Week 5 — Quiz (auto-graded) · Energy, Enzymes & Metabolism

Course: Introduction to Biology — General Biology I (BIOL 101) · Silver Oak University (fictional sample) · Prof. Castellano
Objective tested: Objective 4 — energy & the two laws of thermodynamics; ATP as the cell's energy currency; enzymes & activation energy; temperature/pH effects & denaturation.
Points: 10 (1 each) · Assignment group: Quizzes (10% of grade) · Due: end of Module 5.

This is the human-readable quiz with its vetted answer key and feedback. The import-ready Classic QTI is in F-quiz-week-05-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 5 misconceptions named in the lecture outline.

Questions, key, and feedback

Q1 (MC). Which statement best reflects the first law of thermodynamics as it applies to a cell?
- A. A cell creates brand-new energy out of nothing when it needs it
- B. A cell captures and transforms energy but cannot create or destroy it ✅
- C. Energy inside a cell never changes from one form to another
- D. A cell destroys energy permanently each time it does work
Feedback: The first law says energy is conserved — it can only be transformed, never created or destroyed. A cell captures energy (from food or sunlight) and transforms it; it never makes energy from nothing (A) and energy does change form (C).

Q2 (MC). Glucose and fat store energy, but a cell cannot spend them directly for work. Which molecule is the cell's main energy currency that it spends directly to power tasks like muscle contraction?
- A. DNA
- B. ATP ✅
- C. a phospholipid
- D. cellulose
Feedback: ATP is the cell's spendable "small change." Glucose and fat are stored fuel (the big bills) that get converted into ATP. (DNA is genetic instructions — a classic distractor; a phospholipid builds membranes; cellulose is structural.)

Q3 (MC). When a cell spends energy, ATP loses one phosphate group and releases energy. What molecule does ATP become?
- A. DNA
- B. glucose
- C. ADP ✅
- D. RNA
Feedback: Spending ATP releases a phosphate and energy, leaving ADP (adenosine diphosphate — the "spent battery"). Food then recharges ADP back to ATP. "ATP is charged; ADP is spent."

Q4 (MC). What does an enzyme do to a chemical reaction in a cell?
- A. It adds extra energy to the products so they end up higher in energy
- B. It lowers the activation energy, so the reaction proceeds faster ✅
- C. It is consumed in the reaction and must be replaced each time
- D. It changes how much energy the reaction releases overall
Feedback: An enzyme lowers the activation energy — the "energy hill" — so a reaction goes faster. It does not change the start or end energy (so not A or D), and it is a reusable catalyst, not consumed (not C). "An enzyme lowers the hill, not the destination."

Q5 (Multiple answer — select all that apply). Which of the following are TRUE of enzymes?
- A. They are reusable and not used up by the reaction ✅
- B. Each enzyme is specific to a particular substrate that fits its active site ✅
- C. They lower the activation energy of a reaction ✅
- D. They permanently raise the temperature of the cell to speed reactions
- E. They are made of DNA
Feedback: Enzymes are reusable catalysts (A), specific to a substrate via the active site (B), and they work by lowering activation energy (C). They do not heat the cell (D), and they are proteins, not DNA (E).

Q6 (Matching). Match each enzyme-related term to its meaning.
| Term | Correct meaning |
|---|---|
| Substrate | The specific reactant an enzyme acts on |
| Active site | The shaped pocket on the enzyme where the substrate binds |
| Activation energy | The energy barrier a reaction must overcome to proceed |
| Denaturation | Loss of an enzyme's shape so it can no longer function |
Feedback: The substrate is the reactant; it binds the enzyme's active site; the reaction still must clear the activation-energy barrier (which the enzyme lowers); and denaturation is the loss of shape (e.g., from too much heat) that stops the enzyme working.

Q7 (MC). A human enzyme is tested at 5 °C, 22 °C, 37 °C, and after boiling at 100 °C. At which temperature is its reaction rate the fastest?
- A. 5 °C
- B. 22 °C
- C. 37 °C ✅
- D. 100 °C (boiled)
Feedback: Enzyme rate rises to an optimum — about 37 °C (body temperature) for human enzymes — then falls. Cold (5 °C, 22 °C) is slower; boiling (100 °C) denatures the enzyme, dropping the rate to ~0.

Q8 (MC). In that same experiment, the enzyme's rate after boiling at 100 °C is essentially zero. The best explanation is that the enzyme has —
- A. run out of substrate to act on
- B. been denatured, destroying the shape of its active site ✅
- C. turned into ATP
- D. simply slowed down and will speed back up if kept hot
Feedback: Boiling denatures the enzyme — the protein unfolds and the active site is destroyed, so it can't bind substrate and the rate goes to ~0. This is permanent (not D): "a boiled enzyme is a cooked egg — it doesn't un-cook."

Q9 (True / False). "For an enzyme, increasing the temperature always increases the reaction rate, no matter how high the temperature goes."
- True
- False ✅
Feedback: False. Rate increases only up to the optimum (~37 °C for human enzymes). Past it, the enzyme denatures and the rate crashes to zero. More heat is not a throttle you can keep pushing.

Q10 (MC). Breaking a large molecule down into smaller ones and releasing energy in the process is best described as a —
- A. catabolic, energy-releasing (exergonic) reaction ✅
- B. anabolic, energy-requiring (endergonic) reaction
- C. reaction that creates new energy from nothing
- D. reaction that only occurs in DNA
Feedback: Catabolic reactions break down molecules and release energy (exergonic). Anabolic reactions build molecules and require energy (endergonic) — the opposite (B). No reaction creates energy from nothing (C, first law).

Answer key (quick reference)

Quality gate (self-checked): each single-answer item has exactly one correct option; the multiple-answer item (Q5) lists the three true properties (A, B, C) and requires D and E to be left unselected; the matching item pairs four terms to four distinct meanings; no item asserts a fact outside the Week 5 course definitions. Week 5 is a conceptual week, so the quiz contains no curriculum arithmetic to mis-key; the only numbers (5/22/37/100 °C in Q7–Q8) come straight from the lab's pre-computed model trend (rate rises to a ~37 °C optimum; boiled/denatured = 0), which was independently re-derived by a Python check — quantitative gate: PASS (see the Lab's quality-gate line).

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

All ten items are tagged course=BIOL101 · week=5 · objective=4 · topic=energy-enzymes-metabolism and deposited in Item Bank: Week 5 — Energy, Enzymes & Metabolism. The final (Week 16) and the per-term variant updates draw fresh items from this bank. (Tags: q1 first-law, q2 atp-currency, q3 atp-to-adp, q4 enzyme-activation-energy, q5 enzyme-properties, q6 enzyme-terms-match, q7 temperature-optimum, q8 denaturation, q9 hotter-not-always-faster, q10 catabolic-exergonic.)

Canvas placement block

canvas_object   = Quizzes::Quiz
title           = "Week 5 Quiz — Energy, Enzymes & Metabolism"
assignment_group = "Quizzes"
points_possible = 10
grading_type    = points
due_offset_days = 6        # 6 days after module start
published       = true
shuffle_answers = true
provenance      = "~ Prof. Castellano's edition · Fall 2026 · built with thecoursemaker.com"