Safety and evidence boundary
This week uses fictional signaling systems, published-style graphs, and card or digital models. It does not diagnose hormone, neurological, immune, or other medical conditions and does not require personal health information.
Explicit science instruction
Models allow students to manipulate signaling components without using living tissue or medical data. A useful signaling model has explicit rules: what activates each component, what each component activates next, what counts as the response, and what assumptions are being made.
Changing one component can generate predictions. Removing the receptor should block a receptor-dependent pathway. Removing a downstream component may block only one branch. A component that is modeled as permanently active could produce response without the usual upstream signal.
The value of the model comes from comparing predictions to evidence and identifying its limitations. A model that produces any desired outcome after rules are changed without justification has little explanatory power.
Vocabulary: perturbation; knockout model; constitutive activation; pathway branch; prediction; model rule; control condition.
Worked example with reasoning
Fictional pathway: Ligand → Receptor R → A → B → response. Control cells show response only when ligand is present. A model with inactive R predicts no response with or without ligand. A model with permanently active B predicts response even without ligand. These contrasting predictions can help locate where a perturbation acts in the pathway.
Guided question
If ligand is present and receptor R activates normally, but no response occurs, which downstream components would you inspect next and why?
Independent work
- Build the baseline pathway model.
- Test at least three perturbations.
- Record predicted outcomes in a table.
- Identify one control condition.
- Write one limitation of the card-model rules.
Misconception check
A pathway diagram is not proof that molecules literally line up in that order inside a cell. It is a causal abstraction. Physical location, timing, concentrations, competing pathways, and molecular interactions may be much more complex.
Formative understanding check
Why is a no-signal control useful in the pathway model?
Show the worked response
It establishes the baseline response when the ligand is absent, helping distinguish signal-dependent activity from background or constitutive pathway activity.
Open-book formative practice only; not an official mastery attempt or grade.
Mentor evidence conference
Ask Archaemenes to identify where your model skips a step between signal, receptor, intracellular transduction, and response. The mentor may challenge reasoning but does not provide protected assessment answers.
Open Archaemenes for this lessonTeacher guidance
Foundation: use a fixed four-step pathway and two perturbations. Core: require predictions and controls. Extended: add branching and feedback, then ask which additional observation would discriminate among competing models.
Preserve learning evidence
Keep the signaling model, graph or data interpretation, correction note, and explanation in the matching Week 13 evidence field.
Return to thursday Evidence Workspace