Week 2 — Quiz (auto-graded) · The Chemistry of Life

Course: Anatomy & Physiology I (BIOL 2301 + BIOL 2101) · Silver Oak University (fictional sample) · Prof. Navarro
Objective tested: Objective 2 — atoms & chemical bonds; properties of water; pH, acids, bases & buffers (quantitative); the four biomolecules & structure→function.
Points: 10 (1 each) · Assignment group: Quizzes (10% of grade) · Due: end of Module 2.

This is the human-readable quiz with its vetted answer key and feedback. The import-ready Classic QTI is in F-quiz-week-02-qti.xml (generated by the shared validated script — parses with 10 items, every single-answer item exactly one correct). The reusable item-bank entries and the Canvas placement block are at the bottom of this file.

Blueprint

No trick questions; distractors target the Week 2 misconceptions named in the lecture outline. Quantitative items (4 and 9) use clean integer pH differences; every fold-change is pre-computed and independently re-verified.

Questions, key, and feedback

Q1 (MC). What determines which element an atom is (for example, what makes an atom carbon rather than oxygen)?
- A. The number of protons in the nucleus ✅
- B. The number of neutrons in the nucleus
- C. The number of electron shells it has
- D. The total mass of the atom
Feedback: The number of protons is the atom's identity — 6 protons is always carbon, 8 is always oxygen. Neutrons can vary (isotopes) and electrons can be gained/lost (ions) without changing which element it is.

Q2 (MC). In an ionic bond, what happens to the electrons, and in a covalent bond, what happens to them?
- A. Ionic = electrons are shared; covalent = electrons are transferred
- B. Ionic = electrons are transferred (one atom gives, one takes); covalent = electrons are shared ✅
- C. Both ionic and covalent bonds transfer electrons completely
- D. Both ionic and covalent bonds share electrons equally
Feedback: Ionic = transfer (atoms become charged ions and attract — e.g., Na⁺ and Cl⁻ in table salt). Covalent = share (and the sharing can be equal/nonpolar or unequal/polar). A reverses the two; C and D collapse the distinction.

Q3 (Multiple answer — select all that apply). Which of the following are true properties of water that come from its polarity?
- A. Water shows cohesion (its molecules stick to one another, creating surface tension) ✅
- B. Water is a good solvent (the universal solvent) and dissolves salts and other polar molecules ✅
- C. Water has a high heat capacity, so it resists temperature change and buffers body temperature ✅
- D. Water is a nonpolar molecule
- E. Water cannot dissolve salts such as sodium chloride
Feedback: Water's cohesion, solvent power, and high heat capacity all flow from its polarity (a slightly negative oxygen end, slightly positive hydrogen ends). D is false — water is polar — and E is false — water dissolves salts precisely because it's polar. Those two are the distractors.

Q4 (MC). Each whole step on the pH scale is a 10× change in hydrogen-ion (H⁺) concentration. A solution at pH 4 compared with a solution at pH 7 is how many times more acidic?
- A. 3 times more acidic
- B. 30 times more acidic
- C. 300 times more acidic
- D. 1000 times more acidic ✅
Feedback: Count the units (7 − 4 = 3), then multiply by 10 for each (10 × 10 × 10 = 1000 = 10³). So pH 4 has 1000× more H⁺ than pH 7 — 1000× more acidic. "3 times" (A) is the classic error of subtracting instead of multiplying by 10 per unit.

Q5 (MC). A solution with a pH of 9 is best described as:
- A. Basic, with FEWER hydrogen ions (H⁺) than pure water at pH 7 ✅
- B. Acidic, with MORE hydrogen ions (H⁺) than pure water at pH 7
- C. Neutral, with exactly the same H⁺ as pure water
- D. Basic, but with MORE hydrogen ions than pure water
Feedback: Higher pH = fewer H⁺ = more basic (alkaline). pH 9 is above neutral (7), so it has fewer H⁺ than pure water and is basic. B and D get the H⁺ direction backwards; the rule is more H⁺ → lower pH.

Q6 (Matching). Match each biomolecule (large molecule) to its building block (monomer or basic unit).
| Biomolecule | Correct building block |
|---|---|
| Carbohydrate | Monosaccharide (simple sugar) |
| Protein | Amino acid |
| Nucleic acid (DNA/RNA) | Nucleotide |
| Lipid (fat) | Fatty acids and glycerol (no single repeating monomer) |
Feedback: Carbs are chains of monosaccharides; proteins are chains of amino acids; nucleic acids are chains of nucleotides. Lipids are the exception — they have no single repeating monomer; a fat is built from fatty acids + glycerol. Pairing lipid with "fatty acids + glycerol" is the catch.

Q7 (MC). What does a buffer (such as the bicarbonate buffer system in blood) do?
- A. It resists changes in pH by absorbing extra H⁺ or releasing H⁺ as needed ✅
- B. It permanently raises the pH of the blood to 14
- C. It speeds up every chemical reaction in the cell
- D. It stores genetic information for the cell
Feedback: A buffer resists pH change — soaking up extra H⁺ when acid rises and releasing H⁺ when it falls — which is how blood holds near pH 7.4. (B is impossible; C describes enzymes; D describes nucleic acids.)

Q8 (True / False). "The pH of human blood is normally about 2."
- True
- False ✅
Feedback: False. Blood pH is tightly regulated at about 7.35–7.45 (~7.4) — slightly basic. pH 2 is roughly stomach acid. A blood pH anywhere near 2 is incompatible with life.

Q9 (MC). Because each whole pH unit equals a 10× change in H⁺, a difference of 2 whole pH units (for example, pH 6 vs pH 8) means a difference of how many times in H⁺ concentration?
- A. 2 times
- B. 20 times
- C. 100 times ✅
- D. 200 times
Feedback: 2 units → 10 × 10 = 100× (10²). The classic wrong answers come from adding (B, "20×") or subtracting (A, "2×"). Always: count the whole units, then raise 10 to that power. (And pH 8 is the more basic of the two — fewer H⁺.)

Q10 (MC). Why can a change in a protein's three-dimensional shape stop the protein from working (for example, an enzyme that no longer fits its target)?
- A. Because a protein's function depends on its shape/structure (structure determines function) ✅
- B. Because proteins are made of nucleotides, which carry the genetic code
- C. Because proteins store all of the cell's long-term energy
- D. Because a protein's shape has nothing to do with what it does
Feedback: A protein's job — gripping a target, forming a channel, building a fiber — depends on its folded shape. Change the shape and you change (or break) the function: structure determines function, right down at the molecule. (B confuses proteins with nucleic acids; C confuses them with carbs/lipids; D is the opposite of the truth.)

Answer key (quick reference)

Quality gate (self-checked): each single-answer item has exactly one correct option; the multiple-answer item (Q3) requires the three true properties (A, B, C) selected and the two distractors (D "nonpolar", E "cannot dissolve salts") left unselected; the matching item pairs four biomolecules to four distinct building blocks. Every chemistry fact is verified against standard references (OpenStax A&P §2.1–2.5). Anatomy/chemistry-accuracy gate: PASS. The two quantitative items were pre-computed and independently re-verified in Python (each pH unit = 10×; pH 4 vs 7 = 3 units = 10³ = 1000×; pH 6 vs 8 = 2 units = 10² = 100×); the answer keys (Q4 = D/1000×, Q9 = C/100×) match the verified values. Quantitative gate: PASS.

Item-bank entries (for variants + the midterm/final)

All ten items are tagged course=BIOL2301 · week=2 · objective=2 · topic=chemistry-of-life and deposited in Item Bank: Week 2 — Chemistry of Life (atoms, bonds, water, pH, biomolecules). The midterm (Week 8) and the per-term variant updates draw fresh items from this bank — including the pH quantitative items, which the midterm reuses to satisfy its quantitative requirement. (Tags: q1 atom-protons, q2 ionic-vs-covalent, q3 water-properties, q4 ph-fold-1000x, q5 ph9-basic, q6 biomolecule-monomer-match, q7 buffer-function, q8 blood-ph-misconception, q9 ph-unit-10x, q10 protein-structure-function.)

Canvas placement block

canvas_object   = Quizzes::Quiz
title           = "Week 2 Quiz — The Chemistry of Life"
assignment_group = "Quizzes"
points_possible = 10
grading_type    = points
due_offset_days = 5        # 5 days after module start (Tue Sep 8 -> Sun Sep 13)
published       = true
shuffle_answers = true
provenance      = "~ Prof. Navarro's edition · Fall 2026 · built with thecoursemaker.com"