WHY

Is It Important to Become Familiar with Cholesterol?

"Cholesterol is a vital constituent of cell membranes and the precursor for steroid hormones and bile acids. It is clearly essential to life, yet its deposition in arteries is associated with cardiovascular disease and stroke, two leading causes of death in humans. In a healthy organism, an intricate balance is maintained between the biosynthesis, utilization, and transport of cholesterol, keeping its harmful deposition to a minimum."

D. Voet, J.G. Voet and C.W. Pratt: "Fundamentals of Biochemistry", 3rd ed.

1. Cholesterol is a crucial component of cell membranes

 

 

• Cholesterol is the third major lipid in membranes.
• Cholesterol is compact, rigid, hydrophobic molecule with a polar hydroxyl group.
• The hydroxyl group of cholesterol is oriented towards the aqueous phase (polar heads of phospholipids) and gives hydrophilic character to this end of cholesterol molecule.
• The cholesterol to polar lipid ratios affect stability, fluidity, permeability, and protein mobility. Cholesterol also controls the microstructure of membranes.
• Cholesterol is especially abundant in myelinated structures of the brain and central nervous system and almost absent from the inner mitochondrial membrane.

 

 

 

2. Cholesterol is the precursor of bile salts

 

 

• Cholesterol is abundant in bile.
• The solubilization of hydrophobic molecules of cholesterol is aided by bile phospholipids and bile salts. They prevent cholesterol from precipitating in gallbladder in form of gallstones.
• Bile salts are metabolites of cholesterol.
• Cholesterol protects gallbladder membranes from irritating and harmful effects of bile acids and bile salts.

 

 

 

 

3. Cholesterol is the precursor of steroid hormones

 

Cholesterol is the precursor of ALL steroid hormones including progesterone, estrogen, testosterone, corticosteroids, and aldosterone. 

Thus, cholesterol is crucial for human reproduction, response to the environment, and preservation of human species.

 

  

4. Cholesterol is the precursor of vitamin D

 

 

• The various forms of vitamin D, which are really hormones, are sterol derivatives.

• Active vitamin D increases Ca²⁺ concentration in serum by promoting the intestinal absorption of dietary Ca²⁺. This increases the deposition of Ca²⁺ in bones and teeth.

 

  

 

  

 

 

 

 

Value: 1 Cholesterol is a hydrophilic molecule. True False	Value: 1 Cholesterol is a flexible molecule. True False
Value: 1 How many hydroxyl groups are present in one molecule of cholesterol?	Value: 1 How many methyl groups are present in the steroid nucleus of cholesterol?
Value: 1 The hydrocarbon tail of cholesterol has hydro_______ character. Spell out the whole word.	Value: 1 The organ whose structures (membranes) are very rich in cholesterol.

 

Value: 1 Cholesterol is a precursor for the following: a. Bile salts b. Vitamin D c. Testosterone d. Arachidonic acid e. Progesterone [mark all correct answers]

Value: 1 Cholesterol is involved in the following processes: a. Formation of plasma membrane b. Gall stone formation c. Formation of the mitochondrial membrane d. Absorption of calcium into the bones e. Protection against stroke [mark all correct answers]

 

5. Excessive levels of cholesterol in blood lead to cardiovascular disease 

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