Cell-Cell Communication in Biology Wk12

What is cell signaling?

Communication between cells and tissues that coordinates responses and involves signal transduction.

What is signal transduction?

The process by which an extracellular signal is transmitted across the membrane, initiating an intracellular change or response.

How did ancestral signaling molecules evolve?

They likely evolved in prokaryotes and single-celled eukaryotes, later adopted by multicellular descendants.

What is quorum sensing?

A process that allows bacteria to sense local population density through a concentration of signaling molecules.

What are cell junctions?

Structures that directly connect the cytoplasm of adjacent animal and plant cells, allowing signaling substances to pass freely.

What is local signaling in multicellular organisms?

Communication via direct contact or signaling molecules between nearby cells.

What is long-distance signaling?

Communication using hormones that travel through the circulatory system to target cells.

What is endocrine signaling?

A type of long-distance signaling where specialized cells release hormones that travel to target cells.

What triggers synaptic signaling?

An electrical signal that causes the release of neurotransmitters.

What is autocrine signaling?

A form of signaling where a cell signals itself.

What are the three stages of cell signaling?

1. Reception: signaling molecule binds to a receptor. 2. Transduction: signal is carried along a pathway. 3. Response: signal triggers a cellular response.

What happens during the reception stage of cell signaling?

A signaling molecule binds to a specific receptor protein, causing it to change shape.

What are G protein-coupled receptors (GPCRs)?

Receptors that activate G proteins upon binding with signaling molecules, initiating a signaling cascade.

What is the role of receptor tyrosine kinases?

They bind signaling molecules and, upon activation, phosphorylate tyrosine residues on themselves and other proteins.

What are ion channel receptors?

Receptors that open or close in response to signaling molecules, allowing ions to flow across the membrane.

What characterizes intracellular receptors?

They are activated by small or hydrophobic chemical messengers that can cross the membrane, such as steroids.

What is a phosphorylation cascade?

A multistep process in signal transduction where a series of proteins are phosphorylated, amplifying the signal.

What are second messengers?

Small, non-protein, water-soluble molecules or ions that spread throughout a cell by diffusion and participate in signaling pathways.

What is cyclic AMP (cAMP)?

A widely used second messenger that is produced from ATP by adenylyl cyclase in response to an extracellular signal.

How do calcium ions function as second messengers?

When released into the cytosol, they can cause significant changes in cellular responses due to their low baseline concentration.

What is the significance of scaffolding proteins in signaling?

They enhance signaling efficiency by grouping proteins involved in the same pathway and may help activate relay proteins.

What are the five aspects of signal regulation?

1. Specificity of the response. 2. Amplification of the signal. 3. Diversity of responses. 4. Efficiency of response. 5. Termination of the signal.

What is signal amplification?

The process where one signaling molecule can activate multiple downstream molecules, enhancing the overall response.

What is the role of termination in cell signaling?

It involves inactivation mechanisms that reset the signaling system when the concentration of external signaling molecules decreases.

What is the function of inositol triphosphate (IP3) and diacylglycerol (DAG)?

They are additional second messengers involved in signaling pathways, particularly in the release of calcium ions.

What is the output response in cell signaling?

The final activated molecule in the signaling pathway may regulate transcription, enzyme synthesis, ion channel activity, or cell metabolism.