BIOCHEICAL-ENERGY-PRODUCTION

Metabolism Overview

  • Definition: Sum total of all chemical reactions in a living organism.

  • Importance:

    • Source of energy for bodily functions.

    • Essential for cellular processes like protein synthesis, DNA replication, RNA transcription, and membrane transport.

Chapter Outline

  • 23.1 Metabolism

  • 23.2 Metabolism and Cell Structure

  • 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways

  • 23.4 Important Carboxylate Ions in Metabolic Pathways

  • 23.5 High-Energy Phosphate Compounds

  • 23.6 Overview of Biochemical Energy Production

  • 23.7 The Citric Acid Cycle

  • 23.8 The Electron Transport Chain

  • 23.9 Oxidative Phosphorylation

  • 23.10 ATP Production for the Common Metabolic Pathway

  • 23.11 Non-ETC Oxygen-Consuming Reactions

  • 23.12 B Vitamins and the Common Metabolic Pathway

Subtypes of Metabolic Reactions

  • Catabolism:

    • Breakdown of large biochemical molecules into smaller ones.

    • Energy is usually released.

    • Example: Oxidation of glucose.

  • Anabolism:

    • Building larger biochemical molecules from smaller ones.

    • Requires energy.

    • Example: Protein synthesis.

Metabolic Pathways

  • Definition: A series of consecutive biochemical reactions converting a starting material into an end product.

  • Types of pathways:

    • Linear: Direct pathway.

    • Cyclic: Reactions recycle through a cycle.

  • Similarity: Major pathways are conserved across all forms of life.

Important Compounds in Metabolism

  • Adenosine Phosphates:

    • AMP (1 phosphate): Structural component of RNA.

    • ADP (2 phosphates): Key component in metabolic pathways.

    • ATP (3 phosphates): Main energy currency in metabolism.

  • Role of Nucleotide Triphosphates:

    • UTP (Carbohydrate metabolism).

    • GTP (Protein and carbohydrate metabolism).

    • CTP (Lipid metabolism).

Coenzymes in Metabolism

  • Flavin Adenine Dinucleotide (FAD):

    • Coenzyme in metabolic redox reactions.

    • Reduced form: FADH2, important for energy transfers.

  • Nicotinamide Adenine Dinucleotide (NAD):

    • Oxidized form (NAD+) and reduced form (NADH).

    • Serves as oxidizing agent in various reactions.

  • Coenzyme A:

    • Derived from vitamin B pantothenic acid, involved in various metabolic reactions.

High-Energy Phosphate Compounds

  • Definition: Compounds with higher free energy of hydrolysis than typical compounds.

  • Characteristics: Contain at least one strained bond (greater energy needed to break).

  • Importance: Energy for many biological reactions.

Energy Production Stages

  1. Digestion:

    • Begins in the mouth, continues in stomach and small intestine. Produces absorbable molecules - glucose, amino acids, fatty acids.

  2. Acetyl Group Formation:

    • Small molecules from digestion are further oxidized to produce acetyl-CoA and reduced NADH.

  3. Citric Acid Cycle:

    • Acetyl group oxidized to CO2 and energy; produces NADH and FADH2.

  4. Electron Transport Chain:

    • NADH and FADH2 transfer electrons to produce ATP via oxidative phosphorylation.

The Citric Acid Cycle

  • Definition: Series of reactions where acetyl CoA is oxidized to CO2, producing FADH2 and NADH.

  • Phases:

    1. Formation of citrate.

    2. Isocitrate formation.

    3. Oxidation of isocitrate into CO2.

    4. Formation of succinyl CoA.

    5. Regeneration of oxaloacetate.

  • Regulation: Controlled by ATP/ADP levels affecting enzyme activities.

The Electron Transport Chain (ETC)

  • Function: Transfers electrons from NADH and FADH2 via protein complexes to produce ATP and water.

  • Components:

    • Complexes I-IV and mobile carriers like coenzyme Q and cytochrome c.

  • Importance: Most oxygen consumed by cells is utilized here, leading to ATP synthesis.

Oxidative Phosphorylation

  • Definition: ATP synthesis from ADP using energy from the ETC.

  • Process: Proton gradient created across the inner mitochondrial membrane drives ATP synthesis via ATP synthase.

B Vitamins in Metabolism

  • Role: Modified forms function as coenzymes.

  • Key vitamins:

    • Niacin (NAD+), Riboflavin (FAD), Thiamin (TPP), Pantothenic Acid (CoA).

  • Importance: Necessary for utilization of energy from macronutrients.