Overview
This lecture provides a foundational review of basic chemistry concepts essential for understanding molecules and their role in microbiology, with a focus on biological macromolecules and their properties.
Atoms & Molecules
- Atoms are the basic units of matter, composed of protons (positive), neutrons (neutral), and electrons (negative).
- Protons and neutrons are located in the nucleus; electrons orbit the nucleus.
- An element consists of only one type of atom.
- Molecules are formed when atoms bond together; compounds are molecules containing at least two different elements.
Chemical Bonds
- Ionic bonds occur when atoms transfer electrons, forming cations (positive) and anions (negative) that attract each other.
- Covalent bonds involve atoms sharing electrons to form molecules.
- Organic molecules have carbon covalently bonded to hydrogen; inorganic molecules lack this bond.
- Nonpolar covalent bonds share electrons evenly; polar covalent bonds have uneven electron sharing, creating charged ends (poles).
Properties of Water & Hydrogen Bonding
- Polarity in water leads to the formation of hydrogen bonds between molecules.
- Hydrogen bonds are weak, breakable attractions between slightly positive (hydrogen) and slightly negative (oxygen) regions in water molecules.
- Water serves as a solvent and displays properties like surface tension and high specific heat due to hydrogen bonding.
pH and Solutions
- pH measures the concentration of hydrogen ions (H+) in an aqueous solution.
- Pure water has a neutral pH of 7; acids have pH < 7 (more H+), and bases have pH > 7 (less H+).
- Adding acid increases H+ (lowers pH), adding base decreases H+ (raises pH).
Biological Macromolecules
Proteins
- Proteins are organic compounds made of amino acids linked by peptide bonds (contain C, H, O, N).
- Functions: enzymes (catalysts), structure, movement, membrane transport, gene expression.
- Proteins can be hydrophilic, hydrophobic, or have both regions.
Carbohydrates
- Carbohydrates are organic, generally hydrophilic molecules made of C, H, and O.
- Monosaccharides (single sugars) include glucose, galactose, and fructose.
- Disaccharides are two monosaccharides linked (e.g., sucrose, lactose, maltose).
- Polysaccharides are long chains (e.g., glycogen, starch, cellulose).
- Major functions: energy storage, structural roles, and as part of nucleic acids.
Lipids
- Lipids are organic, largely hydrophobic molecules containing C, H, O, and sometimes P.
- Types include fats, oils, waxes, and phospholipids.
- Functions: energy storage (more efficient than carbohydrates), membrane structure (phospholipid bilayer), insulation.
- Cell membranes are primarily composed of a phospholipid bilayer with proteins and carbohydrate chains.
Nucleic Acids
- Nucleic acids (DNA & RNA) store and transmit genetic information.
- Built from nucleotides.
- DNA: double-stranded, bases are A, T, C, G with complementary base pairing (A-T, C-G).
- RNA: usually single-stranded, bases are A, U, C, G (U = uracil replaces T).
Key Terms & Definitions
- Atom — Basic unit of matter with protons, neutrons, and electrons.
- Element — Substance made of only one type of atom.
- Molecule — Group of atoms bonded together.
- Compound — Molecule containing two or more different elements.
- Ion — Atom or molecule with a charge due to electron loss/gain.
- Cation — Positively charged ion.
- Anion — Negatively charged ion.
- Ionic bond — Attraction between oppositely charged ions.
- Covalent bond — Bond formed by sharing electrons.
- Polar/nonpolar — Uneven/even sharing of electrons in a bond.
- Hydrogen bond — Weak attraction between polar molecules.
- pH — Measure of hydrogen ion concentration in a solution.
- Aqueous — Water-based solution.
- Protein — Polymer of amino acids; performs various cellular functions.
- Carbohydrate — Organic molecules for energy/storage, structure.
- Lipid — Hydrophobic organic molecule; stores energy, forms membranes.
- Nucleic acid — Polymer of nucleotides; carries genetic information.
Action Items / Next Steps
- Review basic chemistry concepts, focusing on atomic structure and bonding.
- Study the four major classes of organic macromolecules: proteins, carbohydrates, lipids, and nucleic acids.
- Ensure familiarity with pH and its biological relevance.