Chapter 11 Biology

What is a signal transduction pathway?

Process by which a signal on a cell’s surface is converted to a specific cellular response in a series of steps.

How does a yeast mating serve as an example of a signal transduction pathway?

Alpha yeast sends alpha signals that A yeast receives. A yeast sends A signals that only alpha can receive. The respective signals are then transduced and a response is carried out (mating).

Paracrine signaling

Secreting cells sends regulators to target cells and to all cells in the vicinity. Examples are animal cells and growth hormones.

Synaptic signaling

Electrical signals trigger chemical signal. Very specific; affects only target cell. Examples are neurotransmitters.

How does a hormone qualify as a long-distance signaling example?

Hormones can travel to any part of the body via the circulatory system.

Reception

Detection of signaling molecule

Transduction

Signal converted to form that can bring about a specific cellular response.

Response

Transduced signal triggers some sort of cellular response.

Ligand

Molecule that specifically binds to another, usually bigger molecule.

What activates a G protein?

Signaling protein activates receptor receptor changes shape G protein binds to enzyme.

A G protein is also a GTPase enzyme. Why is this important?

It stops the signal and converts GTP back to GDP

What does a kinase enzyme do?

Catalyzes transfer of phosphate groups.

How does tyrosine kinase function in the membrane receptor?

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 a lot more signal transduction pathways than just the one that G protein-coupled receptors can.

Each activated protein in tyrosine kinase triggers a signal ______ pathway leading to a ______ response.

Transuction… cellular

In what body system are ligand-gated ion channels and voltage-gated ion channels of particular importance?

Nervous system

Intracellular receptors are found in the ______ or ______ of the cell, where they bond to chemical messengers that are _____ or very small, like nitric acid.

Cytoplasm… nucleus… hydrophobic

What are transcription factors?

They are molecule complexes that control which genes are turned on and transcribed to mRNA

What are two benefits of multistep pathways?

Amplification of signal, and better regulation.

What is the role of protein kinase?

Transfer phosphate groups from ATP to proteins.

What is the role of protein phosphatases?

Remove phosphate groups from proteins.

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

First messenger is the ligand, second messenger is any small, non-protein components of a signal transduction pathway.

What is the role of cAMP?

cAMP activates protein kinase A, which causes a cellular response.

Explain the mechanism of disease in cholera.

G protein cannot hydrolyze GTP to GDP enzyme that the G protein activates is always on cAMP constantly is being produced salt is constantly released as a cellular response due to osmosis, diarrhea.

List three pathways often induced by calcium ions.

Pathway via mitochondria, ER, and plasma membrane.

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

It increases.

When cell signaling causes a response in the nucleus, what normally happens?

Proteins become transcription factors, certain genes are chosen, these are then transcribed.

When cell signaling causes a response in the cytoplasm, what normally happens?

Regulation of activity of proteins.

How do scaffolding proteins enhance a cellular response?

Enhancement of speed and accuracy because the rate of response is no longer limited by rate of diffusion.

What specifically happens to a cell during the process of apoptosis?

DNA chopped up, cell shrinks, lobes up, vesicles form, digestion by scavenger cells.

Give one example of signal for apoptosis coming from outside the cell, and two from inside the cell.

Out: death signaling molecule reactions with protein and activates Ced-9. IN1: Leaking form mitochondria. IN2: ER due to excessive missfolding of proteins.