cho·les·te·rol

Cholesterol (from the Ancient Greek chole- (胆汁) and stereos (solid), followed by the chemical suffix -ol for an alcohol) is an organic molecule. It is a sterol (or modified steroid [改性类固醇]), a type of lipid [类脂]. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell membranes.

Cholesterol is essential for all animal life, with each cell capable of synthesizing it by way of a complex 37-step process. Cholesterol composes about 30% of all animal cell membranes. Plants make cholesterol in very small amounts.

Cholesterol is recycled in the body. The liver excretes cholesterol into biliary fluids [胆道积液], which are then stored in the gallbladder [胆囊], which then excretes them in a non-esterified [非酯化] form (via bile) into the digestive tract [消化道]. Typically, about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream.

Major dietary sources of cholesterol include red meat, egg yolks and whole eggs, liver, kidney, giblets [禽类内脏], fish oil, and butter. Human breast milk also contains significant quantities of cholesterol. Most foods that are rich in cholesterol are also high in saturated fat and thereby may increase the risk of cardiovascular [relating to the heart and blood vessels] disease.

According to the lipid hypothesis [脂质假说], elevated levels of cholesterol in the blood lead to atherosclerosis [动脉粥样硬化] which may increase the risk of heart attack, stroke, and peripheral artery disease.

A human male weighing 68 kg (150 lb) normally synthesizes about 1 gram (1,000 mg) of cholesterol per day, and his body contains about 35 g, mostly contained within the cell membranes.

Eggs do provide a significant amount of your daily recommendation of cholesterol. One large egg contains approximately 186 mg of cholesterol, more than half of the recommended daily intake. However, evidence suggests that eggs have an extremely minor effect on your blood cholesterol levels.

More current testing methods determine LDL ("bad") and HDL ("good") cholesterol separately, allowing cholesterol analysis to be more nuanced. The desirable LDL level is considered to be less than 130 mg/dL (2.6 mmol/L), although a newer upper limit of 70 mg/dL (1.8 mmol/L) can be considered in higher-risk individuals based on some of the above-mentioned trials. A ratio of total cholesterol to HDL—another useful measure - of far less than 5:1 is thought to be healthier.

LDL stands for low density lipoprotein [脂蛋白] and HDL stands for high density lipoprotein. "dL" stands for decilitre, one tenth of a litre, 分升。

六级/考研单词: cholesterol, organism, molecule, modify, indispensable, component, synthesis, compose, weigh, norm, intake, recycle, liver, fluid, tract, breast, saturate, thereby, accord, hypothesis, elevate, stroke, artery, desire, heal, liter