Week 7 — Quiz (auto-graded) · Photosynthesis

Course: Introduction to Biology — General Biology I (BIOL 101) · Silver Oak University (fictional sample) · Prof. Castellano
Objective tested: Objective 4 — the photosynthesis equation; chloroplast structure; the two stages' order, location, inputs, and outputs; where O₂ comes from; the Calvin cycle's dependence on the light reactions; photosynthesis vs. respiration.
Points: 10 (1 each) · Assignment group: Quizzes (10% of grade) · Due: end of Module 7.

This is the human-readable quiz with its vetted answer key and feedback. The import-ready Classic QTI is in F-quiz-week-07-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 7 misconceptions named in the lecture outline (O₂-from-CO₂, stages out of order, Calvin-cycle-in-the-dark, mass-from-soil, thylakoid/stroma mix-up).

Questions, key, and feedback

Q1 (MC). In the photosynthesis equation, 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂, which pair lists the products (what photosynthesis makes)?
- A. carbon dioxide and water
- B. glucose and oxygen ✅
- C. light energy and water
- D. carbon dioxide and oxygen
Feedback: The products are on the right of the arrow: glucose (C₆H₁₂O₆) and oxygen. The reactants (inputs) are CO₂, water, and light energy. (D mixes a reactant with a product.)

Q2 (MC). A plant releases oxygen during photosynthesis. Where do those oxygen atoms actually come from?
- A. from the carbon dioxide (CO₂)
- B. from the glucose the plant builds
- C. from splitting water (H₂O) in the light reactions ✅
- D. from the soil around the roots
Feedback: The O₂ comes from splitting water during the light-dependent reactions — not from CO₂. Follow the atoms: O₂ ← H₂O. (The carbon and oxygen in CO₂ end up in sugar, in the Calvin cycle.)

Q3 (Multiple answer — select all that apply). Which of the following are true of the light-dependent reactions?
- A. They take place in the thylakoid membrane ✅
- B. They split water and release O₂ ✅
- C. They produce ATP and NADPH ✅
- D. They fix CO₂ into sugar
- E. They take place in the stroma
Feedback: The light reactions happen in the thylakoid membrane (A), split water → release O₂ (B), and make ATP and NADPH (C). Fixing CO₂ into sugar (D) and the stroma (E) belong to the Calvin cycle, the other stage.

Q4 (MC). The Calvin cycle (the light-independent reactions) takes place in which part of the chloroplast?
- A. the thylakoid membrane
- B. the stroma ✅
- C. the outer membrane
- D. the mitochondrion
Feedback: The Calvin cycle runs in the stroma, the fluid surrounding the thylakoids. (The light reactions run in the thylakoid membrane; the mitochondrion is where respiration happens, not photosynthesis.)

Q5 (MC). Which stage of photosynthesis happens first, and why?
- A. The light-dependent reactions — they capture light energy as ATP and NADPH, which the next stage needs ✅
- B. The Calvin cycle — it makes the sugar that powers the light reactions
- C. They happen in either order; it doesn't matter
- D. The Calvin cycle — it splits water to release oxygen
Feedback: The light reactions come first: they capture energy as ATP and NADPH, and the Calvin cycle then spends that energy to build sugar. Energy must be captured before it can be spent. (Water-splitting is a light-reaction job, not a Calvin-cycle job — eliminating D.)

Q6 (Matching). Match each stage or structure to the correct description.
| Item | Correct description |
|---|---|
| Light-dependent reactions | Happen in the thylakoid membrane; split water and make ATP + NADPH |
| Calvin cycle | Happens in the stroma; fixes CO₂ into sugar using ATP + NADPH |
| Oxygen (O₂) | A product released when water is split |
| Glucose | The sugar product where the carbon from CO₂ ends up |
Feedback: The light reactions (thylakoid) split water and make ATP + NADPH; the Calvin cycle (stroma) uses those to fix CO₂ into sugar. O₂ comes from splitting water; glucose is where the CO₂ carbon ends up. This is the whole week in one grid: order, location, inputs, outputs.

Q7 (MC). A student says, "The Calvin cycle is the 'light-independent' stage, so it works just fine in the dark." What is the correct response?
- A. Correct — it never needs light or anything from the light reactions
- B. Wrong — the Calvin cycle uses light directly, just like the light reactions
- C. Wrong — it doesn't use light directly, but it depends on the ATP and NADPH the light reactions make, so it stops without light ✅
- D. Wrong — the Calvin cycle happens in the mitochondria, not the chloroplast
Feedback: "Light-independent" means the Calvin cycle doesn't use photons directly — but it completely depends on the ATP and NADPH supplied by the light reactions. In the dark, those run out and the cycle stops within minutes. (It does not use light directly (B is wrong), and it runs in the stroma of the chloroplast (D is wrong).)

Q8 (True / False). "Plants carry out photosynthesis instead of cellular respiration; only animals do respiration."
- True
- False ✅
Feedback: False. Plants do both. Photosynthesis (in chloroplasts) builds sugar in the light; cellular respiration (in mitochondria) breaks sugar down to make ATP, day and night. Making food and burning food are two different jobs.

Q9 (MC). How do photosynthesis and cellular respiration relate to each other?
- A. They are identical processes with different names
- B. They are roughly reverse processes — the products of one are the inputs of the other ✅
- C. They both release oxygen as a product
- D. Photosynthesis makes ATP directly for the whole body to use
Feedback: They're roughly reverse: photosynthesis turns CO₂ + H₂O + light into glucose + O₂, while respiration turns glucose + O₂ into CO₂ + H₂O + ATP. The by-products of one are the raw materials of the other. (Respiration consumes O₂; photosynthesis stores energy in sugar, which respiration later converts to ATP.)

Q10 (MC). A giant tree gains hundreds of kilograms of mass as it grows, yet the soil in its pot loses almost no mass. Where does most of that added mass come from?
- A. from minerals pulled out of the soil
- B. from the water alone
- C. from carbon dioxide (CO₂) in the air, fixed into sugar by photosynthesis ✅
- D. from sunlight being converted directly into matter
Feedback: Most of a plant's dry mass is carbon, and that carbon comes from CO₂ in the air, fixed into sugar during the Calvin cycle — "a tree is mostly built from thin air." Soil supplies water and minerals, not the bulk of the mass; and energy (sunlight) is not converted into matter (D).

Answer key (quick reference)

Quality gate (self-checked): each single-answer item has exactly one correct option; the multiple-answer item lists all three true light-reaction facts (A, B, C) and requires D and E (which describe the Calvin cycle) to be left unselected; the matching item pairs four items to four distinct descriptions that encode the stages' order, location, inputs, and outputs. The two load-bearing misconceptions are tested head-on: O₂ comes from splitting water (Q2, Q6) and the Calvin cycle needs the light reactions' ATP/NADPH (Q7). This is a conceptual (process-order) week — there is no curriculum arithmetic in the quiz, so no numeric values to mis-key (the lab carries this week's quantitative trend check; quantitative gate for the lab: PASS, re-verified by a Python check).

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

All ten items are tagged course=BIOL101 · week=7 · objective=4 · topic=photosynthesis and deposited in Item Bank: Week 7 — Photosynthesis. The midterm (Week 8) and the per-term variant updates draw fresh items from this bank. (Tags: q1 equation-products, q2 oxygen-from-water, q3 light-reactions-facts, q4 calvin-stroma, q5 stage-order, q6 stage-location-io-match, q7 light-independent-misconception, q8 plants-also-respire, q9 photo-vs-respiration, q10 mass-from-air.)

Canvas placement block

canvas_object   = Quizzes::Quiz
title           = "Week 7 Quiz — Photosynthesis"
assignment_group = "Quizzes"
points_possible = 10
grading_type    = points
due_offset_days = 5        # 5 days after module start (Sun Oct 18)
published       = true
shuffle_answers = true
provenance      = "~ Prof. Castellano's edition · Fall 2026 · built with thecoursemaker.com"