Metabolic Pathways Overview

Metabolic Pathways

• Definition: Series of biochemical reactions that convert a substrate into a product within a cell, involving various enzymes.

• Types of Metabolic Pathways:

  1. Catabolic Pathways:

     • Break down molecules to produce energy (ATP).
     • Example: Glycolysis, Citric Acid Cycle (Krebs Cycle).

  2. Anabolic Pathways:

     • Build complex molecules from simpler ones, requiring energy.
     • Example: Protein synthesis, Glycogenesis.

• Key Metabolic Pathways:

  1. Glycolysis:

     • Breakdown of glucose into pyruvate.
     • Occurs in the cytoplasm; net gain of 2 ATP.

  2. Citric Acid Cycle (Krebs Cycle):

     • Completes the oxidation of substrates derived from glycolysis.
     • Produces NADH, FADH2, and ATP; occurs in the mitochondria.

  3. Oxidative Phosphorylation:

     • Uses electrons from NADH and FADH2 to generate ATP via the electron transport chain.
     • Involves chemiosmosis and occurs in the inner mitochondrial membrane.

  4. Photosynthesis (for plants):

     • Converts light energy into chemical energy.
     • Occurs in chloroplasts; involves light-dependent and light-independent reactions (Calvin Cycle).

• Regulation of Metabolic Pathways:

  • Enzyme activity modulation through:
    • Allosteric regulation: Enzymes change shape upon substrate binding.
    • Feedback inhibition: End products inhibit early steps (e.g., ATP inhibiting phosphofructokinase in glycolysis).

• Metabolic Disorders:

  • Result from enzyme deficiencies (e.g., phenylketonuria from phenylalanine hydroxylase deficiency).
  • Can lead to accumulation of substrates or deficits in products.

• Importance of Metabolic Pathways:

  • Energy production for cellular functions.
  • Synthesis of biomolecules necessary for growth and maintenance.
  • Integration of various metabolic processes to maintain homeostasis.

Metabolic Pathways

• Series of biochemical reactions converting substrates into products, involving enzymes.

Types of Metabolic Pathways

• Catabolic Pathways:

  • Decompose molecules to release energy in the form of ATP.
  • Examples include glycolysis and the citric acid cycle (Krebs cycle).

• Anabolic Pathways:

  • Synthesize complex molecules from simpler ones, consuming energy.
  • Examples include protein synthesis and glycogenesis.

Key Metabolic Pathways

• Glycolysis:

  • Converts glucose into pyruvate.
  • Occurs in the cytoplasm, yielding a net gain of 2 ATP.

• Citric Acid Cycle (Krebs Cycle):

  • Finalizes the oxidation of substrates from glycolysis.
  • Produces NADH, FADH2, and ATP, taking place in the mitochondria.

• Oxidative Phosphorylation:

  • Utilizes electrons from NADH and FADH2 to generate ATP along the electron transport chain.
  • Involves chemiosmosis and occurs in the inner mitochondrial membrane.

• Photosynthesis (in plants):

  • Transforms light energy into chemical energy.
  • Occurs in chloroplasts; comprises light-dependent and light-independent reactions (Calvin Cycle).

Regulation of Metabolic Pathways

• Modulated through:
  • Allosteric Regulation: Enzymes alter shape when substrates bind.
  • Feedback Inhibition: End products inhibit earlier steps, such as ATP inhibiting phosphofructokinase during glycolysis.

Metabolic Disorders

• Arise from enzyme deficiencies (e.g., phenylketonuria due to a deficiency of phenylalanine hydroxylase).
• Can cause substrate accumulation or product deficits.

Importance of Metabolic Pathways

• Essential for energy production to support cellular functions.
• Facilitate biosynthesis of necessary biomolecules for growth and maintenance.
• Ensure integration of various metabolic processes to uphold homeostasis.