Front

What is a signaling molecule?

Back

A signaling molecule, also known as a ligand, is a chemical substance that transmits signals to cells, triggering a response.

Front

Where do signaling molecules bind?

Back

Signaling molecules bind to specific receptors on the surface of target cells.

Front

What is a ligand?

Back

A ligand is a type of signaling molecule that binds to receptors to initiate a cellular response.

Front

What is a secondary messenger?

Back

A secondary messenger is a molecule that relays signals received from receptors on the cell surface to target molecules inside the cell.

Front

Give an example of a secondary messenger.

Back

Calcium ions (Ca²⁺) are an example of a secondary messenger.

Front

What role does calcium play in muscle contraction?

Back

Calcium ions bind to proteins in muscle cells, triggering contraction.

Front

Where is calcium stored in muscle cells?

Back

Calcium is stored in the smooth endoplasmic reticulum (smooth ER) of muscle cells.

Front

How is calcium released from the smooth ER?

Back

Calcium is released from the smooth ER through gated ion channels.

Front

What is the function of gated ion channels?

Back

Gated ion channels regulate the flow of ions across the cell membrane in response to signals.

Front

What is the difference between a ligand and a substrate?

Back

A ligand is a signaling molecule that binds to receptors, while a substrate is a molecule upon which an enzyme acts.