Overview
This lecture covers the basics of chemical reactions, acids and bases, pH, electrolytes, and the difference between inorganic and organic compounds, with an introduction to the four classes of organic molecules.
Chemical Reactions: Basics
- Chemical reactions involve the formation or breaking of bonds between atoms or molecules.
- Reactants are substances changed by a reaction; products are substances formed.
- Reactions can proceed in both directions (are reversible).
- Synthesis reactions build larger molecules from smaller ones (anabolism).
- Decomposition reactions break down larger molecules into smaller ones (catabolism).
- Exchange reactions involve breaking down molecules and rearranging their parts.
pH, Acids, Bases, and Buffers
- The pH scale (0-14) measures hydrogen ion concentration; lower pH is more acidic, higher pH is more basic.
- Each whole number change in pH represents a tenfold change in hydrogen ion concentration.
- Acids release hydrogen ions (H+) in water; bases release hydroxyl ions (OH–).
- Buffers are chemicals that help resist changes in pH by accepting or donating hydrogen ions.
Electrolytes and Inorganic Compounds
- Electrolytes are substances that release ions in water and conduct electricity.
- Inorganic compounds include water, oxygen, carbon dioxide, and salts (minerals).
- Water is a universal solvent, polar, and essential for metabolic reactions and transport.
- Oxygen is used in cellular respiration to produce ATP (energy).
- Carbon dioxide is a waste product of cellular respiration.
- Inorganic salts (e.g., NaCl, K+, Ca2+, Mg2+) are important electrolytes for body processes.
Organic Compounds
- Organic compounds contain carbon atoms covalently bonded with hydrogen and often oxygen and nitrogen.
- Carbon forms four covalent bonds, creating long chains or rings.
- The four main classes of organic molecules: carbohydrates, lipids, proteins, nucleic acids.
Key Terms & Definitions
- Reactant — Substance changed during a chemical reaction.
- Product — Substance formed by a chemical reaction.
- Synthesis Reaction (Anabolism) — Reaction building larger molecules from smaller units.
- Decomposition Reaction (Catabolism) — Reaction breaking down larger molecules into smaller units.
- Exchange Reaction — Reaction rearranging atoms/molecules between compounds.
- pH — Measure of hydrogen ion concentration in solution.
- Acid — Substance releasing hydrogen ions in water.
- Base — Substance releasing hydroxyl ions in water.
- Buffer — Chemical that resists changes in pH.
- Electrolyte — Substance releasing ions in water, conducting electricity.
- Organic Compound — Compound containing carbon and hydrogen, often oxygen/nitrogen.
Action Items / Next Steps
- Identify the four classes of organic molecules in your textbook (carbohydrates, lipids, proteins, nucleic acids).
- Note key functions, examples, and basic structures (building blocks) of each organic class.
- Complete textbook reading and accompanying student guide for this chapter.
- Prepare notes on organic molecules for an upcoming class activity.