Biochemistry: Fatty Acid Oxidation

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Questions and Answers

What is the role of bile salts in lipid digestion?

They convert lipids into water-soluble forms immediately.

They hydrolyze triglycerides into fatty acids.

They emulsify lipids to enhance enzyme access. (correct)

They absorb lipids directly into the bloodstream.

What is formed during the emulsification of triglycerides by bile salts?

Large lipid droplets suspended in water.

Fatty acids and cholesterol only.

Mixed micelles including lipids and bile salts. (correct)

Glycerol and water-soluble fatty acids.

What happens to bile salts during the absorption of lipids?

They are absorbed along with fatty acids.

They remain in the intestinal mucosa.

They are converted into fatty acids and glycerol.

They dissociate from micelles and stay in the lumen. (correct)

What results from a blockage in the biliary duct?

Steatorrhoea characterized by pale, bulky stools. Signup and view all the answers

Which component is NOT typically found in a mixed micelle during lipid absorption?

Triglycerides Signup and view all the answers

What is a primary role of fatty acids and their derivatives in biological systems?

They are used for high energy storage. Signup and view all the answers

Which class of lipids is characterized by the presence of glycerol and fatty acids?

Esters of fatty acids and glycerol Signup and view all the answers

Why are lipids effective insulators in biological systems?

Their hydrophobic nature reduces heat exchange. Signup and view all the answers

What is the classification basis for lipids compared to other biomolecules?

Physical properties, especially solubility in organic solvents Signup and view all the answers

Which of the following is a common use of lipids in humans?

For protection against loss of moisture Signup and view all the answers

Which group of lipids acts as signaling molecules?

Steroid hormones Signup and view all the answers

What is a characteristic of triglycerides compared to glycogen?

They store more energy per weight. Signup and view all the answers

Which of the following vitamins is fat-soluble?

Vitamin D Signup and view all the answers

What is the total ATP yield from the complete oxidation of one molecule of Palmitoyl-CoA?

130 ATP Signup and view all the answers

How many ATP are generated per carbon atom oxidized from Palmitic acid?

8.1 Signup and view all the answers

What is the first step in the oxidation of odd-numbered fatty acids?

Activation to fatty acyl-CoA Signup and view all the answers

What compound must be further catabolized after oxidation to enter the citric acid cycle?

Propionyl-CoA Signup and view all the answers

Which enzyme is involved in the final oxidation of propionyl-CoA?

Mutase Signup and view all the answers

What happens when there is a defect in mutase activity concerning propionyl-CoA metabolism?

Methylmalonyl-CoA concentrations increase Signup and view all the answers

What is the significance of reduced flavoproteins (FAD) in ATP generation during fatty acid oxidation?

Each FAD yields 2 ATP through electron transport Signup and view all the answers

What is the primary reason for the higher energy yield from fatty acid oxidation compared to carbohydrate oxidation?

Higher number of carbons in fatty acids Signup and view all the answers

What percentage of dietary fat is constituted by triacylglycerides?

More than 90% Signup and view all the answers

Which of the following lipids are soluble in organic solvents?

All of the above Signup and view all the answers

How do bile salts facilitate lipid digestion?

By emulsifying fat to form micelles Signup and view all the answers

What is the role of the carboxyl group in bile acids?

It is often conjugated to form bile salts Signup and view all the answers

Which enzymes are involved in the digestion of emulsified lipids?

Pancreatic lipase Signup and view all the answers

What is a primary source of triacylglycerols for the body?

Dietary intake Signup and view all the answers

What structural feature gives bile salts their emulsifying properties?

A hydrophobic surface and a hydrophilic surface Signup and view all the answers

What is the significance of micelles formed by bile salts?

They allow digestive enzymes to effectively access lipids Signup and view all the answers

What is the primary site of triacylglycerol digestion?

Duodenum Signup and view all the answers

What enzyme is primarily responsible for hydrolysing triacylglycerol?

Pancreatic lipase Signup and view all the answers

Which component forms mixed micelles along with monoacylglycerols and fatty acids?

Bile salts Signup and view all the answers

What would likely occur in patients with an abnormally low concentration of bile salts?

Increased steatorrhoea Signup and view all the answers

What is a common cause of reduced bile salt concentration in the intestine?

Biliary obstruction Signup and view all the answers

What happens to fatty acids after absorption into intestinal epithelial cells?

They are re-esterified to form triacylglycerols. Signup and view all the answers

Which vitamins are notably at risk of deficiency in patients with low bile salt concentrations?

Vitamins A, D, E, and K Signup and view all the answers

What is the purpose of bile salt micelles in the digestion process?

To stabilize lipid molecules in water. Signup and view all the answers

Study Notes

Fatty Acid Oxidation

Palmitoyl-CoA (16 carbon fatty acid) degrades to 8 mol of acetyl-CoA.
Balanced equation for oxidation:
- Palmitoyl-CoA + 7CoA-SH + 7FAD + 7NAD+ + 7H2O → 8 acetyl-CoA + 7FADH2 + 7NADH + H+.
Each FADH2 produces 2 ATP and each NADH produces 3 ATP, totaling 35 ATP from reduced cofactors.
Oxidation of 8 acetyl-CoA through the TCA cycle yields 96 ATP.
Net ATP yield from one palmitic acid: 130 ATP (35 + 96 - 1 for activation).
ATP yield per carbon oxidized: approximately 8.1 (130/16).
For comparison, glucose yields 6 ATP per 6 carbons oxidized.

Odd-Numbered Fatty Acid Oxidation

Odd-numbered fatty acids are oxidized similarly to even-numbered, starting at the carboxyl end.
Final cycle features a 5-carbon acyl-CoA (Butyryl-CoA).
Cleavage yields acetyl-CoA (2C) and propionyl-CoA (3C).
Acetyl-CoA is fully oxidized; propionyl-CoA requires further catabolism.
Increased methylmalonyl-CoA due to defective mutase or vitamin B12 deficiency leads to severe acidosis.

Lipids Overview

Organic molecules, soluble in non-polar solvents, sparingly soluble in water.
Serve protective roles (moisture retention in birds, humans, camels).
Provide energy in diets through sources like oils and margarine.

Lipid Classes

Classified based on solubility:
- Fatty acids (saturated, unsaturated, eicosanoids).
- Esters of fatty acids and glycerol (triglycerides, phosphoglycerides).
- Lipids without glycerols (sphingolipids).
- Sterols (cholesterol, steroid hormones, vitamin D).
- Terpene and isoprenoid derivatives.

Functions of Lipids

Serve as high-energy storage, yielding 6 times more energy than glycogen.
Provide insulation and reduced heat exchange via adipose tissue.
Form hydrophobic barriers in cellular membranes.
Act as signaling molecules (prostaglandins, steroids) and enzyme cofactors.
Precursors to fat-soluble vitamins (A, D, E, K).

Lipid Digestion and Absorption

90% of dietary lipids are triglycerides (TAGs).
Digestion begins in the stomach but is limited due to aggregation.
Bile salts (detergent action) emulsify TAGs, aiding fat digestion.

Role of Bile Salts

Bile salts possess both hydrophobic and hydrophilic surfaces, allowing for emulsification at the oil-water interface.
Form micelles, facilitating digestion by water-soluble pancreatic lipases and absorption into intestinal mucosa.

Lipase Action

Lipases hydrolyze ester linkages in TAGs, producing monoacylglycerol and fatty acids.
Stable interaction with water is necessary for absorption.

Clinical Implications

Conditions such as biliary duct obstruction lead to steatorrhea (bulky, oily stools).
Inadequate bile salts affect absorption of fat-soluble vitamins, potentially leading to deficiencies.
Patients may require dietary modifications and vitamin supplementation through injection.

Post-Absorption

Inside intestinal epithelial cells, fatty acids are re-esterified into triglycerides after absorption.

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Description

This quiz covers the stages of fatty acid oxidation, focusing on the degradation of Palmitoyl-CoA to acetyl-CoA. It includes details about the balanced equation and the ATP yield from reduced flavoproteins and nucleotides. Test your understanding of metabolic pathways and energy production in biochemistry.