Overview
This lecture covers the essential chemical elements and compounds of life, atomic structure, bonding, properties of water, macromolecules, and enzymes relevant for biology.
Essential Elements for Life
- Carbon, hydrogen, nitrogen, and oxygen make up 96% of living things.
- Phosphorus, calcium, sulfur, and potassium comprise most of the remaining 4%.
- Trace elements are required in very small amounts by organisms.
- Some elements are found only in soil and are rare in living organisms.
Atomic Structure and Bonds
- Atoms consist of protons (+), neutrons (neutral), and electrons (-).
- The atomic number equals the number of protons; atomic mass is protons plus neutrons.
- Isotopes differ in the number of neutrons; radioactive isotopes are unstable and emit energy.
- Valence electrons determine an atom’s reactivity.
- Ionic bonds involve the transfer of valence electrons; covalent bonds involve sharing them.
- Molecules are formed by covalent bonds; ions carry a net electrical charge.
Chemical Reactions
- Chemical reactions break and form bonds, producing new substances.
- Exothermic reactions release more energy than they absorb; endothermic do the opposite.
- Products are made from reactants during chemical reactions.
Properties of Water
- Water is the most abundant compound in living things.
- Water’s polarity results from slightly negative oxygen and slightly positive hydrogens.
- Cohesion is attraction among similar molecules; adhesion is attraction to different molecules.
- Water has high surface tension, high specific heat capacity, and acts as a universal solvent.
- Ice floats because frozen water is less dense due to its molecular structure.
Solutions, Acids, and Bases
- A solution is a homogeneous mixture; solvent is present in greater amount, solute dissolves.
- pH scale measures acidity or basicity based on H3O+ and OH- concentrations.
- Polar molecules have partial charges due to unequal electron sharing.
Organic Chemistry and Macromolecules
- Organic molecules have carbon backbones; inorganic molecules do not.
- Hydrocarbons contain only carbon and hydrogen; they are nonpolar and hydrophobic.
- Functional groups alter molecule reactivity and make hydrocarbons hydrophilic.
- Monomers are small building blocks; polymers are long chains of monomers.
- Dehydration synthesis joins monomers by removing water; hydrolysis splits them by adding water.
- Four main macromolecules: carbohydrates, lipids, proteins, nucleic acids.
Macromolecule Details
- Carbohydrates are sugars providing cell energy; built from monosaccharides.
- Proteins are polymers of amino acids; shape determines function.
- Lipids (fats, steroids, phospholipids) are hydrophobic; saturated fats are solid, unsaturated are liquid.
- Nucleic acids (DNA, RNA) are polymers of nucleotides.
Enzymes and Catalysis
- Enzymes are protein catalysts that lower activation energy in reactions.
- Catalysts speed up reactions without being consumed.
- Enzyme’s active site binds specific substrates for the reaction.
- Denaturation is loss of enzyme shape/function due to pH or temperature changes.
Key Terms & Definitions
- Atom — Basic unit of matter with protons, neutrons, electrons.
- Isotope — Element variant with different neutron number.
- Ionic bond — Bond from electron transfer.
- Covalent bond — Bond from electron sharing.
- Cohesion — Attraction between similar molecules.
- Enzyme — Protein that speeds up reactions.
- Denaturation — Loss of protein structure/function.
Action Items / Next Steps
- Review macromolecule types and their functions.
- Practice identifying types of bonds and properties of water.
- Complete assigned readings on enzyme activity and pH.