Study Guide Module 2: Small Molecules & Chemistry of Life - Organized

Here's the study guide information organized for easier memorization, using headings, bullet points, and summaries:

I. Overview: Chemical Connection to Biology

• Living organisms obey physics & chemistry laws.

• Biology is multidisciplinary.

• Life has a structural hierarchy: Atoms → Molecules → Cells → ... Emergent properties appear at each level.

• The transition from nonlife to life occurs between molecules and cells.

II. Concept 2.1: Matter & Elements

• Matter: Anything with mass and volume. Composed of elements.

• Element: Substance that can't be broken down chemically. 92 natural elements, each with a unique symbol.

• Compound: Two or more elements in a fixed ratio (e.g., NaCl). Emergent properties arise (Na/Cl → edible salt).

• Essential Elements: 20-25 needed for life. Humans: 25, Plants: 17.

  • Major Elements (96% of living matter): O, C, H, N

  • Remaining 4%: Ca, P, K, S

  • Trace Elements: Required in small amounts (e.g., Fe, I). Some are species-specific.

• Toxic Elements: Some natural elements are toxic (e.g., arsenic). Some organisms adapt.

III. Concept 2.2: Atomic Structure & Properties

• Atom: Smallest unit retaining element properties.

• Subatomic Particles:

  • Nucleus: Protons (+) and Neutrons (neutral)

  • Electron Cloud: Electrons (-)

• Dalton: Unit for atomic mass (proton/neutron ≈ 1 dalton, electron ≈ 1/2000 dalton).

• Atomic Number: Number of protons (subscript before symbol, e.g., ₂He). Also equals number of electrons in a neutral atom.

• Mass Number: Protons + Neutrons (superscript before symbol, e.g., ⁴He). Approximates atomic mass.

• Isotopes: Atoms of the same element with different neutron numbers (e.g., ¹²C, ¹³C, ¹⁴C).

  • Stable Isotopes: Don't decay.

  • Radioactive Isotopes: Unstable, decay spontaneously, emitting particles & energy (e.g., ¹⁴C). Used in dating, tracing, and medicine (PET scans), but hazardous.

• Electron Configuration: Influences chemical behavior.

  • Electrons have potential energy based on distance from nucleus.

  • Electron Shells (energy levels): 1st shell (max 2e⁻), 2nd shell (max 8e⁻), etc.

  • Valence Shell: Outermost shell. Valence Electrons: Electrons in valence shell. Determine chemical reactivity.

  • Inert Atoms: Complete valence shell (e.g., Ne).

  • Orbitals: 3D space where electrons are found 90% of the time (s and p orbitals). Max 2e⁻ per orbital. Unpaired electrons are reactive.

IV. Concept 2.3: Chemical Bonding

• Chemical Bonds: Attractions between atoms due to shared or transferred valence electrons.

• Covalent Bond: Sharing of valence electrons.

  • Molecule: Two or more atoms held by covalent bonds.

  • Molecular Formula (e.g., H₂). Structural Formula (e.g., H-H). Lewis Dot Structure (e.g., H:H).

  • Single, Double, Triple Bonds: Sharing 1, 2, or 3 pairs of electrons.

  • Valence: Bonding capacity (H=1, O=2, N=3, C=4, P=5).

  • Nonpolar Covalent Bond: Equal sharing (same element or similar electronegativity).

  • Polar Covalent Bond: Unequal sharing (different electronegativity). Partial charges (δ⁻, δ⁺).

• Electronegativity: Atom's attraction for shared electrons.

• Ionic Bond: Electron transfer. Forms ions (charged atoms).

  • Cation: Positive ion (e.g., Na⁺). Anion: Negative ion (e.g., Cl⁻).

  • Ionic Compound (Salt): Lattice of cations and anions (e.g., NaCl).

• Weak Chemical Bonds: Important in biological systems. Reversible.

  • Hydrogen Bonds: H bonded to an electronegative atom (O or N) attracted to another electronegative atom.

  • Van der Waals Interactions: Temporary, fluctuating partial charges due to electron movement.

V. Molecule Shape & Function

• Shape is crucial for biological function.

• Determined by electron orbitals.

• Hybridization: Mixing of orbitals (e.g., tetrahedral shape of carbon).

• Molecular Recognition: Specific interactions based on shape (e.g., drug binding to receptors).

VI. Concept 2.4: Chemical Reactions

• Chemical Reaction: Breaking and forming bonds.

• Reactants: Starting molecules.

• Products: Final molecules.

• Balanced Equation: Atoms are conserved (same number on both sides).

• Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (powered by sunlight).

• Reversible Reactions: Can proceed forward or backward.

• Chemical Equilibrium: Forward and reverse rates are equal. Concentrations of reactants and products are stable (not necessarily equal).

• Reactions that go to completion: All reactants are converted to products.

This structure should make it easier to review and remember the key concepts and details of Module 2. Remember to use diagrams and examples to further solidify your understanding. Good luck!