Fatty Acids, Lipoproteins, and Lipid Metabolism: Key Concepts for Biology and Biochemistry

What is the structure of a fatty acid?

A straight hydrocarbon chain with a carboxylic acid group (COOH) at one end.

What is the range of carbon atoms in fatty acids?

Fatty acids typically have 4 to 24 carbons.

What are saturated fatty acids?

Fatty acids where all carbon atoms are saturated with hydrogen and contain no double bonds.

What are monounsaturated fatty acids?

Fatty acids that contain one double bond (C=C).

What are polyunsaturated fatty acids?

Fatty acids that contain multiple double bonds (C=C).

What is hydrogenation?

The process of adding hydrogen to unsaturated fats to make them solid at room temperature.

What is the significance of essential fatty acids?

They are fatty acids that the body cannot synthesize and must be obtained from the diet.

Name two essential fatty acids.

Linoleic Acid (18:2ω6) and α-Linolenic Acid (18:3ω3).

What are eicosanoids?

Hormone-like substances that modulate various physiological functions such as blood pressure and immune response.

What are the main families of eicosanoids?

Prostacyclins, thromboxanes, leukotrienes, and prostaglandins.

What is the role of bile salts in lipid digestion?

Bile salts act as emulsifying agents that disperse fats in an aqueous solution, allowing lipase action.

What is the function of pancreatic lipase?

It hydrolyzes triglycerides into free fatty acids and glycerol in the small intestine.

What is a chylomicron?

A lipoprotein that transports exogenous triglycerides from the intestines to tissues.

What is the composition of chylomicrons?

They consist of triglycerides (~80%), phospholipids and cholesterol (~15%), and apoproteins (~1-2%).

What is the role of lipoprotein lipase (LPL)?

LPL hydrolyzes triglycerides to free fatty acids and glycerol, allowing their uptake by tissues.

What is the function of high-density lipoproteins (HDL)?

HDL removes cholesterol from non-hepatic tissues and transports it to the liver.

What is the rate-limiting enzyme in cholesterol synthesis?

HMG CoA reductase.

How does dietary cholesterol affect cholesterol synthesis?

Increased dietary cholesterol decreases synthesis, while decreased dietary cholesterol increases synthesis.

Where is cholesterol synthesized in the body?

Primarily in the liver and intestine, but almost all nucleated cells can synthesize cholesterol.

What is the size range of low-density lipoproteins (LDL)?

LDL particles are typically 20-25 nm in size.

What is the primary function of low-density lipoproteins (LDL)?

LDL delivers cholesterol to non-hepatic tissues via receptor-mediated endocytosis.

What happens to LDL after it binds to its receptor?

The LDL-receptor complex is internalized, leading to the release of cholesterol into the cell.

What is the importance of lecithin-cholesterol acyltransferase (LCAT)?

LCAT facilitates the transfer of cholesterol from cell membranes to HDL.

What is the primary component of very low-density lipoproteins (VLDL)?

VLDL primarily consists of triglycerides (~50%).

What is the function of intermediate density lipoprotein (IDL)?

IDL is formed from VLDL after triglyceride hydrolysis and is transient.

What is the role of apoproteins in lipoproteins?

Apoproteins help in the identification and function of lipoproteins in lipid transport.

What is the significance of the omega end in fatty acid nomenclature?

The omega end refers to the position of the first double bond from the methyl end of the fatty acid.

What is the difference between the alpha end and the omega end in fatty acids?

The alpha end (or delta end) is the carboxylic acid group (COOH), while the omega end is the methyl group (CH3).

What is the function of HDL?

Transports cholesterol from tissues to the liver.

What is the function of LDL?

Transports cholesterol from the liver to tissues.

What are the main components of bile?

82% water, 12% bile salts, 4% phospholipids, 0.7% free cholesterol, electrolytes, and bile pigments.

What is the primary function of bile?

Lipid emulsification and micelle formation.

How much bile is produced daily?

500-800 mL/day.

Where is bile synthesized?

In hepatocytes.

What happens to bile after synthesis?

It is sent to the gall bladder for concentration and storage.

What triggers the release of bile from the gall bladder?

Contraction of the gall bladder through the sphincter of Oddi into the duodenum.

What is the role of bile in cholesterol levels?

Increased bile excretion can lower cholesterol levels in the body.

What is the primary substrate for fatty acid synthesis?

Glucose.

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

They cannot cross the mitochondrial membrane; pyruvate and citrate can.

What is the function of fatty acid synthase?

It is a dimer of two identical polypeptide monomers involved in fatty acid synthesis.

Where does elongation and desaturation of fatty acids occur?

In the endoplasmic reticulum.

What are essential fatty acids?

Fatty acids that lack enzymes Δ12 and Δ15 desaturase, which add bonds past the Δ9 position.

What is the process of β-oxidation?

Breaking down long-chain fatty acids for energy.

What are ketone bodies produced from?

Acetyl CoA after β-oxidation.

What conditions lead to ketone production?

Starvation, low carbohydrate diets, and diabetes.

What is the role of leptin?

Reduces appetite, increases basal metabolic rate, and signals fullness to the brain.

What stimulates lipolysis in adipose tissue?

Glucagon.

What is the difference between brown adipose tissue (BAT) and white adipose tissue (WAT)?

BAT has more mitochondria and uncoupling protein I, which produces heat.

What is the effect of a high carbohydrate diet on lipid metabolism?

It downregulates β-oxidation and upregulates lipogenesis.

What happens during hyperglycemia?

Insulin production increases, promoting glucose uptake and storage via lipogenesis.

What is the role of insulin in lipid metabolism?

It promotes glucose uptake by adipocytes and storage of glucose via lipogenesis.

What is the function of adipose triglyceride lipase?

Stimulates lipolysis and release of triglycerides from adipose tissue.

What is the primary fuel source for muscles at rest?

Fat (via β-oxidation).

What is the process of esterification?

Formation of a triglyceride from glycerol and fatty acids.