Recording-2026-02-10T15:31:52.208Z

Metabolism and Energy Loss

  • Each metabolic step results in the loss of energy into the environment as heat.

Overview of Metabolism

  • Metabolism: All the chemical reactions that occur within living cells.
    • Chemical Reactions: Require energy and enzymes for the breakdown of essential nutrients, which can then be absorbed and utilized for sustenance.

Classification of Metabolic Pathways

  • Metabolic reactions are classified into two main groups:
    1. Catabolic Pathways
    • Definition: Pathways that break down large molecules into smaller units.
    • Key Feature: Energy is released as a byproduct during the breakdown process. Therefore, catabolic reactions are categorized as exergonic reactions (exa means releasing energy).
    • Energy Storage: The energy generated is stored as ATP (adenosine triphosphate).
    • Examples:
      • Proteins → Amino acids
      • Lipids → Fatty acids and glycerol
      • Carbohydrates → Simple sugars
    1. Anabolic Pathways
    • Definition: Pathways that require energy to construct larger molecules from smaller units.
    • Energy Source: Utilizes stored energy from ATP.
    • Key Feature: Absorbs energy during the reaction, known as endergonic reactions.
    • Example: Protein synthesis involves converting DNA to RNA, and then RNA is used to synthesize proteins.

Chemical Reactions and Enzymes

  • Chemical Reactions: Depend on enzymes, which are biological catalysts that facilitate these reactions.
    • Redox Reactions: Include oxidation and reduction processes essential for metabolism.
    • Oxidation: The loss of electrons from a molecule. The molecule that loses electrons becomes oxidized.
    • Reduction: The gain of electrons by a molecule. The molecule that accepts electrons becomes reduced.
  • Electron Carriers: Facilitate electron transfer during metabolic processes. Common carriers in biological systems include:
    • NAD (Nicotinamide adenine dinucleotide)
    • NADP (Nicotinamide adenine dinucleotide phosphate)
    • FAD (Flavin adenine dinucleotide)

Role of Enzymes

  • Enzymes Defined: Biological catalysts that accelerate chemical reactions by lowering the activation energy needed.
    • Activation Energy: The energy required to start a reaction.
    • Chemical reactions occur more rapidly in the presence of enzymes compared to in their absence due to lower initial energy requirements.
    • Enzyme Classification: Six different groups based on their functions:
    1. **Hydrol