Question

1- Nonreceptor tyrosine kinases are:

Select one:

a. Transmembrane receptors

b. Membrane proteins with no enzymatic activity

c. Enzymes that phosphorylate serine and threonine residues

d. Peripheral membrane enzymes that associate with receptors

e. Inhibitors of transmembrane receptors

2- Which of the following statements about MAP kinase pathways is FALSE?

Select one:

a. MAP kinases phosphorylate serine and threonine residues

b. MAP kinases can be activated by tyrosine kinases

c. MAP kinases are present in all eukaryotic cells

d. MAP kinases are involved in cell differentiation

e. MAP kinases have nonspecific target proteins

3- Which of the following statements best describe most of the pathways?

Select one:

a. Once a receptor is activated, it directly targets the destination protein.

b. Once a receptor is activated, it causes a cytosolic protein to be activated, which then phosphorylates another enzyme, and so on, until the destination protein is reached.

c. Once a receptor is activated, the receptor is endocytosed in a vesicle, which then fuses with an endosome, which ultimately fuses with a lysosome to release the ligand.

d. Once a receptor is activated, the bound receptor travels to the nucleus with the ligand to activate transcription

e. Once a receptor is activated, ligand-gated channels open to release ions down the gradient.

Answer 1

1st question-

correct answer is option D.

Explanation- non receptors tyrosine kinase are enzymes (not receptors nor the inhibitor of transmembrane receptors as mentioned in other options . These enzymes add a phosphate group to tyrosine residue not to serine or threonine residue

2nd question-

correct option is option e

Explanation- option e is false because MAP kinase pathway are specific and specifically phosphorylate serine and threonine at their specific receptors.

3rd question-

option b is correct.

Explanation- most of the signaling pathway are started with activation of receptors. Once the receptor is activated, it then phosphorylate other enzymes one by one untill the signal reaches the destination