AP Biology · Unit 4
Cell Communication and Cell Cycle
Follow biological information from a signal to a cellular response, then examine how signaling and checkpoints coordinate cell division.
Learning sequence
Choose a lesson
Topic 4.1
How Cells Send Messages
Compare contact, local, synaptic, endocrine, and pheromone signaling.
Topic 4.2
Reception → Transduction → Response
Connect ligand properties, receptor location, cascades, second messengers, and amplification.
Topic 4.3
Pathways, Responses & Mutations
Predict how mutations, agonists, antagonists, and pathway position alter responses.
Topic 4.4
Feedback and Homeostasis
Build negative and positive feedback loops and interpret set-point data.
Topic 4.5
The Cell Cycle and Mitosis
Sequence chromosome events, track DNA content, and analyze microscopy counts.
Topic 4.6
Checkpoints, Cyclins & Cancer
Connect regulatory signals and mutations to arrest, apoptosis, or uncontrolled division.
Topics 4.1–4.6
Unit 4 Assessment
Analyze signaling models, feedback data, cell-cycle evidence, and regulatory disruptions.