Chapter 11 Cell Communication

What is a signal transduction pathway?

A process by which a signal on a cell's surface is converted to a specific cellular response in a series of steps.

What role does paracrine signaling play in cellular communication?

Secreting cells send regulators to target cells and to all cells in the vicinity, influencing local cellular responses.

How does synaptic signaling operate?

Electrical signals trigger chemical signals that specifically affect only target cells, such as neurotransmitters.

What is the role of reception in signal transduction?

Detection of the signaling molecule by a cell.

What is transduction in the context of signal transduction pathways?

The process where the signal is converted to a form that brings about a specific cellular response.

What happens in the response stage of signal transduction?

The transduced signal triggers some sort of cellular response.

What is a ligand?

A molecule that specifically binds to another, usually larger molecule.

What activates a G protein?

A signaling protein activates a receptor, which changes shape and allows the G protein to bind to the enzyme.

Why is the GTPase activity of a G protein important?

It stops the signal by converting GTP back to GDP.

What does a kinase enzyme do?

Catalyzes the transfer of phosphate groups.

How does tyrosine kinase function in signal transduction?

It allows for the activation of many signal transduction pathways.

What is a key difference between receptor kinases and G protein-coupled receptors?

Receptor kinases can activate more signal transduction pathways than G protein-coupled receptors.

Fill in the blank: Each activated protein in tyrosine kinase triggers a signal pathway leading to a response.

Transduction… cellular.

In which body system are ligand-gated ion channels and voltage-gated ion channels particularly important?

Nervous system.

Where are intracellular receptors found in a cell?

In the cytoplasm or nucleus, bonding with chemical messengers that are hydrophobic or very small.

What are transcription factors?

Molecular complexes that control which genes are turned on and transcribed to mRNA.

What are two benefits of multistep pathways in signal transduction?

Amplification of signal and better regulation.

What is the role of protein kinase in a cell?

Transfers phosphate groups from ATP to proteins.

What do protein phosphatases do?

They remove phosphate groups from proteins.

What is the difference between a first messenger and a second messenger in signaling?

The first messenger is the ligand; the second messenger is any small, non-protein component of a signal transduction pathway.

What is the role of cAMP in cellular signaling?

cAMP activates protein kinase A, leading to cellular responses.

Explain the mechanism of disease in cholera related to signaling pathways.

The G protein cannot hydrolyze GTP to GDP, leading to constant activation of cAMP and excessive salt release due to osmosis, resulting in diarrhea.

What are three pathways often induced by calcium ions?

Pathways via mitochondria, endoplasmic reticulum (ER), and plasma membrane.

What happens to the cytoplasmic concentration of calcium when it functions as a second messenger?

It increases.

When cell signaling causes a response in the nucleus, what typically occurs?

Proteins become transcription factors, which choose certain genes to be transcribed.

When cell signaling causes a response in the cytoplasm, what typically occurs?

Regulation of activity of proteins.

How do scaffolding proteins enhance a cellular response?

They enhance speed and accuracy by reducing the rate of response limitation due to diffusion.

What happens to a cell during the process of apoptosis?

DNA is chopped up, the cell shrinks, lobes up, vesicles form, and digestion occurs by scavenger cells.

Give one example of an external signal for apoptosis and two examples of internal signals.

External: death signaling molecule activates Ced-9. Internal 1: leaking from mitochondria. Internal 2: ER stress due to excessive misfolding of proteins.