COMPLEX LIPIDS, DERIVED LIPIDS & LIPOPROTEINS

What are complex lipids?

Lipids containing fatty acids, alcohols, and additional components such as phosphate, nitrogen, or carbohydrates.

What are the main types of complex lipids?

Phospholipids and glycolipids.

What are phospholipids?

Complex lipids containing fatty acids, glycerol or sphingosine, a phosphate group, and an alcohol component.

What are glycolipids?

Complex lipids containing fatty acids, sphingosine, and carbohydrates, but no phosphate.

What is the primary role of complex lipids?

To form the structural framework of cell membranes.

What gives phospholipids their amphipathic nature?

They contain both hydrophobic fatty acid tails and hydrophilic phosphate heads.

What are the two main classes of phospholipids?

Glycerophospholipids and sphingophospholipids.

What are glycerophospholipids?

Phospholipids with a glycerol backbone bonded to two fatty acids and a phosphate group linked to an alcohol.

What are the components of glycerophospholipids?

Glycerol, two fatty acids, phosphate, and an alcohol.

Give examples of alcohol components in glycerophospholipids.

Choline, ethanolamine, serine, glycerol, and inositol.

What is lecithin?

A common glycerophospholipid also called phosphatidylcholine.

What is cephalin?

A glycerophospholipid containing ethanolamine or serine as the alcohol.

What are plasmalogens?

Glycerophospholipids with one fatty acid replaced by an unsaturated ether group.

Where are plasmalogens found?

In the heart and brain tissues.

What are sphingophospholipids?

Phospholipids that contain sphingosine instead of glycerol as the backbone.

What is sphingosine?

An 18-carbon amino alcohol with a long hydrocarbon chain and one double bond.

What is ceramide?

A compound formed when a fatty acid bonds to the amino group of sphingosine.

What are sphingomyelins?

Sphingophospholipids that contain phosphate and choline attached to ceramide.

Where are sphingomyelins found?

In the myelin sheath surrounding nerve cells.

What is the function of sphingomyelins?

To insulate nerve fibers and facilitate rapid nerve impulse transmission.

What are glycolipids also known as?

Glycosphingolipids.

What are glycolipids composed of?

Fatty acids, sphingosine, and one or more sugar units.

What are the main types of glycolipids?

Cerebrosides and gangliosides.

What are cerebrosides?

Glycolipids containing a single sugar residue such as glucose or galactose.

Where are cerebrosides found?

In the brain and myelin sheath of nerves.

What are gangliosides?

Glycolipids containing complex oligosaccharides and sialic acid.

Where are gangliosides found?

In gray matter of the brain and nerve endings.

What is the role of glycolipids?

Cell recognition, communication, and protection.

What are derived lipids?

Substances derived from simple and complex lipids by hydrolysis that still retain lipid characteristics.

What are the main classes of derived lipids?

Steroids, eicosanoids, and fat-soluble vitamins.

What are steroids?

Lipids with a characteristic four-ring fused carbon structure called the steroid nucleus.

What are examples of steroids?

Cholesterol, steroid hormones, and bile acids.

What is the function of steroids?

Serve as structural components and signaling molecules.

What is cholesterol?

The most abundant steroid in the human body and an essential component of cell membranes.

What are the roles of cholesterol?

Membrane stability, precursor to steroid hormones, bile acids, and vitamin D.

Where is cholesterol synthesized?

Mainly in the liver.

What is the structure of cholesterol?

Contains a hydroxyl group, a double bond, and a branched hydrocarbon tail.

Is cholesterol amphipathic?

Yes, because of its polar hydroxyl group and nonpolar ring structure.

What is the normal plasma concentration of cholesterol?

About 150–200 mg/dL.

What are bile acids?

Oxidized derivatives of cholesterol that help emulsify fats in digestion.

Where are bile acids produced?

In the liver.

Where are bile acids stored?

In the gallbladder.

What is the role of bile acids in digestion?

To emulsify lipids, aiding in their breakdown and absorption.

What are steroid hormones?

Hormones derived from cholesterol that regulate metabolism, reproduction, and salt balance.

What are the main classes of steroid hormones?

Sex hormones and adrenocorticoid hormones.

What are sex hormones?

Steroid hormones involved in reproduction and development.

Give examples of male sex hormones.

Testosterone and androsterone.

Give examples of female sex hormones.

Estrogen and progesterone.

What are adrenocorticoid hormones?

Steroids produced by the adrenal cortex that regulate metabolism and salt-water balance.

Give examples of adrenocorticoid hormones.

Cortisol, corticosterone, and aldosterone.

What are eicosanoids?

Derived lipids formed from arachidonic acid that act as local signaling molecules.

What are the three main types of eicosanoids?

Prostaglandins, thromboxanes, and leukotrienes.

What are prostaglandins?

Eicosanoids that regulate inflammation, pain, and fever.

What are thromboxanes?

Eicosanoids that promote platelet aggregation and blood clotting.

What are leukotrienes?

Eicosanoids involved in allergic and inflammatory responses.

How long is the effect of eicosanoids?

Short-lived and act locally near their site of synthesis.

What enzyme converts arachidonic acid into prostaglandins?

Cyclooxygenase (COX).

What drugs inhibit prostaglandin synthesis?

Aspirin and other NSAIDs.

What are lipoproteins?

Complexes of lipids and proteins that transport lipids through the bloodstream.

Why are lipoproteins needed?

Because lipids are insoluble in water and need transport carriers.

What are the components of lipoproteins?

Lipid core (TAGs and cholesterol esters) and outer shell (phospholipids, cholesterol, and proteins).

What are apoproteins?

The protein components of lipoproteins that determine their function and destination.

How are lipoproteins classified?

By their density: chylomicrons, VLDL, LDL, and HDL.

What are chylomicrons?

Lipoproteins that transport dietary TAGs from the intestine to tissues.

What is VLDL?

Very low-density lipoprotein that carries TAGs from the liver to tissues.

What is LDL?

Low-density lipoprotein that carries cholesterol to tissues

known as “bad cholesterol.”

Why is LDL considered bad cholesterol?

Because excess LDL can deposit cholesterol in arterial walls, causing atherosclerosis.

What is HDL?

High-density lipoprotein that carries cholesterol from tissues back to the liver

known as “good cholesterol.”

Why is HDL considered good cholesterol?

It removes excess cholesterol and prevents plaque formation.

What is the desirable total blood cholesterol level?

Below 200 mg/dL.

What ratio of HDL to LDL is considered healthy?

Higher HDL and lower LDL levels are ideal.

How can HDL levels be increased?

Through exercise, healthy diet, and reduced intake of saturated fats.

What are cholesterol esters?

Storage forms of cholesterol where the hydroxyl group is esterified with a fatty acid.

Where are cholesterol esters found?

In the core of lipoproteins.

What is lipid metabolism?

The process of synthesis, transport, and degradation of lipids in the body.

What are the major pathways of lipid metabolism?

Lipogenesis, lipolysis, and β-oxidation.

What is lipogenesis?

The synthesis of fatty acids and triacylglycerols for storage.

What is lipolysis?

The breakdown of stored triacylglycerols into fatty acids and glycerol.

What is β-oxidation?

The catabolic process that breaks down fatty acids to produce acetyl-CoA, NADH, and FADH₂.

Where does β-oxidation occur?

In the mitochondria.

What is the fate of acetyl-CoA from β-oxidation?

It enters the citric acid cycle for ATP production.

What are ketone bodies?

Compounds produced from excess acetyl-CoA during fat metabolism.

When are ketone bodies formed?

During fasting, prolonged exercise, or low-carbohydrate diets.

What are examples of ketone bodies?

Acetoacetate, β-hydroxybutyrate, and acetone.

What condition results from excessive ketone body accumulation?

Ketosis or ketoacidosis.