cholestrol

What type of molecule is cholesterol?

Cholesterol is a lipid and a steroid.

Which form of cholesterol affects membrane fluidity and permeability?

Only free cholesterol (not esterified cholesterol) affects membrane fluidity and permeability.

What are the major physiological roles of cholesterol?

• Regulates membrane fluidity
• Aids intracellular transport
• Involved in cell signaling and nerve conduction
• Precursor for bile acids, steroid hormones, and vitamin D (calcitriol)

Where is exogenous cholesterol absorbed in the digestive system?

In the lower jejunum and ileum, in the presence of bile acids and salts.

What happens to cholesterol inside enterocytes?

Most of it is esterified and incorporated into chylomicrons, which enter the lymph and then the blood.

What are the endogenous sources of cholesterol?

• Synthesized from acetyl-CoA (from glucose, fatty acids, amino acids)
• Occurs in the liver, intestines, adrenal glands, and reproductive organs

Which dietary components stimulate cholesterol synthesis?

Saturated fatty acids and trans fats increase cholesterol synthesis.

How is cholesterol transported in the blood?

• Chylomicrons → exogenous cholesterol
• VLDL, LDL, HDL → endogenous cholesterol
• LDL is the major cholesterol carrier

How is cholesterol eliminated from the body?

Excreted by the liver into bile and the digestive tract
~50% is reabsorbed by the small intestine

What can a high concentration of cholesterol in the gallbladder lead to?

Formation of gallstones

What is hypercholesterolemia and its cutoff value?

Hypercholesterolemia is high blood cholesterol, defined as >200 mg/dL.

What are primary causes of hypercholesterolemia?

Genetic factors

What are secondary causes of hypercholesterolemia?

• Poor diet
• Lack of exercise
• Diseases like diabetes mellitus and hypothyroidism

What lifestyle changes are recommended to treat hypercholesterolemia?

• Low-glucose, low-fat diet
• Avoid cholesterol sources
• No alcohol or smoking
• Regular exercise

What medication is used to treat hypercholesterolemia and how does it work?

Statins, which inhibit HMG-CoA reductase, the key enzyme in cholesterol synthesis.

What are the possible consequences of hypocholesterolemia?

• Depression
• Cancer
• Cerebral hemorrhage

What is the treatment for hypocholesterolemia?

• Diet high in good cholesterol
• Omega-3 supplements