Biological Reactions and Metabolism

Overview of Biological Reactions

  • Biological systems are based on foundational principles similar to math.
  • The building blocks of biology include macromolecules made from smaller units called polymers.

Polymers and Monomers

  • Polymers are formed by linking many smaller units called monomers.
  • Example: Nucleotide is a monomer of nucleic acids (RNA, DNA).
  • Linking monomers creates polymers through covalent bonds, which are strong due to shared electrons.

Covalent Bonds

  • Definition: Covalent bonds involve the sharing of electrons between atoms.
  • Characteristics:
    • Strong and stable.
    • Key in storing energy within macromolecules.

Types of Chemical Reactions

Condensation Reaction

  • Two monomers (with OH groups) bond together to form a dimer, releasing water.
  • This process forms a covalent bond between units.

Hydrolysis Reaction

  • The opposite of condensation.
  • Involves the addition of water to split molecules (e.g., breaking down sucrose into glucose and fructose).
  • Hydrolysis is a catabolic process.

Metabolism

  • Definition: All chemical reactions occurring in the body, including both breakdown and buildup of molecules.
  • Metabolism can be catabolic (breaking down, e.g., hydrolysis) or anabolic (building up, e.g., condensation).
  • Energy exchanges are central to metabolic processes:
    • Catabolic reactions release energy (exergonic).
    • Anabolic reactions require energy input (endergonic).

Energy in Biological Systems

  • Energy stored in chemical bonds can be released or utilized:
    • Released energy from broken bonds can perform work in cells.
    • ATP (adenosine triphosphate) is the main energy currency in cells.

Structure of ATP

  • Composed of adenine (a nucleotide), ribose (a sugar), and three phosphate groups.
  • High-energy bonds between phosphates store energy, which is released during hydrolysis.
  • ATP acts as a carrier of stored energy for cellular processes.

Thermodynamics in Reaction Dynamics

First Law of Thermodynamics

  • Energy cannot be created or destroyed; it only changes form.

Second Law of Thermodynamics

  • With each reaction, entropy (disorder) increases, making some energy less usable.

Potential and Kinetic Energy

  • Stored energy (potential energy) can be transformed into energy of motion (kinetic energy).
  • Example: Sledding down a hill, where a push (activation energy) allows motion.

Summary of Reactions

  • Catabolic Reactions:

    • Break down larger molecules, release stored energy, include hydrolysis.
    • Example: Digestion of food releases energy for use.

  • Anabolic Reactions:

    • Build larger molecules from smaller units, require energy input, include condensation.
    • Example: Synthesis of proteins and nucleic acids.

Important Vocabulary

  • Condensation Reaction: Formation of a covalent bond releasing water.
  • Hydrolysis Reaction: Breakdown of a compound with water.
  • Catabolism: Breakdown processes releasing energy.
  • Anabolism: Building processes requiring energy.
  • ATP: Primary energy carrier in cells.
  • Exergonic Reactions: Release energy during reactions.
  • Endergonic Reactions: Require energy to proceed.