AP Bio U4 - Cell Communication and Cell Cycle

Target cell

A cell that receives and responds to a chemical signal.

Ligand

A chemical messenger that cannot pass through the membrane and binds to a receptor on the cell surface, often activating a G protein.

G protein

A membrane-embedded protein with multiple subunits that is activated when a ligand binds to a receptor.

cAMP

A secondary messenger that spreads throughout the cell and activates target protein kinases.

Protein kinase

An enzyme that adds phosphate groups to other proteins (phosphorylation), activating them.

Adenylyl cyclase

An enzyme that becomes active when the G protein alpha subunit binds, converting ATP into cyclic AMP (cAMP).

Epinephrine

A ligand that binds to a protein receptor on the cell membrane, starting the signal transduction pathway.

How do cells communicate directly with adjacent cells?

By sending chemical signals through cell membrane or cell wall modifications that allow communication between touching cells.

What is short-distance (local) cell signaling?

When a cell releases local regulators that affect nearby target cells, usually of the same type.

What is long-distance cell signaling?

When a signal travels far from the signaling cell to reach a target cell, often of a different type.

What is a signal transduction pathway?

The process by which a message is received, converted into an intracellular signal, and leads to a cellular response

What are the two main types of signal transduction?

Protein modification and phosphorylation cascade.

What is a phosphorylation cascade?

A series of steps where a phosphate group carrying energy is passed from one molecule to another, often involving protein kinases, until a final action occurs.

What happens during the reception step of cell signaling?

A ligand binds to a receptor on the cell membrane, causing the receptor to change shape.

What is transduction in cell signaling?

The process of converting an extracellular signal into an intracellular message.

What are the three main steps of cell signaling?

Reception, transduction, and response.

How does G protein activation work?

Ligand binding causes a shape change in the G protein, releasing the alpha subunit, which moves to adenylyl cyclase.

How is protein kinase regulated?

Its regulatory subunits keep the catalytic portion inactive until cAMP binds, which releases the catalytic portion.

How is the catalytic portion of protein kinase activated?

It is activated by phosphorylation with energy from ATP.

What is the function of protein kinase once activated?

It transfers phosphate to target proteins like phosphorylase, which triggers glucose release inside the cell.

What is the role of the G protein alpha subunit?

It is released upon activation and interacts with adenylyl cyclase to generate cAMP.

What is the final action of the signal transduction pathway triggered by epinephrine?

Activation of protein kinase, which phosphorylates target proteins to produce the cellular response.