Course: Introduction to Biology — General Biology I (BIOL 101) · Silver Oak University (fictional sample) · Prof. Castellano
Module: Week 7 of 16 · Fall 2026 · in-person, two 75-minute lectures + one weekly lab
Objective covered: Objective 4 — Trace how cells capture, store, and release energy — and explain photosynthesis as an ordered, two-stage process (light reactions → Calvin cycle) that stores light energy in sugar.

This file holds two pieces: (A) the Module 7 Overview page ("Start Here") and (B) the Welcome Announcement that drips out when the module opens. Dates below assume a Tuesday/Thursday lecture pattern with Week 7 meeting Tue Oct 13 and Thu Oct 15, a lab that same week, and end-of-week work due Sunday Oct 18, 11:59 p.m. Adjust the day-of-week and times to match your section.

(A) Module 7 Overview — Start Here

Welcome to Week 7: Photosynthesis

This is your home base for the week. Read it first, then work the checklist below from top to bottom. Everything you need is linked inside the module.

Last week you learned how cells spend energy — they break sugar down in cellular respiration to make ATP. This week we flip the arrow and ask the opposite question: where does that sugar come from in the first place? The answer is photosynthesis, the process by which plants, algae, and some bacteria capture energy from sunlight and store it in the bonds of sugar. It is, quite literally, how energy from the sun gets into the food chain — every bite you eat traces back to it. Two ideas carry the week: photosynthesis happens in two ordered stages, and the famous equation runs roughly in reverse of respiration.

The week's big question

"How does a plant turn sunlight, air, and water into food — and where does the oxygen you're breathing come from?"

By Friday you'll be able to write the photosynthesis equation, locate and order its two stages inside the chloroplast, say exactly what each stage takes in and puts out, and explain why a tree's mass comes mostly from thin air rather than from the soil.

By the end of this week, you can…

Use this as a checklist. If you can do all four out loud, you're ready for the quiz.

• [ ] Write and read the photosynthesis equation — CO₂ + H₂O + light energy → glucose (C₆H₁₂O₆) + O₂ — and name the reactants and products.
• [ ] Locate and order the two stages in the chloroplast — the light-dependent reactions in the thylakoid membrane, then the Calvin cycle (light-independent reactions) in the stroma.
• [ ] State each stage's inputs and outputs — light reactions: split water → release O₂, make ATP + NADPH; Calvin cycle: fix CO₂ using that ATP + NADPH to build sugar (G3P → glucose).
• [ ] Connect photosynthesis to respiration (roughly reverse processes) and explain why a plant's mass comes from CO₂ in the air, not from soil.

What's due this week, and when

Work these in order — each one gets you ready for the next.

Heads-up on the AI tools: you'll use a chatbot to draft and explain, and then you judge its work against what we cover in class. Chatbots routinely put the two stages out of order, say the O₂ comes from CO₂ (it comes from splitting water), or claim the Calvin cycle "doesn't need light" (it needs the ATP and NADPH the light reactions make). Catching the model is the point — in the tutorial, the assignment, and the lab.

Late policy reminder: 10% off per day late. If life happens, reach out before the deadline — I'd much rather hear from you early.

How to succeed this week

• Lead with the idea, not the jargon. Strip it to a sentence first: light reactions catch the energy; the Calvin cycle uses that energy to build sugar. The vocabulary (thylakoid, stroma, NADPH) comes after the two-step story clicks.
• Memorize two tiny hooks. "Light reactions make the energy money (ATP + NADPH); the Calvin cycle spends it on sugar." And "The O₂ you breathe came from a split water molecule — not from CO₂."
• Practice the order out loud. Light reactions (thylakoid) come first and hand their products to the Calvin cycle (stroma) second. If you can say which comes first and where each happens, half the quiz is done.
• Remember the headline lesson: a tree is mostly built from air. The carbon in wood comes from CO₂, pulled out of the atmosphere and fixed into sugar. Soil supplies water and minerals — not the bulk of the mass.
• Treat the chatbot as a smart intern, not an oracle. It drafts; you check. That habit is the whole semester in miniature — and this week the model loves to flip where the oxygen comes from.

You don't need anything from outside class for this week — just last week's idea that cells run on ATP, and a willingness to follow energy and atoms as they move. Come to class ready to argue about where the mass of a giant redwood actually came from. See you Tuesday.

(B) Welcome Announcement — Module 7

Release setting: post on the module's start day (offset = 0 days), i.e., Tue Oct 13, 2026 — not before. If your platform won't preserve the scheduled date on import, post this as a draft labeled "Release: Tue Oct 13."

Subject: Welcome to Week 7 — where does a tree's mass come from? 🌱

Hi everyone,

Quick warm-up before we start: a giant redwood weighs hundreds of tons. Where did all that mass come from? Most people guess "the soil." But if you weighed the soil before and after a tree grew, you'd find almost none is missing. The wood is built mostly from carbon dioxide pulled out of thin air — captured by photosynthesis and locked into sugar. That puzzle is our way in this week.

This week — Photosynthesis — we tackle the big question: How does a plant turn sunlight, air, and water into food, and where does the oxygen you're breathing come from? Last week you saw cells spend energy in respiration; this week you'll see how that energy and that sugar get made in the first place — in two ordered stages inside the chloroplast.

Three things not to miss:
1. Lecture Tutorial 7 — work through the equation and the two stages (which comes first, where each happens, what each takes in and puts out) with one approved chatbot (Gemini, Claude, or ChatGPT) and submit the share link. You'll catch the model's mistakes — it loves to flip where the O₂ comes from. Due Sun Oct 18.
2. Lab 7 ("The Floating Leaf Disk"), Quiz 7, Discussion 7, and Assignment 7 also close Sun Oct 18 — in the lab you'll literally watch oxygen production lift leaf disks in the light (and stall in the dark), so start early.
3. Open the Start Here page first — it lays out everything in order with due dates.

One promise: by Friday, the next time someone says plants "eat dirt," you'll be able to set them straight — with the equation, the two stages, and the line that ties it together: the carbon in every plant came from the air, and the oxygen in every breath came from water.

Bring your curiosity (and a strong guess about that redwood) to class on Tuesday.

See you soon,
Prof. Castellano