Chemistry Review Lecture

Introduction

• Understanding chemistry is essential for grasping how molecules interact in living beings.
• Metabolism and biochemistry involve numerous chemical reactions within cells.
• Focus on sodium chloride (table salt) as an example.
  • Composed of sodium (a toxic metal) and chlorine (a poisonous gas).
  • Forms an ionic compound, sodium chloride, which is safe to consume.

Chemical Bonds

• Chemical bonds form molecules when atoms interact, either by sharing or transferring electrons.
• *Types of Bonds:
  • Covalent Bonds:
    • Formed by sharing a pair of valence electrons.
    • Example: Two hydrogen atoms share electrons to form H2 (a single bond).
    • Double bonds involve sharing two pairs of electrons (e.g., oxygen molecules, O2).
  • Hydrogen Bonds:
    • Occur in polar molecules like water due to electronegativity differences.
    • Oxygen in H2O is more electronegative than hydrogen, leading to a polar molecule with partial charges.
    • Result in hydrogen bonds between water molecules.
  • Ionic Bonds:
    • Occur between oppositely charged ions (e.g., sodium chloride).
    • Sodium (positive) and chlorine (negative) form a stable ionic compound.***

Organic and Inorganic Compounds

• Organic Compounds:
  • Carbon-based molecules such as carbohydrates, fats, proteins, and nucleic acids.
• Inorganic Compounds:
  • Include water, salts, and certain acids/bases.
  • Water is crucial as it makes up 60-80% of cells and maintains homeostasis.

Properties of Water

• High Heat Capacity and Vaporization:
  • Requires substantial energy to change temperature or vaporize.
  • Aids in homeostasis by resisting temperature changes.
• Hydrophilic vs. Hydrophobic:
  • Hydrophilic substances (e.g., salts) dissolve easily in water.
  • Hydrophobic substances (e.g., oils) do not dissolve, leading to separation.
• Cohesion:
  • Water molecules stick together, aiding processes like plant water uptake.
  • High surface tension supports objects like water striders.
• Density of Ice:
  • Ice is less dense than water due to a specific crystal lattice, allowing it to float, which is ecologically important.

Carbon-Based Life

• Carbon's ability to form four stable bonds makes it versatile, leading to diverse compounds.
• Functional Groups:
  • Different properties arise from various attachments to carbon skeletons (e.g., amino and carboxy groups).

Macromolecules

• Types: Proteins, Carbohydrates, Lipids, Nucleic Acids
• Polymers and Monomers:
  • Polymers are chains of repeating monomers.
  • Example: Proteins are polypeptides formed from amino acid monomers.
• Polymerization and Hydrolysis:
  • Polymerization involves condensation reactions (water released when forming bonds).
  • Hydrolysis involves breaking bonds with water.

Conclusion

• This lecture provides foundational knowledge important for understanding biological chemistry.
• Upcoming lectures will delve deeper into carbohydrates and other macromolecules.