Cell signaling

Why do cells need signaling?

Cells need signaling to respond to their environment and coordinate activities such as growth, division, metabolism, movement, differentiation, and apoptosis.

What is a ligand?

A signaling molecule that binds to a receptor protein to initiate a signaling pathway.

What are the three major stages of cell signaling?

Reception, Transduction, and Response.

What is direct cell-to-cell communication?

Communication through direct physical connections, such as gap junctions, plasmodesmata, and septal pores.

What is contact-dependent signaling?

A form of signaling where the signaling molecule remains attached to the signaling cell's surface and requires physical contact with the target cell.

What is paracrine signaling?

Signaling where cells release molecules that diffuse to nearby cells.

What is endocrine signaling?

A type of signaling involving hormones released into the bloodstream that travel long distances to target cells.

How do neurons signal?

Neurons transmit signals using electrical impulses and neurotransmitters that travel across synapses.

What are cell-surface receptors?

Proteins embedded in the plasma membrane that detect signals that cannot cross the lipid membrane.

What are intracellular receptors?

Receptors located inside the cell that detect molecules that can pass through the membrane.

What are ligand-gated ion channels?

Receptors that open ion channels when a ligand binds to them, allowing ions to flow across the membrane.

What are G-protein coupled receptors (GPCRs)?

The largest receptor family in humans, involved in various cellular processes and act as molecular switches.

What is the process of GPCR activation?

The binding of a ligand leads to a change in the receptor's shape, activating the G protein by exchanging GDP for GTP.

What are second messengers?

Small molecules inside the cell that relay signals quickly and amplify the cellular response.

What is the cAMP signaling pathway?

A common signaling pathway where GPCR activation leads to the production of cAMP from ATP, activating protein kinase A.

How is the cAMP signal turned off?

Phosphodiesterase breaks down cAMP into AMP, stopping the activation of protein kinase A.

What is the IP3/DAG pathway?

A signaling pathway where activation of GPCRs leads to the production of IP3 and DAG, triggering calcium release from the endoplasmic reticulum.

What are receptor tyrosine kinases (RTKs)?

Receptors that function as enzymes to add phosphate groups to tyrosine residues when activated, leading to multiple signaling pathways.

What is signal amplification?

The process where a single signaling event produces a dramatic effect through the activation of multiple molecules in a signaling pathway.

What are mechanisms of signal termination?

Processes that stop signaling to maintain balance, including ligand dissociation, receptor internalization, and degradation of second messengers.

What is the big picture of cell signaling?

Cell signaling converts external information into cellular action through a flow of information: signal molecule → receptor → intracellular signaling → cellular response.