Overview
This lecture covers the basics of biochemistry, focusing on the differences between organic and inorganic compounds, their properties, and the main classes of biomolecules essential to life.
Organic vs. Inorganic Compounds
- Inorganic compounds do not contain carbon; examples: water, salts, acids, bases.
- Organic compounds contain carbon and are usually large and covalently bonded; examples: carbohydrates, lipids, proteins, nucleic acids.
- Carbon forms four covalent bonds and is considered electroneutral (shares electrons, does not gain/lose them).
Inorganic Compounds
- Water is the most abundant inorganic compound in the body (60–80% of body volume).
- Key properties of water: high heat capacity, high heat of vaporization, polar solvent, reactivity, and cushioning.
- Salts are ionic compounds that dissociate into cations and anions in water; important for body functions (electrolytes).
- Acids are proton (H⁺) donors; bases are proton acceptors (release OH⁻).
- The pH scale measures hydrogen ion concentration; below 7 is acidic, 7 is neutral, above 7 is basic (alkaline).
Organic Compounds: Carbohydrates
- Carbohydrates are sugars and starches (contain carbon).
- Three classes: monosaccharides (one sugar, monomer), disaccharides (two sugars), polysaccharides (many sugars, polymer).
- Examples: glucose (monosaccharide), sucrose (disaccharide), glycogen (polysaccharide).
Organic Compounds: Lipids
- Lipids (fats) are insoluble in water; main types: triglycerides, phospholipids, and steroids.
- Triglycerides: three fatty acids + glycerol; store energy, provide insulation and protection.
- Saturated fatty acids: single bonds, solid at room temp; unsaturated: double bonds, liquid at room temp.
- Phospholipids: glycerol, two fatty acids, phosphorus head (hydrophilic head, hydrophobic tail); form cell membranes.
- Steroids have four interlocking rings; cholesterol is the main example, important for membranes and hormone synthesis.
Organic Compounds: Proteins
- Proteins are polymers of amino acids (monomers) linked by peptide bonds.
- Four levels of protein structure: primary (amino acid sequence), secondary (alpha helix/beta sheet), tertiary (folded shape), quaternary (multiple chains).
- Fibrous proteins provide structure; globular proteins are functional (e.g., enzymes, antibodies).
- Denaturation (loss of shape) in proteins can be caused by changes in pH or temperature and may be irreversible.
Enzymes
- Enzymes are globular proteins that catalyze (speed up) chemical reactions without being consumed.
- Each enzyme acts on a specific substrate, lowering activation energy.
- Enzyme action: substrate binds, rearrangement occurs, products released.
Organic Compounds: Nucleic Acids
- Nucleic acids (DNA, RNA) are polymers of nucleotides (monomers).
- DNA is double-stranded with deoxyribose sugar; bases: A-T, G-C.
- RNA is single-stranded with ribose sugar; uracil replaces thymine.
ATP (Adenosine Triphosphate)
- ATP directly powers cellular reactions and provides immediate energy for cellular work (transport, mechanical, chemical).
Key Terms & Definitions
- Covalent bond — a chemical bond where atoms share electrons.
- Inorganic compound — a compound that does not contain carbon.
- Organic compound — a compound that contains carbon.
- Monomer — a small building-block molecule.
- Polymer — a long chain of monomers.
- Electrolyte — ions in solution that can conduct electricity.
- Peptide bond — the bond between amino acids in a protein.
- Denaturation — loss of protein shape and function due to environmental changes.
- Enzyme — a protein that speeds up chemical reactions.
- Nucleotide — monomer of nucleic acids.
Action Items / Next Steps
- Review the properties and roles of water, salts, acids, and bases.
- Study the structure and functions of carbohydrates, lipids, proteins, and nucleic acids.
- Recommended: read the related tables in the textbook for more details on biomolecules.