Question 1

Which of the following best describes the initial event that occurs when a ligand binds to a receptor tyrosine kinase (RTK)?

Accepted Answer

The RTK dimerizes, bringing two kinase domains into close proximity.

Question 2

What is the primary function of the intracellular tyrosine kinase domain in RTKs?

Accepted Answer

To phosphorylate tyrosine residues on itself and other proteins.

Question 3

Which of the following statements about RTK dimerization is CORRECT?

Accepted Answer

Dimerization of RTKs is triggered by ligand binding to the extracellular domain.

Question 4

After RTK dimerization and autophosphorylation, which domain on downstream proteins typically recognizes and binds to the phosphorylated tyrosine residues?

Accepted Answer

SH2 domain

Question 5

Which of the following is NOT a characteristic of receptor tyrosine kinases (RTKs)?

Accepted Answer

They activate G proteins by exchanging GDP for GTP.

Question 6

What is the role of autophosphorylation in RTK signaling?

Accepted Answer

It creates binding sites for downstream signaling proteins.

Question 7

A mutation prevents the phosphorylation of tyrosine residues on an RTK. Which of the following is the most likely consequence?

Accepted Answer

Downstream SH2 domain-containing proteins will not bind to the RTK.

Question 8

Which sequence of events correctly describes RTK activation and downstream signaling?

Accepted Answer

Ligand binding → dimerization → autophosphorylation → SH2 protein binding

Question 9

Which of the following equations correctly represents the phosphorylation reaction catalyzed by RTKs?

Accepted Answer

$$\mathrm{Protein{-}Tyr} + \mathrm{ATP} \rightarrow \mathrm{Protein{-}Tyr{-}P} + \mathrm{ADP}$$

Question 10

A patient has a mutation in the SH2 domain of a signaling protein. Which process is most likely to be disrupted?

Accepted Answer

Binding to phosphorylated tyrosine residues on activated RTKs

Question 11

Which of the following best explains why RTK activation can lead to a variety of cellular responses?

Accepted Answer

Phosphorylated tyrosines on RTKs recruit different SH2 domain-containing proteins, activating multiple signaling pathways.

Question 12

Which of the following is a direct result of SH2 domain-containing protein binding to phosphorylated RTKs?

Accepted Answer

Initiation of downstream signaling cascades

Question 13

A researcher adds a drug that blocks ATP binding to the kinase domain of an RTK. What is the most immediate effect?

Accepted Answer

The RTK cannot autophosphorylate its tyrosine residues.

Question 14

Which of the following best describes the role of ligand-induced dimerization in RTK activation?

Accepted Answer

It brings two kinase domains together, allowing cross-phosphorylation.

Question 15

Which of the following is a common misconception about RTK signaling?

Accepted Answer

RTKs phosphorylate serine and threonine residues.

Receptor Tyrosine Kinases (RTKs) and Signal Transduction

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