Signal Transduction Question and Answer Flashcards

What is signal transduction?

The process by which information from the extracellular environment is conveyed to the interior of the cell.

What is a ligand in signal transduction?

A signaling molecule that combines with ligand receptors to initiate cellular responses.

What determines if a cell responds to a specific ligand?

Only cells that express the receptor for that specific ligand will respond.

How do lipophilic signal molecules behave?

They diffuse through the cell membrane and bind to cytosolic or nuclear receptors.

How do lipophobic signal molecules function?

They bind to receptors on the surface of the cell membrane.

What types of responses do lipophilic signals typically induce?

Slower responses related to changes in gene activity.

What are the major types of membrane-bound receptors?

7 TM receptors, Single TM receptors with intrinsic kinase activity, ion channels.

What functions do receptor tyrosine kinases do?

Receptor tyrosine kinases facilitate the phosphorylation of tyrosine residues, activating signaling pathways.

What is the role of second messengers in signaling pathways?

They help propagate the signal within the cell after the initial receptor-ligand interaction.

Name two common second messengers.

Cyclic AMP (cAMP) and Inositol trisphosphate (IP3).

What is the function of protein kinases?

They add phosphate groups to proteins, modulating their activity.

What do phosphatases do?

They remove phosphate groups from proteins.

Which protein facilitates the release of Ca2+ from intracellular stores?

Inositol trisphosphate (IP3).

What role does calmodulin play in cellular signaling?

It binds Ca2+ to activate various proteins, influencing physiological functions.

What characterizes 7 TM receptors?

They are membrane receptors that span the plasma membrane seven times and associate with G-proteins.

Which family of G proteins stimulates adenylyl cyclase?

Gs family.

What effect does cholera toxin have on G proteins?

It locks the Gs alpha subunit in an active state, continuously stimulating adenylyl cyclase.

Describe the Ras-MAPK signaling pathway.

Activation begins when a growth factor binds to a receptor, leading to a cascade of events that culminates in cellular responses related to growth and proliferation.

What are the effects of cAMP in cells?

It activates protein kinases, leading to modified enzyme activity and various cellular effects.

How does insulin stimulate glucose uptake?

By activating the PI3K-Akt signaling pathway, which translocates GLUT4 to the plasma membrane.

What does the JAK-STAT pathway do?

Regulates gene transcription in response to growth factors.

How does steroid hormone action typically work?

They bind intracellular receptors and promote gene transcription.

What is the function of GTP in signal transduction?

It acts as a molecular switch in G-protein activation.

How does activation of phospholipase C affect calcium levels?

It produces IP3, which releases Ca2+ from the endoplasmic reticulum.

What role does nitric oxide play in vasodilation?

It stimulates guanylyl cyclase to produce cGMP, leading to muscle relaxation.

What happens to intracellular cAMP levels after G protein activation?

They increase due to the conversion of ATP by adenylyl cyclase.

What can lead to the activation of protein kinase C?

Diacylglycerol (DAG) as a second messenger.

What is the general structure of receptor tyrosine kinases?

They have an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular catalytic domain.

What does the term 'cross-phosphorylation' refer to?

The process where receptor subunits phosphorylate each other upon ligand binding.

How does the binding of growth factors alter receptor function?

It induces conformational change, leading to autophosphorylation and activation.

What is the primary outcome of insulin receptor activation?

Increased glucose uptake in muscle and fat cells.

What does PDK phosphorylate?

Akt, activating it in the PI3K-Akt signaling pathway.

Mention a key physiological response mediated by Ca2+ signaling.

Muscle contraction.

What is the role of calmodulin in muscle contraction?

It activates calcium-dependent kinases that regulate muscle function.

What does the activation of guanylate cyclase produce?

Cyclic guanosine monophosphate (cGMP).

How do agonists and antagonists differ in their effect on receptors?

Agonists activate receptors while antagonists block their activity.

What is the significance of the SH2 domain?

It recognizes phosphorylated tyrosine residues in signaling proteins.

What is a possible consequence of overactivation of the PI3K-Akt pathway?

Increased cell proliferation and survival, linked to cancer.

What is the role of PDE (phosphodiesterase) in cellular signaling?

It regulates levels of cyclic nucleotides by catalyzing their degradation.

What does insulin receptor substrate (IRS) do?

It acts as a docking site for signaling proteins after receptor activation.

How is phospholipase C activated?

Through the activation of G proteins following receptor-ligand interaction.

What physiological process does nitric oxide trigger?

Vasodilation in blood vessels.

Define 'cross talk' in the context of signal transduction.

Interactions among different signaling pathways that influence cellular responses.

How do multiple receptors interact with the same ligand?

Different receptors can elicit different responses to the same signaling molecule.