Cholesterol is a lipophilic molecule that is essential for human life. It has many roles that contribute to normally functioning cells. For example, cholesterol is an important component of the cell membrane. It contributes to the structural makeup of the membrane as well as modulates its fluidity. Cholesterol functions as a precursor molecule in the synthesis of vitamin D, steroid hormones (e.g., cortisol and aldosterone and adrenal androgens), and sex hormones (e.g., testosterone, estrogens, and progesterone). Cholesterol is also a constituent of bile salt used in digestion to facilitate absorption of fat-soluble vitamins A, D, E, and K.
Since cholesterol is mostly lipophilic, it is transported through the blood, along with triglycerides, inside lipoprotein particles (HDL, IDL, LDL, VLDL, and chylomicrons). These lipoproteins can be detected in the clinical setting to estimate the amount of cholesterol in the blood. Chylomicrons are not present in non-fasting plasma.
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