GPCR Function and Significance Quiz

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Questions and Answers

What is the significance of the fact that GPCRs constitute the single largest protein superfamily encoded by animal genomes?

It indicates that GPCRs have evolved to be highly efficient in their function.
It demonstrates the importance of GPCRs in drug discovery. (correct)
It implies that GPCRs are particularly susceptible to mutations.
It suggests that GPCRs are essential for a wide range of cellular processes. (correct)

Why are G protein-coupled receptors (GPCRs) also referred to as seven-transmembrane receptors?

They are activated by seven distinct signaling pathways.
They have seven transmembrane domains that span the cell membrane. (correct)
They interact with seven different G proteins.
They are involved in seven major cellular processes.

What is the implication of the finding that inactivating mutations in GPCRs are linked to over 30 human diseases?

GPCRs play a critical role in maintaining human health. (correct)
Mutations in GPCRs are a common cause of disease.
GPCRs are highly susceptible to mutations.
GPCRs are the primary targets for drug development.

Which of the following is NOT an example of a natural ligand that binds to GPCRs?

Enzymes (D) Signup and view all the answers

What is the function of olfactory sensory neurons in vertebrates?

They detect and transmit signals related to smell. (A) Signup and view all the answers

What is the significance of the similarity between the odorant-binding pocket in OR51E2 and the binding pockets of other class A GPCRs?

It indicates that these receptors share similar ligand binding properties. (A), It suggests a common evolutionary origin for these receptors. (B) Signup and view all the answers

What is the role of Gαs in the activation of OR51E2?

Gαs activates adenylyl cyclase, which converts ATP to cAMP. (C) Signup and view all the answers

What is the likely consequence of a mutation in the transmembrane domain of an odorant receptor?

All of the above. (D) Signup and view all the answers

What is the function of adenylate cyclase in the context of the provided text?

Adenylate cyclase catalyzes the synthesis of cAMP from ATP. (B) Signup and view all the answers

What is the primary function of the transmembrane domain bundle (TM) in the AC9-Gαs complex?

The TM domain is responsible for transmitting the signal across the plasma membrane. (A) Signup and view all the answers

What does the term 'heterotrimeric' refer to in the context of G proteins?

The G protein is composed of three different subunits, α, β, and γ. (C) Signup and view all the answers

The text mentions a change in conformation in the receptor molecule. What does this change in conformation directly lead to?

The release of GDP from the Gα subunit. (E) Signup and view all the answers

Which of the following statements accurately describes the role of the α subunit in the G protein?

The α subunit binds to guanine nucleotides and undergoes conformational changes upon activation. (C) Signup and view all the answers

What is the significance of the lipid chains attached to the α and γ subunits of the G protein?

They anchor the G protein to the plasma membrane. (D) Signup and view all the answers

The activation of a single receptor can lead to the activation of multiple G protein molecules. This phenomenon is referred to as:

Signal amplification. (D) Signup and view all the answers

Based on the content, what can be inferred about the role of the AC9-Gαs complex in cellular signaling?

The complex is involved in the synthesis and regulation of cAMP. (C) Signup and view all the answers

What is the primary function of phospholipids in cell membranes?

To provide structural integrity and impermeability (B) Signup and view all the answers

Which of the following is NOT a lipid-derived second messenger?

cGMP (C) Signup and view all the answers

What is a growth factor?

A naturally occurring substance that stimulates cellular growth and differentiation (B) Signup and view all the answers

How do growth factors typically act on their target cells?

By binding to specific receptors on the cell surface and triggering a signaling cascade (D) Signup and view all the answers

What is the significance of the increase in phosphoinositides levels in cells treated with growth factors?

It suggests that a signaling pathway involving phosphoinositides is activated (A) Signup and view all the answers

Which of the following statements about phospholipids is TRUE?

Phospholipids are essential components of cell membranes and signaling pathways (A) Signup and view all the answers

What is the most likely outcome of a mutation that prevents the production of a specific growth factor?

The cell will stop responding to growth factors (B) Signup and view all the answers

Why are growth factors important for cellular development?

They regulate cell division and specialization (B) Signup and view all the answers

What is the role of cyclic AMP (cAMP) in the breakdown of glycogen?

cAMP activates a protein kinase which phosphorylates phosphorylase, leading to glycogen breakdown. (B) Signup and view all the answers

What is the significance of the 'substance' identified by Sutherland as cyclic AMP?

It acts as a second messenger, transmitting the signal from the hormone to phosphorylase. (B) Signup and view all the answers

In the context of the described experiment, why was the hormone-treated particulate fraction washed and the wash added to the supernatant?

To isolate the substance released by the particulate fraction upon hormone treatment. (B) Signup and view all the answers

What is the primary function of the protein kinase activated by cAMP, in the context of glycogen breakdown?

Bind to and activate phosphorylase, initiating glycogen breakdown. (A) Signup and view all the answers

Which of the following statements accurately describes the role of a second messenger in cell signaling?

Second messengers act as intermediaries, relaying the signal from the hormone to intracellular targets. (C) Signup and view all the answers

What is the key difference between the hormone and the second messenger (cAMP)?

The hormone binds to the cell surface receptor, while cAMP acts inside the cell. (B) Signup and view all the answers

How does the activation of phosphorylase lead to glycogen breakdown?

By directly breaking down glycogen into glucose monomers. (C) Signup and view all the answers

What is a plausible explanation for the observation that the hormone-treated particulate fraction, when washed and its wash added to the supernatant, activated phosphorylase?

The wash contained a substance released by the particulate fraction that, upon hormone binding, activated phosphorylase. (C) Signup and view all the answers

What is the specific phosphoinositide that FYVE and PX domains bind to?

PI-3-P (A) Signup and view all the answers

What is the role of the PLC isoforms in phospholipid binding?

They recognize and bind to specific phosphoinositides and diacylglycerol. (C) Signup and view all the answers

Which of the following domains is NOT involved in phosphoinositide recognition?

EF (A) Signup and view all the answers

What is the term used for the family of enzymes that catalyze the phosphorylation of the 3-position of the inositol ring in phosphoinositides?

PI3K (B) Signup and view all the answers

Which phosphoinositide is specifically recognized by pleckstrin homology (PH) domains?

All of the above (D) Signup and view all the answers

Which of the following is true about the interaction of FYVE and PX domains with membranes?

They interact with both polar and hydrophobic regions of the membrane. (C) Signup and view all the answers

What is the role of enzymes like PTEN and SHIP in PI metabolism?

They act as lipid phosphatases, removing phosphate groups from phosphoinositides. (D) Signup and view all the answers

What is the primary function of phosphoinositide kinases in PI metabolism?

They add phosphate groups to phosphoinositides. (D) Signup and view all the answers

Which of the following enzymes are involved in the dephosphorylation of key tyrosine residues (pY) on cyclin-dependent kinases (cdks)?

CDC25s (C) Signup and view all the answers

What is the significance of the CX5R signature in the context of dual-specificity phosphatases (DSPs)?

It indicates that DSPs can dephosphorylate both tyrosine and serine/threonine residues. (D) Signup and view all the answers

Which type of phosphatase utilizes Asp-based catalysis?

A fourth family of phosphatases (B) Signup and view all the answers

What is the role of FCP/SCP in the regulation of RNA polymerase II?

FCP/SCP dephosphorylates specific serine residues on the C-terminal domain of RNA polymerase II. (D) Signup and view all the answers

What is the primary role of the phosphorylation state of the C-terminal domain (CTD) of RNA polymerase II?

It regulates the elongation of nascent RNA transcripts. (C) Signup and view all the answers

What is the primary function of LMWPTPs?

They dephosphorylate phosphoinositides, mRNA, and serine/threonine residues. (A) Signup and view all the answers

Which of the following statements is TRUE about the phosphorylation of the C-terminal domain (CTD) of RNA polymerase II?

It involves multistep phosphorylation at Ser2, Ser5, and Ser7. (D) Signup and view all the answers

Why are dual-specificity phosphatases (DSPs) known as a diverse bunch?

They can dephosphorylate a wide range of substrates, including phosphoinositides, mRNA, and even serine and threonine residues. (D) Signup and view all the answers

Flashcards

G Protein-Coupled Receptors (GPCRs)

Membrane proteins that interact with G proteins and have 7 transmembrane helices.

Natural ligands

Molecules like hormones and neurotransmitters that bind to GPCRs to activate them.