BIOL 141: Foundations of Biology

Lecture 1: Scientific Method

  • Steps of the scientific method: observation, question, hypothesis, prediction, experiment, results, conclusion

  • Hypothesis: testable and falsifiable explanation

  • Prediction: expected outcome if hypothesis is correct; more specific than hypothesis

  • Theory: a well-supported explanation from many experiments; still not a proven fact

  • Hypothesis vs. Theory: both are explanations, but theories are broader and supported by more evidence

  • Control group: does not receive experimental variable; used for comparison

  • Experimental group: receives experimental variable

  • Independent variable: the variable manipulated by the experimenter

  • Dependent variable: the measured response/outcome

Lecture 2: Chemical Basis of Life

  • Matter: anything with mass and takes up space

  • Element: pure substance with one type of atom

  • Atom: smallest unit of an element

  • Subatomic particles:

    • Protons: + charge, in nucleus

    • Neutrons: neutral, in nucleus

    • Electrons: - charge, outside nucleus

  • Atomic number = # of protons; Mass number = protons + neutrons

  • Molecule: two or more atoms bonded together

  • Compound: molecule with different types of atoms

  • Bond types:

    • Ionic: transfer of electrons

    • Polar covalent: unequal sharing

    • Nonpolar covalent: equal sharing

    • Hydrogen bonds: weak bonds between polar molecules (partial charges)

  • Isotope: same element, different neutrons/mass

  • Ion: charged atom (cation = +, anion = -)

  • Valence electrons: outer shell electrons, determine reactivity

  • Electronegativity: atom’s pull on electrons; affects bond type

Lecture 3: Water & pH

  • Hydrogen bonding gives water unique properties:

    • High specific heat: resists temp change

    • Ice floats: solid less dense than liquid

    • Cohesion: water sticks to water; Adhesion: water sticks to other things

    • Surface tension: resistance to breaking at surface

  • Water is a universal solvent (especially for polar molecules)

  • Hydrophilic: polar/charged; Hydrophobic: nonpolar

  • Acids release H+; Bases release OH−

  • pH scale:

    • Low pH = acidic (more H+)

    • High pH = basic (more OH−)

  • Buffers: stabilize pH by absorbing or releasing H+

Lecture 4: Diversity of Carbon

  • Organic molecules contain carbon and hydrogen

  • Carbon is central due to 4 bonding sites

  • Carbon backbones vary by:

    • Length

    • Branching

    • Double bonds

    • Ring formation

  • Hydrocarbons: C & H only; hydrophobic

  • Isomers:

    • Structural (different arrangement)

    • Cis-trans (same bonds, different spatial arrangement)

    • Enantiomers (mirror images)

  • Functional groups (affect reactivity & polarity):

    • Hydroxyl (–OH)

    • Sulfhydryl (–SH)

    • Carbonyl (C=O)

    • Carboxyl (–COOH)

    • Amino (–NH2)

    • Methyl (–CH3)

    • Phosphate (–PO4)

Lecture 5: Macromolecules

  • Macromolecules = polymers made of monomers

  • Polymerization: joining monomers

  • Condensation (dehydration): forms bonds, releases water

  • Hydrolysis: breaks bonds, adds water

Carbohydrates:

  • Monomer: monosaccharide (e.g. glucose)

  • Disaccharide: two sugars (sucrose, lactose, maltose)

  • Bond: glycosidic linkage

  • Polysaccharides:

    • Starch: energy in plants

    • Glycogen: energy in animals

    • Cellulose: plant cell walls

    • Chitin: fungi cell walls & insect exoskeletons

Proteins:

  • Monomer: amino acids (20 types)

  • Bond: peptide bond (between amino and carboxyl groups)

  • Protein examples: insulin, glucagon, actin, myosin, lactase, collagen, hemoglobin

  • Levels of structure:

    • Primary: amino acid sequence

    • Secondary: alpha-helix & beta-sheet (H-bonds)