AP Biology Unit 4: Cell Communication

What is a receptor?

A protein that binds a signal molecule and triggers a cellular response.

Why don’t all cells respond to the same signal?

Only cells with the correct receptor can respond.

What is long-distance signaling?

Cell communication where signals travel through the bloodstream to distant target cells.

Give an example of a long-distance signaling molecule.

Hormones such as epinephrine or insulin.

What is short-distance signaling?

Communication between nearby cells, often requiring direct contact.

How do immune cells communicate?

Through direct cell-to-cell contact using surface proteins (ex: MHC and T-cell receptors).

What is a transcription factor?

A protein that binds DNA and turns genes on or off.

What does the SRY gene do?

Produces a transcription factor that activates genes for male development.

What hormone activates the epinephrine signaling pathway?

Epinephrine.

What is the overall effect of epinephrine on muscle cells?

Breaks down glycogen to release glucose.

What protein is activated first after epinephrine binds its receptor?

G-protein.

What enzyme produces cAMP?

Adenylyl cyclase.

What is cAMP?

A second messenger that relays and amplifies signals inside the cell.

What enzyme is activated by cAMP?

Protein Kinase A (PKA).

What enzyme breaks glycogen into glucose-1-phosphate?

Glycogen phosphorylase.

What is signal amplification?

When enzymes activate other enzymes, increasing the strength of the signal.

Why are second messengers important?

They allow a small signal to create a large cellular response.

What happens to blood glucose during exercise?

Blood glucose levels increase.

How does epinephrine affect pancreatic cells?

Activates alpha cells and inhibits beta cells.

Which hormone is released by alpha cells?

Glucagon.

Which hormone is released by beta cells?

Insulin.

What are plasmodesmata?

Channels that connect plant cells and allow direct signal transfer.

Why are plasmodesmata important?

They allow fast communication without signals leaving the cell wall.

Can different pathways use the same second messenger?

Yes, pathways can share second messengers like cAMP.