Cell Receptor Practice Questions

Which of the following is a characteristic of G protein–coupled receptors (GPCRs)?

• A. They work directly as enzymes.

• B. They consist of a single polypeptide chain that crosses the lipid bilayer seven times.

• C. They open ion channels directly.

• D. They phosphorylate proteins without intermediary complexes.

B. They consist of a single polypeptide chain that crosses the lipid bilayer seven times.

What happens to the alpha subunit of the G-protein when a ligand binds to a GPCR?

• A. It binds GDP and becomes inactive.

• B. It remains in an inactive state bound to GTP.

• C. It binds GTP and becomes active.

• D. It dissociates from the G-protein and binds directly to the ligand.

C. It binds GTP and becomes active.

Which second messenger is synthesized from ATP by adenylyl cyclase when GPCRs are activated?

• A. cGMP

• B. cAMP

• C. PIP2

• D. IP3

B. cAMP

Cholera can be caused by the ADP ribosylation of which subunit of the G-protein?

• A. β-subunit

• B. γ-subunit

• C. α-subunit

• D. All subunits

C. α-subunit

Which enzyme is activated by cAMP to exert its effects inside the cell?

• A. Protein kinase C

• B. Adenylyl cyclase

• C. Phospholipase C

• D. Protein kinase A (PKA)

D. Protein kinase A (PKA)

What is the function of phospholipase C-β (PLCβ) in GPCR signaling?

• A. It activates adenylyl cyclase.

• B. It cleaves PIP2 into IP3 and diacylglycerol.

• C. It binds to GTP and activates downstream signaling.

• D. It dephosphorylates cAMP.

B. It cleaves PIP2 into IP3 and diacylglycerol.

Which of the following is true about receptor tyrosine kinases (RTKs)?

• A. They use G-proteins to relay the signal.

• B. Ligand binding causes receptor chains to dimerize and undergo transautophosphorylation.

• C. They phosphorylate serine residues in downstream proteins.

• D. They degrade cAMP after signal transduction.

B. Ligand binding causes receptor chains to dimerize and undergo transautophosphorylation.

Which signaling module is activated by Ras in receptor tyrosine kinase pathways?

• A. PLCβ

• B. MAP kinase module (Raf, Mek, Erk)

• C. Phosphodiesterase

• D. JAK/STAT pathway

B. MAP kinase module (Raf, Mek, Erk)

The JAK/STAT signaling pathway is associated with which type of receptors?

• A. Ion-channel coupled receptors

• B. G-protein coupled receptors

• C. Tyrosine kinase-associated receptors

• D. Serine-Threonine kinase receptors

C. Tyrosine kinase-associated receptors

Which receptor type is known for phosphorylating proteins on serine or threonine residues instead of tyrosine residues?

• A. Receptor tyrosine kinases

• B. G-protein coupled receptors

• C. Serine-Threonine kinase receptors

• D. Receptor tyrosine phosphatases

C. Serine-Threonine kinase receptors

What is the primary role of diacylglycerol (DAG) in GPCR signaling?

• A. It activates protein kinase A (PKA).

• B. It binds and opens calcium channels.

• C. It assists in prostaglandin synthesis and activates protein kinase C (PKC).

• D. It deactivates adenylyl cyclase.

C. It assists in prostaglandin synthesis and activates protein kinase C (PKC).

Which of the following is responsible for raising calcium concentration in the cytosol during GPCR signaling?

• A. Diacylglycerol (DAG)

• B. IP3-gated Ca2+ channels in the endoplasmic reticulum

• C. cAMP activation of Ca2+ pumps

• D. GTP hydrolysis by the alpha subunit of the G-protein

B. IP3-gated Ca2+ channels in the endoplasmic reticulum

What type of receptor directly synthesizes cGMP after ligand binding?

• A. GPCRs

• B. Receptor tyrosine kinases (RTKs)

• C. Guanylyl cyclase receptors

• D. Tyrosine phosphatases

C. Guanylyl cyclase receptors

The Ras protein belongs to which family of proteins?

• A. Serine-threonine kinases

• B. Tyrosine phosphatases

• C. GTPases

• D. Adenylyl cyclases

C. GTPases

In the Ras-Raf-MAPK signaling pathway, what happens when Ras is bound to GTP?

• A. Ras remains inactive.

• B. Ras becomes active and initiates a signaling cascade.

• C. Ras dissociates from the receptor and inhibits downstream signaling.

• D. Ras binds to ATP and triggers phosphorylation.

B. Ras becomes active and initiates a signaling cascade.

What is the result of "trans autophosphorylation" in receptor tyrosine kinases (RTKs)?

• A. The receptor activates the G-protein.

• B. The receptor chains phosphorylate each other on tyrosine residues.

• C. cAMP is produced by adenylyl cyclase.

• D. The ligand dissociates from the receptor.

B. The receptor chains phosphorylate each other on tyrosine residues.

Which domain is essential for proteins to bind to the phosphorylated sites on receptor tyrosine kinases (RTKs)?

• A. SH2/SH3 domain

• B. GTP-binding domain

• C. ATP-binding domain

• D. IP3-binding domain

A. SH2/SH3 domain

Which of the following describes the JAK/STAT pathway?

• A. Ligand binding to the receptor activates Ras, which then activates MAPK.

• B. JAK phosphorylates the receptor and STAT proteins, which translocate to the nucleus.

• C. Adenylyl cyclase is activated, producing cAMP, which activates PKA.

• D. Phospholipase C is activated, generating DAG and IP3.

B. JAK phosphorylates the receptor and STAT proteins, which translocate to the nucleus.

Receptor tyrosine phosphatases are characterized by which type of activity?

• A. They phosphorylate tyrosine residues on downstream proteins.

• B. They remove phosphate groups from tyrosine residues.

• C. They synthesize cGMP from GTP.

• D. They activate adenylyl cyclase.

B. They remove phosphate groups from tyrosine residues.

Which receptor type is associated with SMAD signaling?

• A. G-protein coupled receptors

• B. Receptor tyrosine kinases (RTKs)

• C. Serine-Threonine kinase receptors

• D. Receptor tyrosine phosphatases

C. Serine-Threonine kinase receptors

What happens when a ligand binds to a G-protein coupled receptor (GPCR)?

o A) The receptor directly opens an ion channel.

o B) The receptor activates a G-protein, which then activates or inactivates a separate enzyme or channel.

o C) The receptor itself acts as an enzyme.

o D) The receptor undergoes trans autophosphorylation.

B) The receptor activates a G-protein, which then activates or inactivates a separate enzyme or channel.

Which of the following is NOT a major class of cell surface receptors?

o A) Ion-channel coupled receptors

o B) G-protein coupled receptors

o C) Enzyme-coupled receptors

o D) Nuclear receptors

D) Nuclear receptors

What happens when a ligand binds to an enzyme-coupled receptor?

o A) The receptor directly opens an ion channel.

o B) The receptor activates a G-protein.

o C) The receptor itself acts as an enzyme or associates with an enzyme.

o D) The receptor undergoes trans autophosphorylation.

C) The receptor itself acts as an enzyme or associates with an enzyme.

Which of the following is a secondary messenger involved in signal

transduction?

o A) ATP

o B) GTP

o C) cAMP

o D) GDP

C) cAMP

What is the function of phosphodiesterases in cell signaling?

o A) To synthesize cAMP from ATP.

o B) To hydrolyze cGMP into GMP.

o C) To activate protein kinase A (PKA).

o D) To bind and open IP3 gated Ca2+ channels.

B) To hydrolyze cGMP into GMP.

What is the role of protein kinases in intracellular signaling?

o A) To remove phosphate groups from signaling proteins.

o B) To add phosphate groups to signaling proteins.

o C) To bind GTP to signaling proteins.

o D) To hydrolyze GTP to GDP.

B) To add phosphate groups to signaling proteins.

Which type of signaling involves direct cell-to-cell contact?

o A) Paracrine signaling

o B) Endocrine signaling

o C) Autocrine signaling

o D) Juxtacrine signaling

D) Juxtacrine signaling

Which of the following molecules can diffuse through the plasma membrane and bind to intracellular receptors?

o A) Peptide hormones

o B) Amide hormones

o C) Steroid hormones

o D) None of the above

C) Steroid hormones

Which of the following is NOT a secondary messenger?

o A) cAMP

o B) cGMP

o C) Ca2+

o D) ATP

D) ATP

Which type of signaling involves a cell acting on itself?

o A) Paracrine signaling

o B) Endocrine signaling

o C) Autocrine signaling

o D) Juxtacrine signaling

C) Autocrine signaling

Which of the following is a characteristic of endocrine signaling?

o A) It acts on neighboring cells.

o B) It relies on diffusion and act on distant cells.

o C) It involves direct cell-to-cell contact.

o D) It acts on the same cell that produces the signal.

B) It relies on diffusion and act on distant cells.

What type of receptor is the insulin receptor?

o A) G-protein coupled receptor

o B) Ion-channel coupled receptor

o C) Receptor tyrosine kinase

o D) Nuclear receptor

C) Receptor tyrosine kinase

What is the primary function of nuclear receptors?

o A) To bind to cell surface receptors

o B) To act as transcription factors and regulate gene expression

o C) To open ion channels in the plasma membrane

o D) To activate G-proteins

B) To act as transcription factors and regulate gene expression

What happens when a ligand binds to a nuclear receptor?

o A) The receptor undergoes trans autophosphorylation.

o B) The receptor activates a G-protein.

o C) The receptor-ligand complex binds to DNA and regulates gene

expression.

o D) The receptor opens an ion channel.

C) The receptor-ligand complex binds to DNA and regulates gene

expression.

Which of the following is NOT a type of nuclear receptor?

o A) Estrogen receptor

o B) Androgen receptor

o C) Insulin receptor

o D) Thyroid hormone receptor

C) Insulin receptor

What is the primary function of nitric oxide (NO) in the cardiovascular system?

o A) To increase blood pressure

o B) To mediate smooth muscle relaxation and vasodilation

o C) To inhibit platelet aggregation

o D) To activate G-proteins

B) To mediate smooth muscle relaxation and vasodilation

Which enzyme is activated by NO to increase cGMP levels?

o A) Soluble guanylyl cyclase (sGC)

o B) Adenylyl cyclase

o C) Protein kinase G (PKG)

o D) Phosphodiesterase

A) Soluble guanylyl cyclase (sGC)

Which of the following is a downstream effect of cGMP activation?

o A) Increased gluconeogenesis

o B) Smooth muscle contraction

o C) Smooth muscle relaxation

o D) Increased blood pressure

C) Smooth muscle relaxation

What is the effect of NO on renal blood flow?

o A) It decreases renal blood flow.

o B) It has no effect on renal blood flow.

o C) It increases renal blood flow.

o D) It inhibits renal blood flow.

C) It increases renal blood flow.

True or False? Once produced, nitric oxide (NO) can diffuse to neighboring cells.

True

You know that GTP-binding proteins are frequently used in signal transduction as On/off switches. Given that what you know about the mechanism of Vibrio Cholera toxin, what is likely happening in patients suffering with cholera?

• G protein is GDP bound

• Alpha subunit can no longer hydrolyze bound GTP

• Adenylyl cyclase is in an unstimulated state

• Prolonged cessation in cAMP concentration within intestinal cells

Alpha subunit can no longer hydrolyze bound GTP