lipids

Question 1

What are lipids?

Answer 1

A chemically diverse group of compounds that are insoluble in water but soluble in non-polar organic solvents, often related to fatty acids.

Question 2

What is the general formula for fatty acids?

Answer 2

CH₃(CH₂)nCOOH, where n represents the number of carbon atoms in the hydrocarbon chain.

Question 3

How do fatty acids differ in structure?

Answer 3

hey can differ in chain length, number of double bonds (saturated, monounsaturated, polyunsaturated), position of double bonds, and type of double bond (cis or trans).

Question 4

What are the major biological roles of fatty acids?

Answer 4

Energy storage, protection/insulation, essential components of biological membranes, and precursors for bioactive molecules like eicosanoids.

Question 5

What is triacylglycerol (TAG)?

Answer 5

Esters of 3 fatty acids with glycerol, primarily used for energy storage in adipose tissue.

Question 6

What are phospholipids?

Answer 6

Esters of 2 fatty acids with glycerol, where the third carbon of glycerol is attached to a phosphate group and often another alcohol containing nitrogen.

Question 7

How are fatty acids named?

Answer 7

y their number of carbons and double bonds, e.g., C18:2 for linoleic acid (18 carbons, 2 double bonds). They can also be named based on their position from the methyl end (omega notation), e.g., ω-6 for linoleic acid.

Question 8

What are essential fatty acids?

Answer 8

Fatty acids that the body cannot synthesize (like linoleic acid and α-linolenic acid) and must be obtained through the diet.

Question 9

How are fatty acids synthesized in animals?

Answer 9

Fatty acid synthesis starts with acetyl-CoA and is catalyzed by enzymes like acetyl-CoA carboxylase and fatty acid synthase, producing palmitic acid (C16:0) as the primary product.

Question 10

What is the role of acetyl-CoA in fatty acid synthesis?

Answer 10

Acetyl-CoA is the precursor for fatty acid synthesis, converted to malonyl-CoA, which is used to elongate the carbon chain in fatty acids.

Question 11

What is β-oxidation?

Answer 11

The metabolic process by which fatty acids are broken down into acetyl-CoA units in the mitochondria, producing energy in the form of ATP.

Question 12

What is the key enzyme in the β-oxidation of fatty acids?

Answer 12

Acyl-CoA dehydrogenase, which catalyzes the initial step of β-oxidation by introducing a double bond in the fatty acid chain.

Question 13

What is the role of lipoproteins in lipid transport?

Answer 13

Lipoproteins transport lipids (such as TAG, phospholipids, and cholesterol) in the blood, including chylomicrons, VLDL, IDL, LDL, and HDL.

Question 14

What are chylomicrons?

Answer 14

Lipoproteins that transport dietary lipids from the intestines to peripheral tissues and the liver, composed primarily of TAG.

Question 15

What are the exogenous and endogenous pathways of lipid transport?

Answer 15

Exogenous pathway: Involves transport of dietary lipids via chylomicrons.
Endogenous pathway: Involves transport of lipids synthesized in the liver via VLDL, which are converted to LDL.

Question 16

What is the function of lipoprotein lipase (LPL)?

Answer 16

LPL hydrolyzes TAG in lipoproteins like chylomicrons and VLDL, releasing fatty acids that can be used by tissues for energy or stored.

Question 17

What is reverse cholesterol transport?

Answer 17

The process by which HDL particles collect excess cholesterol from peripheral tissues and transport it back to the liver for excretion.

Question 18

How do apolipoproteins function in lipid metabolism?

Answer 18

Apolipoproteins serve structural roles, activate/inhibit enzymes like lipoprotein lipase, and help receptors recognize lipoproteins for uptake.

Question 19

How does fatty acid metabolism differ in adipose tissue, liver, and muscle?

Answer 19

Adipose tissue: Stores fatty acids as TAG and releases NEFA into the bloodstream.
Liver: Synthesizes and metabolizes fatty acids, forming VLDL for lipid transport.
Muscle: Uses fatty acids for energy via β-oxidation.

Question 20

What is the role of carnitine in fatty acid oxidation?

Answer 20

Carnitine helps transport long-chain acyl-CoA molecules into the mitochondria for β-oxidation.

Question 21

What is the role of fatty acid synthase in fatty acid synthesis?

Answer 21

Fatty acid synthase is a multifunctional enzyme complex that catalyzes the elongation of fatty acids, adding 2-carbon units to form palmitic acid (C16:0).

Question 22

How do animals synthesize fatty acids like oleic acid (C18:1)?

Answer 22

Animals can elongate palmitic acid (C16:0) to stearic acid (C18:0) and then desaturate it to form oleic acid (C18:1).

Question 23

How does the fatty acid synthesis pathway differ between prokaryotes and eukaryotes?

Answer 23

In prokaryotes, fatty acid synthesis involves separate enzymes, while in eukaryotes, a multifunctional enzyme complex (fatty acid synthase) is involved.

Question 24

What is the role of phosphatidate in the synthesis of triacylglycerol and phospholipids?

Answer 24

Phosphatidate is a key intermediate in both triacylglycerol and phospholipid synthesis. It is converted into diacylglycerol or CDP-diacylglycerol, which are further modified to form these lipids.

Question 25

What are the key components of a lipoprotein particle?

Answer 25

Lipoproteins consist of a core containing TAG and cholesterol esters, surrounded by a phospholipid monolayer, with apolipoproteins attached to the surface.