Metabolism, catabolism and chemical reaction

Metabolism Overview

  • Definition: Metabolism is a property of life that arises from molecular interactions in a cell's organized environment.

  • Cellular Functions: Functions like a miniature chemical industry with thousands of reactions occurring concurrently.

  • Molecule Interconversion: Sugars can be converted into amino acids and vice versa; small molecules assemble into polymers that can be broken down as needed.

  • Process Coordination: Metabolic processes are highly coordinated allowing cells to adapt, grow, and respond to changes.

Energy Generation and Utilization

  • ATP Production: Cells generate ATP by breaking down organic molecules to fuel cellular activities, including growth, cell division, contraction, and secretion.

  • Functions of Metabolism:

    • Provides energy for cellular activities.

    • Maintains homeostasis.

    • Supports metabolic turnover (recycling molecules).

    • Drives specialized processes like secretion and muscle contraction.

Components of Cellular Metabolism

  • Organic Molecules: Amino acids, lipids, and simple sugars constitute the nutrient pool utilized in metabolism.

  • Catabolism vs. Anabolism:

    • Catabolism: The breakdown of larger molecules releases energy (ATP) during processes such as glycolysis and the TCA cycle.

    • Anabolism: The synthesis of larger molecules from smaller units requires energy; essential for growth and maintenance.

Mitochondrial Function

  • Relationship with Mitochondria: Cells supply mitochondria with pyruvic acid and acetyl CoA, which are derived from larger molecules' breakdown.

  • Energy Generation: Mitochondria generate ATP using the two pathways:

    1. TCA Cycle: Breakdown of acetyl CoA into CO2 while generating electron carriers.

    2. Electron Transport System (ETS): Energy released from electron transfers is used to form an electrochemical gradient.

Tissue-Specific Functions

  • Liver: Regulates metabolism, blood glucose levels, and nutrient processing.

  • Adipose Tissue: Stores energy as triglycerides and releases fatty acids during fasting.

  • Skeletal Muscle: Holds glycogen reserves for energy.

  • Neural Tissue: Requires a constant glucose supply for proper function.

  • Peripheral Tissues: Metabolize nutrients under hormonal control.

Energy and Biological Work

  • Energy Sources: Cells derive energy from nutrients, which is stored in chemical bonds and converted to ATP for cellular functions.

  • Types of Cellular Work: Includes mechanical tasks, chemical synthesis, and transport operations (moving ions/molecules across membranes).

Thermodynamics in Metabolism

  • First Law: Energy cannot be created or destroyed, only transformed.

  • Second Law (Entropy): Energy transformations increase disorder; cells maintain order by expending energy.

Energy Measurement

  • Units of Energy:

    • Calorie: Heat required to raise 1g of water by 1°C.

    • Joule (J): SI unit of energy; amount of work done.

    • Kilocalorie (kcal): Used for food energy; 1 kcal = 1000 cal.

  • ATP Units: Energy released from ATP hydrolysis (~30.5 kJ/mol).

Types of Metabolic Reactions

  • Anabolism: Formation of larger molecules from smaller ones; requires energy.

  • Catabolism: Breakdown of larger molecules into smaller units; releases energy.

Chemical Reaction Dynamics

  • Chemical Bonds and Energy: Free energy (energy available to do work) influences reaction spontaneity and rates.

  • Dynamic Equilibrium: Achieved when the forward and reverse reaction rates are balanced, maintaining reactant and product concentrations.

Redox Reactions and Electron Carriers

  • Oxidation-Reduction: Oxidation involves electron loss; reduction involves electron gain; important in metabolism.

  • Electron Carriers: Facilitate electron transfer during metabolic processes.

Enzymes and Catalysis

  • Definition of Enzymes: Biological catalysts that accelerate reactions without permanent alteration.

  • Enzyme-Substrate Dynamics: Enzymes bind specific substrates, forming an unstable enzyme-substrate complex, which subsequently produces reaction products.

Enzyme Activation and Specificity

  • Cofactors: Many enzymes require cofactors (organic or inorganic) to function.

  • Optimal Conditions: Enzymes function best at specific temperatures and pH levels; extreme conditions can denature them.

Regulation of Metabolism

  • Compartmentation: Enzymes are localized within specific cellular compartments to control reaction rates effectively.

  • Feedback Inhibition: The final product of a metabolic pathway can inhibit an earlier enzyme, regulating the pathway.

Nutrient Metabolism Significance

  • Role of Enzymes in Development: Enzyme concentrations are strategically high during growth phases, ensuring smooth biochemical functions.

  • Disruption Effects: Poisoning or exposure can impair enzyme functions, affecting overall cellular operations.