lipids r

What are the three main classes of lipids?

Simple lipids, compound lipids, and derived lipids.

What are simple lipids composed of?

Esters of fatty acids with alcohols.

What distinguishes compound lipids from simple lipids?

Compound lipids contain additional groups like phosphate or carbohydrate.

What are derived lipids?

Products of hydrolysis of simple or compound lipids or substances associated with lipids in nature.

Name four types of derived lipids.

Fatty acids, alcohols, steroids, and fat-soluble vitamins (A, D, E, K).

What are phospholipids composed of?

Fatty acids, alcohol, and a phosphate group.

What are glycolipids composed of?

Sphingosine alcohol, fatty acid, and a carbohydrate radical.

Name three types of glycolipids.

Cerebrosides, sulpholipids (sulphatides), and gangliosides.

Where are glycolipids mainly found?

Brain tissues, myelin sheath, and RBC membranes.

What is the function of glycolipids in cell membranes?

They act as receptors and provide recognition properties.

What is the basic structure of a steroid nucleus?

Four fused rings with 17 carbon atoms.

What are the three main groups of steroids?

Sterols, bile acids, and steroid hormones.

What is the most important sterol in animals?

Cholesterol.

Name three steroid hormones.

Testosterone, cortisol, aldosterone.

What are the classifications of steroid hormones?

Sex hormones (e.g., estrogen, progesterone) and corticoids (glucocorticoids and mineralocorticoids).

What are the sources of cholesterol?

Exogenous (dietary) and endogenous (synthesized by cells).

What is the normal plasma level of cholesterol?

120–200 mg/dL.

What percentage of plasma cholesterol is esterified?

70% as cholesteryl esters.

What is the recommended cholesterol level to reduce heart disease risk?

Less than 200 mg/dL.

In which tissues is cholesterol concentration highest?

Nervous tissue, liver, adrenals, gonads, skin, and adipose tissue.

How does cholesterol affect membrane fluidity at warm temperatures?

It decreases fluidity by limiting fatty acid tail movement.

How does cholesterol affect membrane fluidity at low temperatures?

It increases fluidity by preventing close packing of phospholipids.

What vitamin is derived from cholesterol?

Vitamin D (from 7-dehydrocholesterol).

What is the role of cholesterol in bile acid formation?

It is a precursor for bile salts.

How is cholesterol excreted from the body?

Mainly in bile as bile salts, and in stool as cholesterol, cholesteryl esters, and dehydrocholesterol.

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