Unit 3: Lipid & Amino Acid Metabolism

February 20, 2026

Semester 2
BP203T

Introduction to Lipid & Amino Acid Metabolism

Unit 3 covers the breakdown and synthesis of fats and amino acids. It explains how fatty acids are burned for energy (Beta-Oxidation), why ketone bodies form in Diabetes (Ketoacidosis), and the complete Urea Cycle for nitrogen disposal. It also covers metabolic disorders like PKU, Albinism, and the biochemical basis of neurotransmitter synthesis.
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Syllabus & Topics

  • 1Lipid Metabolism: Beta-Oxidation of saturated fatty acid (Palmitic acid – 16C): Complete pathway and energy yield.
  • 2Formation and utilization of Ketone bodies (Acetoacetate, Beta-hydroxybutyrate, Acetone).
  • 3Ketoacidosis: Mechanism and clinical significance (in Diabetes).
  • 4De novo synthesis of fatty acids: Palmitate synthesis pathway.
  • 5Biological significance of Cholesterol.
  • 6Conversion of Cholesterol into Bile acids, Steroid hormones, and Vitamin D.
  • 7Disorders of lipid metabolism: Hypercholesterolemia, Atherosclerosis, Fatty Liver, and Obesity.
  • 8Amino Acid Metabolism: General reactions – Transamination, Deamination, and Decarboxylation.
  • 9Urea Cycle: Complete pathway, enzymes, and disorders (Hyperammonemia).
  • 10Catabolism of Phenylalanine and Tyrosine.
  • 11Metabolic disorders: Phenylketonuria (PKU), Albinism, Alkaptonuria, Tyrosinemia.
  • 12Synthesis and significance of biological substances: 5-HT (Serotonin), Melatonin, Dopamine, Noradrenaline, Adrenaline.
  • 13Catabolism of Heme.
  • 14Hyperbilirubinemia and Jaundice: Types (Pre-hepatic, Hepatic, Post-hepatic).

Learning Objectives

Calculate Beta-Oxidation Yield: Calculate the total ATP produced from complete oxidation of Palmitic acid.
Explain Ketoacidosis: Describe why ketone bodies accumulate in uncontrolled Type 1 Diabetes.
Draw Urea Cycle: Write the urea cycle with its 5 key reactions and enzymes.
Understand PKU: Explain the enzyme deficiency in PKU and why Phenylalanine accumulates.
Trace Catecholamine Synthesis: Write the biosynthetic pathway from Tyrosine to Adrenaline.

Frequently Asked Questions (FAQs)

Q1. How many ATP are produced from one Palmitic acid (16C)?

Complete β-oxidation of palmitic acid (16 carbons) produces:

  • 7 FADH₂

  • 7 NADH

  • 8 Acetyl-CoA

After oxidation in the TCA cycle and oxidative phosphorylation, the total ATP yield is approximately 106 ATP.

Q2. What are Ketone Bodies and when are they produced?

Ketone bodies include acetoacetate, β-hydroxybutyrate, and acetone. They are produced in the liver when fat breakdown exceeds carbohydrate metabolism, such as during diabetes mellitus, prolonged fasting, or starvation.

Q3. What is Phenylketonuria (PKU)?

Phenylketonuria (PKU) is a genetic disorder caused by deficiency of the enzyme phenylalanine hydroxylase, which normally converts phenylalanine to tyrosine. Accumulation of phenylalanine and its toxic metabolites can lead to intellectual disability.
Treatment: A low-phenylalanine diet.

Q4. What is the role of the Urea Cycle?

The urea cycle converts toxic ammonia (NH₃), produced during amino acid metabolism, into non-toxic urea, which is excreted in the urine.

Q5. What is the biochemical basis of Jaundice?

Jaundice occurs due to accumulation of bilirubin (a product of heme breakdown) in the blood and tissues. It can be classified as:

  • Pre-hepatic – Excess RBC destruction

  • Hepatic – Liver dysfunction

  • Post-hepatic – Obstruction of bile ducts