a ligand binds its receptor
📡AP BIOLOGY STUDY GUIDE
Unit 4: Cell Communication and Cell Cycle
Review receptors, signal transduction, feedback, mitosis, and cell-cycle control for AP Biology Unit 4.
8 key ideas8 flashcards5 practice questions
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One message can become a large response.
relay molecules pass and amplify the message
cell activity or gene expression shifts
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
Cells send signals through direct contact, local regulators, or hormones.
- 02
Reception begins when a signaling molecule binds its matching receptor.
- 03
Transduction relays a message, often through phosphorylation or second messengers.
- 04
A signaling cascade can amplify a small starting signal into a large response.
- 05
Negative feedback returns a regulated condition toward its set point.
- 06
Cyclins and cyclin-dependent kinases regulate passage through cell-cycle checkpoints.
- 07
Mitosis distributes duplicated chromosomes into two nuclei.
- 08
Apoptosis removes damaged or unneeded cells by programmed cell death.
PART OF THE AP BIOLOGY GUIDE
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Open the full AP Biology guide →Two ideas worth correcting now
NOT QUITE
→Every cell responds to every hormone
USE THIS INSTEAD
A cell must have the matching receptor and the needed relay machinery to respond.
NOT QUITE
→Interphase is a resting stage
USE THIS INSTEAD
Cells grow, copy DNA, and perform normal work during interphase.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1What are the three broad stages of cell signaling?Show answer ＋
Reception, transduction, and response.
2What does a ligand do?Show answer ＋
It binds to a receptor with a compatible binding site.
3What can a second messenger do?Show answer ＋
It relays a signal inside the cell and may amplify it.
4What happens at a cell-cycle checkpoint?Show answer ＋
Regulatory proteins determine whether the cell proceeds, pauses, or stops.
5When does DNA replication occur?Show answer ＋
During the S phase of interphase.
6What separates during anaphase of mitosis?Show answer ＋
Sister chromatids.
7What is apoptosis?Show answer ＋
Programmed cell death.
8How can a receptor mutation alter signaling?Show answer ＋
It can prevent a signal, trigger a response without a ligand, or modify signal strength.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01How can one signaling molecule produce a large cellular response?
Each activated molecule can activate several downstream molecules, multiplying the signal through the pathway.
02How can faulty cell-cycle control contribute to cancer?
Cells can bypass checkpoints and continue dividing despite DNA damage or other stop signals.
03How does insulin illustrate negative feedback?
High blood glucose triggers insulin release, and insulin promotes glucose uptake, bringing blood glucose toward its set point.
04Why do different cell types respond differently to the same signal?
They may have different receptors, relay proteins, or target genes.
05How does mitosis preserve chromosome number?
Duplicated sister chromatids separate so each daughter nucleus receives one copy of every chromosome.
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