CHOLESTEROL TEST Flashcards
___________is an unsaturated steroid alcohol containing four rings (A, B, C, and D) called___________________, and it has a single C-H side chain tail similar to a fatty acid in its physical properties.
Cholesterol
perhydrocyclopentanophenanthrene
The only hydrophilic part of cholesterol is the______ group in the A-ring.
hydroxyl
Cholesterol is, therefore, also an______ lipid and is found on the surface of lipid layers along with phospholipids.
amphipathic
_________is oriented in lipid layers so that the four rings and the side chain tail are buried in the membrane in a parallel orientation to the fatty acid acyl chains on adjacent phospholipid molecules.
Cholesterol
The___________ on the cholesterol A-ring faces outward, away from the lipid layer, allowing it to interact with water by noncovalent hydrogen bonding.
polar hydroxyl group
Cholesterol can also exist in an esterified form called_______, with the hydroxyl group conjugated by an ester bond to a fatty acid, in the same way as in triglycerides.
cholesteryl ester
In contrast to free cholesterol, there are no polar groups on________, making them very hydrophobic.
cholesteryl esters
Because it is not charged, cholesteryl esters are classified as a________ lipid and are not found on the surface of lipid layers but instead are located in the center of lipid drops and lipoproteins, along with triglycerides.
neutral
Cholesterol is almost exclusively synthesized by animals, but plants do contain other sterols similar in structure to cholesterol.
Cholesterol is also unique in that, unlike other lipids, it is not readily catabolized by most cells and, therefore, does not serve as a source of_______.
fuel
Cholesterol can, however, be converted in the liver to primary bile acids, such as (2), which promote fat absorption in the intestine by acting as detergents.
cholic acid and chenodeoxycholic acid
A small amount of cholesterol can also be converted by some tissue, such as the adrenal gland, testis, and ovary, to steroid hormones, such as (3)
glucocorticoids
mineralocorticoids
estrogens
a small amount of cholesterol, after first being converted to 7-dehydrocholesterol, can also be transformed to _______ in the skin by irradiation from sunlight.
vitamin D3
The CDC reference method for cholesterol is based on a chemical method devised by_____
Abellet al.
1
The enzyme_______ cleaves the fatty acid residue from cholesteryl esters, which comprise about two thirds of circulating cholesterol, converting them to______
cholesteryl ester hydrolase
unesterified or free cholesterol
2
The free cholesterol is reacted by the second enzyme,_______, producing hydrogen peroxide, a substrate for a common enzymatic: color reaction using________ to couple two colorless chemicals into a colored cornpound.
The intensity of the resulting color, proportional to the amount of cholesterol, can be measured by a spectrophotometer, usually at a wavelength around_____.
cholesterol oxidase
horseradish peroxidase
500 nm
