Course: Anatomy & Physiology I (BIOL 2301 + BIOL 2101) · Silver Oak University (fictional sample) · Prof. Navarro
Module: Week 3 of 16 · Fall 2026 · in-person, two 75-minute lectures + one weekly lab
Objective covered: Objective 2 — Describe the structure and function of the plasma membrane and the major organelles, and explain how materials cross the membrane by passive transport, active transport, and bulk transport — including osmosis and the prediction of tonicity outcomes.

This file holds two pieces: (A) the Module 3 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 3 meeting Tue Sep 15 and Thu Sep 17, a lab that same week, and end-of-week work due Sunday Sep 20, 11:59 p.m. Adjust the day-of-week and times to match your section.

(A) Module 3 Overview — Start Here

Welcome to Week 3: The Cell — and How Things Get In and Out

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 we built the body from atoms and water up to pH; this week we arrive at the cell — the smallest living unit, the rung on the organization ladder where life actually happens. We'll do two things every nurse and clinician relies on: name the cell's parts and say what each one does (the structure→function habit, applied to organelles), and explain how the cell controls what crosses its membrane — including the one piece of physiology that decides whether a red blood cell swells, shrinks, or stays the same in a given fluid. That last idea, tonicity, is why an IV bag has to be mixed exactly right, and it's this week's quantitative pocket.

The week's big question

"What is a cell made of, and how does it decide what gets in and what stays out — including which way water moves?"

By Friday you'll pair every major organelle with its job, sort transport into passive vs. active, explain osmosis, and predict — from the numbers — whether a cell placed in a solution will swell, shrink, or hold steady.

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.

• [ ] Describe the plasma membrane as a phospholipid bilayer (hydrophilic heads out, hydrophobic tails in) studded with proteins, and explain what "selectively permeable" means.
• [ ] Pair each major organelle with its function — nucleus (DNA/control), ribosome (protein synthesis), rough ER (protein processing), smooth ER (lipid synthesis, Ca²⁺ storage), Golgi (package/ship), mitochondria (ATP), lysosome (digestion), cytoskeleton (support), cilia/flagella (movement).
• [ ] Sort membrane transport into passive (no ATP, down the gradient: simple diffusion, facilitated diffusion, osmosis) vs. active (needs ATP, against the gradient: the Na⁺/K⁺ pump — 3 Na⁺ out, 2 K⁺ in) and bulk (endocytosis in, exocytosis out).
• [ ] Explain osmosis (water moves toward higher solute) and predict tonicity outcomes from osmolarity: a 300-mOsm cell swells in a 100-mOsm (hypotonic) bath, shrinks in a 500-mOsm (hypertonic) bath, and stays the same in a 300-mOsm (isotonic) bath.

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 reverse hypotonic and hypertonic (saying a cell shrinks in a hypotonic bath), mis-state the Na⁺/K⁺ pump ratio, or pair an organelle with the wrong function. 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. "Selectively permeable" just means "the cell is picky about what crosses." "Osmosis" is just "water moving to where the solute is more crowded." Picture first, term second.
• Memorize two tiny hooks. "Water follows solute — it moves toward the side with more dissolved stuff." And for tonicity: "hypO = swellO" (hypotonic → water in → the cell swells); hyper is the opposite (shrinks).
• Always compare the outside to the inside. Tonicity is never about one number alone — it's the bath vs. the cell (~300 mOsm). Lower outside → swells; higher outside → shrinks; equal → no change.
• Pair every organelle out loud. Don't memorize a list — say "mitochondria → ATP, ribosome → builds proteins, lysosome → digests." Structure→function, one organelle at a time.
• Treat the chatbot as a smart intern, not an oracle. It drafts; you check. Tonicity is exactly where chatbots flip the answer — and at the bedside, a flipped hypo/hyper is a dangerous IV.

You don't need any background beyond Weeks 1–2 — just your own curiosity about the tiny machine every part of you is built from. Come to class ready to bet on whether a cell in pure water swells or shrinks. See you Tuesday.

(B) Welcome Announcement — Module 3

Release setting: post on the module's start day (offset = 0 days), i.e., Tue Sep 15, 2026 — not before. If your platform won't preserve the scheduled date on import, post this as a draft labeled "Release: Tue Sep 15."

Subject: Welcome to Week 3 — does a red blood cell in pure water swell or shrink? 💧

Hi everyone, and welcome to Week 3!

Quick warm-up before we start: drop a red blood cell into a glass of pure water — does it swell up, shrink down, or stay the same? Hold your answer. Most people guess wrong, and the reason why is the heart of this week: water doesn't move randomly — it moves toward wherever the dissolved stuff is more crowded. The cell is packed with solutes (~300 mOsm); pure water has almost none — so water rushes in, and the cell swells (and can burst). Get that backwards in a hospital and you've mixed a dangerous IV.

This week — Cell Structure, Function & Membrane Transport — we tackle the big question: What is a cell made of, and how does it decide what gets in and out — including which way water moves? By Friday you'll name every major organelle and its job, sort transport into passive vs. active vs. bulk, explain osmosis, and predict tonicity outcomes from the numbers (this is our second quantitative pocket — keep a calculator handy, though the math stays clean).

Three things not to miss:
1. Lecture Tutorial 3 — work through the membrane, the organelles, the transport types, and tonicity with one approved chatbot (Gemini, Claude, or ChatGPT) and submit the share link. You'll catch the model's mistakes — tonicity is exactly where it flips the answer. Due Sun Sep 20.
2. Lab 3 ("Which Way Does the Water Go?"), Quiz 3, Discussion 3, and Assignment 3 also close Sun Sep 20 — the lab uses the free PhET Membrane Channels simulation, so start early and watch the particles move.
3. Open the Start Here page first — it lays out everything in order with due dates.

One promise: by Friday, the next time you see an IV bag labeled "0.9% saline," you'll know exactly why it's that number and not pure water — and you'll be able to predict what would happen to a cell if it weren't. That's structure→function and homeostasis, right down at the level of a single cell.

Bring your curiosity (and that calculator) to class on Tuesday.

See you soon,
Prof. Navarro