Cell Signaling & Second Messengers

These flashcards cover key concepts and details regarding cell signaling processes, second messengers, and the biochemical mechanisms involved in various signaling pathways.

What are the basic components of a signaling reaction?

Releasing cell, signaling molecule (ligand), target cell, and receptor.

What are the two classifications of signaling molecules?

Lipophilic and peptide ligands.

How do you distinguish between membrane-bound and intracellular receptors?

They differ in their location, structure, and function.

What pathways are involved in G protein-coupled receptors?

Gs, Gi, Gq, receptor enzymes, and second messengers.

What do cholera and pertussis toxins regulate?

They regulate adenylyl cyclase.

What does Ras signaling affect?

It affects cell proliferation, differentiation, and vesicle transport.

What is an example of a receptor with intrinsic tyrosine kinase activity?

Insulin receptor.

What are significant adaptor molecules involved in signaling?

Ras, STATs, and phosphatidylinositol 3-kinase (PI3).

What cytokines are activated by nonreceptor tyrosine kinases?

Interleukins and interferons.

What is the role of protein kinase A?

Activation of various proteins through phosphorylation.

What does cAMP stand for?

Cyclic adenosine monophosphate.

Which signaling molecule activates protein kinase A?

cAMP.

What is the role of adenylyl cyclase?

It converts ATP to cAMP.

What does the term 'efficacy' mean in pharmacology?

The ability of a drug to produce a response.

Which type of signaling involves ligands acting on the cell that secreted them?

Autocrine signaling.

What is an example of an endocrine hormone?

Insulin.

What type of signal transduction mechanism do G-protein coupled receptors use?

They use GTP-binding proteins.

What role does calcium (Ca2+) play in signaling?

It acts as a second messenger in various pathways.

What happens to adenylyl cyclase activity in Gi protein signaling?

It decreases.

What causes receptor desensitization?

Prolonged exposure to a signaling molecule.

What effect does insulin have on glucose uptake?

It promotes glucose uptake in cells.

What defines a ligand-gated ion channel?

It opens or closes in response to a ligand binding.

What is the result of adrenergic receptor stimulation?

Increased heart rate and vasodilation.

What is the role of phospholipase C in Gq protein signaling?

It hydrolyzes phospholipids to produce second messengers IP3 and DAG.

What is myasthenia gravis?

An autoimmune disorder that affects nicotinic acetylcholine receptors.

When does receptor up-regulation occur?

In response to decreased levels of ligand.

What type of receptors do steroid hormones bind to?

Intracellular receptors.

What is the result of nitric oxide signaling?

Increased levels of cGMP leading to vasodilation.

What happens inside the cell when an agonist binds to a receptor?

An effector is activated, leading to intracellular signaling.

What is the function of growth factors?

They stimulate cell growth and proliferation.

What kind of receptors do catecholamines bind to?

G protein-coupled receptors.

What is the function of cGMP in vascular smooth muscle?

It facilitates relaxation and vasodilation.

What is the significance of the Gα subunit in G-protein signaling?

It catalyzes GTP hydrolysis, ending the signaling pathway.

How does tamoxifen act as a selective estrogen receptor modulator?

It blocks estrogen receptors in breast tissue.

Which signaling pathway do insulin and growth factors utilize?

Intrinsic tyrosine kinase pathways.

What role does calmodulin play in cellular signaling?

It mediates effects of intracellular calcium.

What are the primary roles of the Gs protein?

Stimulates adenylyl cyclase and increases cAMP.

What is Ras activation associated with?

Stimulation of the MAP kinase pathway.

What does phosphodiesterase do to cAMP?

Converts it to 5'-AMP, thereby reducing its levels.

Which receptors are involved in nitric oxide signaling?

Guanylyl cyclase receptors.

What does a receptor with intrinsic tyrosine kinase activity do?

Phosphorylates tyrosine residues on itself and other proteins.

How is nitric oxide produced?

By endothelial cells in response to shear stress.

What is the primary effect of Gq protein activation?

Activation of phospholipase C, producing IP3 and DAG.

What is the function of the PI3 kinase pathway?

To promote cell survival and growth.

Which enzymes do G proteins regulate?

Adenylyl cyclase and phospholipase C.

What happens to a cell upon receptor desensitization?

It becomes less responsive to the signaling molecule.

How does activation of protein kinase C (PKC) occur?

Through DAG and calcium signaling.

What is the role of SH2 domains in adaptor proteins?

They bind to phosphorylated tyrosine residues.

What is a hallmark of cancer related to Ras mutations?

Unregulated cell division.

What is the main action mechanism of glucagon?

Stimulates glycogen breakdown.

What does the term 'ligand' refer to in receptor biology?

A signaling molecule that binds to a receptor.

What is the function of a receptor antagonist?

Blocks the action of a natural ligand.

How do receptor tyrosine kinases (RTKs) signal?

By activating intrinsic kinase activities upon ligand binding.

What gives rise to steroid signaling pathways?

Hormone binding to intracellular receptors.

What is a key result of binding calcium to calmodulin?

Activation of various cellular enzymes.

What does the G-protein activation cascade initiate?

Signal transduction pathways involving second messengers.

What is meant by 'stereospecific binding' in relation to receptors?

Receptors selectively bind to specific molecular shapes or isomers.

Explain the term 'hydrophobic signaling molecule.'

Molecules that can easily diffuse through the membrane to bind to intracellular receptors.

How does cholera toxin affect cellular signaling?

It prevents Gαs from hydrolyzing GTP, causing continuous cAMP production.

What is important about the structure of G-protein coupled receptors?

They have seven transmembrane domains.

What is meant by 'conformational change' in receptors?

The alteration in receptor shape upon ligand binding, leading to activation.

What types of hormones use nuclear receptors?

Lipid-soluble hormones such as steroid hormones and thyroid hormones.

What process does cGMP primarily mediate?

Vasodilation and relaxation of vascular smooth muscle.

Which receptors act through intracellular pathways but do not have intrinsic enzymatic activity?

Non-receptor tyrosine kinases.

What characterizes the signaling of growth factors?

They usually activate signaling cascades that regulate growth and division.

What type of cells does insulin primarily act on?

Muscle, adipose, and liver cells.

How does receptor dimerization impact signaling?

Dimerization activates tyrosine kinase activity, leading to further signaling.

What is the effect of voltage-gated ion channels on cellular activity?

They change ion flow in response to changes in membrane potential.

What is a potential clinical application for inhibiting steroid hormone synthesis?

Treatment of hormone-responsive cancers.

What is the primary function of G protein-coupled receptors (GPCRs)?

To mediate cellular responses to various external signals.

What does the term 'receptor internalization' refer to?

The process where receptors are drawn into the cell after prolonged stimulation.

What are second messengers in the context of signaling?

Molecules like cAMP, IP3, and DAG that relay signals within the cell.

What type of channel do benzodiazepines interact with?

Ligand-gated ion channels.

What role does the endoplasmic reticulum (ER) play in calcium signaling?

It releases calcium in response to IP3 signaling.

How do vitamin D and retinoic acid function in the body?

As nuclear hormone receptors regulating gene expression.

What type of signaling pathway is activated by insulin?

The PI3 kinase pathway.

How do G proteins terminate their signaling activity?

By hydrolyzing GTP to GDP.

In which parts of the cell do steroid hormones typically exert their effects?

In the cytoplasm and nucleus.

What is the consequence of disturbing the balance of intracellular calcium?

It can lead to various cellular dysfunctions or disease states.

What is the result of increased cAMP levels in cells?

Enhanced protein kinase A activity and diverse physiological effects.

How do receptor antagonists differ from agonists?

Antagonists inhibit receptor activity, while agonists stimulate it.