Chapter 2: The Chemical Foundation of Life Flashcards
Define atom and list its subatomic particles.
The smallest unit of matter retaining an element’s properties. Subatomic particles: protons (+), neutrons (neutral), electrons (-).
What is the difference between atomic number and mass number?
Atomic number: Number of protons (e.g., carbon = 6). Mass number: Protons + neutrons (e.g., carbon-12 = 6p + 6n).
Define isotopes. Give an example.
Atoms of the same element with different neutron numbers. Example: Carbon-12 (6n) vs. Carbon-14 (8n).
What are ions? Distinguish cations and anions.
Charged atoms. Cations: Lose electrons → positive (e.g., Na⁺). Anions: Gain electrons → negative (e.g., Cl⁻).
Compare ionic bonds and covalent bonds.
Ionic: Electron transfer (e.g., NaCl). Covalent: Electron sharing (e.g., H₂O).
What is a polar covalent bond? Example.
Unequal electron sharing due to electronegativity differences. Example: H₂O (O attracts electrons more than H).
Define hydrogen bond. Why is it important in water?
Weak attraction between δ+ H and δ- O/N. Creates water’s cohesion, high heat capacity, and surface tension.
List 4 unique properties of water and their biological significance.
Cohesion (water sticks to itself → capillary action). Adhesion (water sticks to other substances → plant water uptake). High specific heat (stabilizes temperatures). Universal solvent (dissolves polar molecules).
What is a hydration shell? Example.
Layer of water molecules around dissolved ions. Example: Na⁺ and Cl⁻ in saltwater.
Explain the pH scale. What does pH = 7 mean?
Measures H⁺ concentration. pH 7 = neutral (pure water). pH <7 = acidic; pH >7 = basic.
Define acid and base with biological examples.
Acid: Releases H⁺ (e.g., stomach HCl). Base: Accepts H⁺ or releases OH⁻ (e.g., blood bicarbonate).
What is a buffer? How does it work?
Resists pH changes by absorbing/releasing H⁺. Example: Bicarbonate buffer in blood: HCO₃⁻ + H⁺ ↔ H₂CO₃.
Why is carbon the backbone of organic molecules?
Forms 4 covalent bonds, allowing diverse structures (chains, rings, branches).
What are hydrocarbons? Provide examples.
Molecules with only C and H. Examples: Methane (CH₄), propane (C₃H₈).
Define structural isomers vs. geometric isomers.
Structural: Different covalent arrangements (e.g., butane vs. isobutane). Geometric: Same bonds, different spatial arrangements (e.g., cis vs. trans fats).
What are enantiomers? Biological example.
Mirror-image molecules. Example: L-amino acids (used in proteins) vs. D-amino acids (rare).
List 6 functional groups in organic chemistry.
Hydroxyl (-OH), Carbonyl (C=O), Carboxyl (-COOH), Amino (-NH₂), Phosphate (-PO₄), Sulfhydryl (-SH).
What is the Bohr model of electron shells?
Electrons orbit the nucleus in energy levels (K, L, M shells). Example: Carbon has 2 electrons in K, 4 in L.
Why is water a polar molecule? Draw its structure.
Oxygen’s electronegativity creates δ- charge on O and δ+ on H. Bent structure with 104.5° bond angle.
What is surface tension? How does water exhibit it?
Resistance of a liquid to rupture due to hydrogen bonding. Example: Water striders walking on water.
Explain van der Waals interactions. Example.
Weak attractions between transient dipoles. Example: Gecko feet adhering to surfaces.
What is capillary action? How does it occur?
Water rising in narrow tubes due to cohesion and adhesion. Example: Water moving up plant xylem.
Define hydrophilic and hydrophobic. Examples.
Hydrophilic: Water-loving (e.g., salt). Hydrophobic: Water-fearing (e.g., oil).
What is heat of vaporization? Why is it high in water?
Energy needed to turn liquid → gas. High in water due to hydrogen bonds (requires breaking).
Describe the structure of ice. Why does it float?
Hydrogen bonds form a hexagonal lattice, making ice less dense than liquid water.
What is chemical equilibrium? Example.
Forward and reverse reaction rates are equal. Example: CO₂ + H₂O ↔ H₂CO₃ in blood.
How do radioactive isotopes differ from stable ones? Uses?
Unstable nuclei decay, emitting radiation. Uses: Carbon-14 dating, medical imaging.
What is electronegativity? Trend in the periodic table.
Atom’s ability to attract electrons. Increases across periods (left → right), decreases down groups.
Define molecule vs. compound. Examples.
Molecule: Two+ atoms bonded (e.g., O₂). Compound: Two+ elements bonded (e.g., H₂O).
What role do lipids play in cell membranes?
Phospholipids form bilayers (hydrophilic heads, hydrophobic tails). Example: Cell membrane structure.
