Canaan, New Hampshire in 1835.
Cholesterol is either synthesized in the endoplasmic reticulum of these cells, or derived from the diet, in which case it is delivered by the bloodstream in low-density lipoproteins.
Cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including the caveolae-dependent endocytosis and clathrin-dependent endocytosis.
The role of cholesterol in caveolae-dependent and clathrin-dependent endocytosis can be investigated by using methyl beta cyclodextrin (M?CD) to remove cholesterol from the plasma membrane.
The name cholesterol originates from the Greek chole- (bile) and stereos (solid), and the chemical suffix -ol for an alcohol, as researchers first identified cholesterol in solid form in gallstones in 1784.
Plants have trace amounts of cholesterol, so even a vegan diet, which includes no animal foods, has traces of cholesterol.
The level of cholesterol can influence development of atherosclerotic plaque.
Dietary intake of cholesterol itself is not the key factor influencing levels of cholesterol in the blood, due to regulatory mechanisms, but rather consumption of saturated dietary fats.
The average amount of blood cholesterol varies with age, typically rising gradually until one is about 60-years-old.
Food not containing animal fats generally contains no cholesterol or negligible amounts.
Steroids and their metabolites often function as signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of cell membranes. Steroids such as cholesterol decrease membrane fluidity. Similar to lipids, steroids are highly concentrated energy stores.