cell signaling past + generated questions

1) The insulin signaling pathway includes which of the following steps?

a) ligand-induced dimerization of the receptor

b) phosphorylation of IRS proteins

c) phosphorylation of SH2 domains

d) IRS dimerization

Correct answer: B

A) false insulin receptors are already dimerized, binding of insulin leads to conformational change and autophosphorylation

C) SH2 domains are protein interaction modules, and do not become phosphorylated themselves

D) IRS proteins do not dimerize, they remain as monomers for docking

Cytochromes P450 (CYP proteins) are:

a) a superfamily of enzymes that typically act as monooxygenases

b) hemoproteins approximately 450 nm in greatest dimension

c) mitochondrial enzymes that require 02 and ATP as cofactors for hydroxylation processes

d) lipophilic molecules subjected to phosphorylation by NADPH

Correct answer: A)

B) this refers to absorption peak not dimensions

C) 2 things are wrong 1) not all are mitochondrial some are bound to ER and 2) ATP—> NADPH

D) hydroxylate nod phosphorylated, NADPH reduces it doesn’t phosphorylate

Which of the following statements is true of the cAMP molecule?

a) when active, it is bound to cGMP

b) is activated by Gq proteins

c) is inhibited through phosphorylation by PKB

d) is included in pathways with (beta)-adrenergic receptors

Correct answer: D)

A) they are 2 different nucleotides which do not bind to each other

B) Gq proteins activate Phospholipase C

C) neither of these are actions of PKB on cAMP, rather it is regulated by adenylate cyclase an phosphodiesterases

Heat Shock Proteins (HSPs) may

a) catalyze the degradation of hormone receptors by hydrolytic cleavage of the ligand binding domain (LBO)

b) hamper the DNA-binding function in steroid hormone receptors

c) mediate cell signaling by conveying pregnenolone in the bloodstream

d) mediate the binding of plasma membrane phospholipids to glucocorticoid receptors.

Correct answer: B)

A) They stabilize proteins, prevent misfolding, and assist folding, not degrade them. They act as chaperones not proteases.

B) TRUE

C) Pregnenolone transport in blood is via lipoproteins or carrier proteins, not HSPs

D) HSPs interact with the receptor protein, not plasma membrane phospholipids

The bacterial pathogen B. pertussis impairs the functioning of signal transduction mechanisms

in target cells through

a) secretion of ADP toxins

b) endocytosis of JAK-STAT receptors

c) molecular deactivation of target G.i proteins

d) ADP-acetylation of target nuclear proteins

Correct answer: C)

A) too general —> ADP-ribosylating toxin targeting G_i

B) involved in cytokine signaling but not main target of pertussis

C) true

D) ADP-ribosylation not acetylation, G proteins not nuclear proteins

Which of the following statements is true of primary bile acids?

a) They are conjugated to isocaproaldehyde in liver cells.

b) They are found conjugated with Liver X Receptors (LXR) in the bile.

c) They are synthetized from cholesterol in the liver cells.

d) They bind cholesterol to form secondary bile acids in liver cells.

Correct answer: C)

A) conjugated with taurine and glycine

B) LXR receptors are conjugated with taurine and glycine and are not present in bile

C) TRUE

D) this happens in small intestine by action of bacteria not cholesterol

Which of the following statements is true of heterotrimeric G-proteins?

a) They catalyse the reaction: ATP > CAMP + PPi

b) They combine with membrane GPCRs.

c) They are activated by cGDP.

d) They can synthesize GTP when stimulated by GAP.

Correct answer: B)

A) catalyzed by adenylate cyclase not G proteins

B) TRUE

C) activated by GTP

D) g proteins are not involved in GTP synthesis but RAS is

Which of the following is not a signaling molecule that acts as a ligand of a hormone receptor?

a) Insulin.

b) Adenylyl cyclase.

c) Triiodothyronine.

d) Progesterone.

Correct answer: B)

A) acts as ligament for insulin receptor (eg. Insulin pathway)

B) CORRECT

C) acts on nuclear thyroid hormone receptor

D) acts as ligand for progesterone hormone receptor

Which of the following is the abbreviation for an intracellular second messenger?

a) GABA

b) GS3K

c) NOS

d) STAT

Correct answer: D)

A) extracellular messenger ==> neurotransmitter

B) enzyme not messenger

C) this is an enzyme not a second messenger

D) TRUE

What’s targeted by cAMP

a) PKA

b) PLA

c) PKC

d) PDK1

Correct answer: A

A) -

B) activated by Ca2+ and othersignals not including cAMP

C) activated by DAG and Ca2+ in IP3-DAG pathway

D) activated by PIP3 in PI3K-Akt pathway

What works on 7TMRS?

a) NO

b) Glucagon

c) Insulin

d) Testosterone

Correct answer: B)

A) diffuses across membrane and activates soluble guanylyl cyclase

B) -

C) binds to insulin receptors —> tyrosine kinase receptors

D) binds to intracellular receptors

Insulin:

a) Forms a zinc hexamer with glutamate residues

b) It is secreted from pancreatic β-cells when glucose level is low

c) Formed by two peptide chains linked with disulfide bridges

d) Excreted through GLUT-4 to the blood

Correct answer: C)

A) histidine residues not glutamate residues

B) when glucose levels are high since it promotes the export of glut transporters to cell surface

C)

D) glut4 transport glucose andare regulazed by insulin theydo not temselvestransport insulin

Which is not an abbreviation for an intracellular second messenger?

a) DAG

b) PIP3

c) HRE

d) cGMP

Correct answer: C)

A) activates PKC after being formed from PIP2

B) recruitsPDK1 and Akt to membrane

C) -

D) formed from GTP by guanylyl cyclase and mediates the NO and natriuretic peptide signaling

Steroid vs peptide hormone characteristic:

a) Steroids are hydrophilic while peptides are not

b) Steroids control gene expression while peptides does not

c) Hormones are water soluble and peptides are not

d) Peptide hormones link to membrane receptors and steroids to intracellular receptors

Correct answer: D

A) its actually the other way aroundmeaning peptides (hydrphilic) cannot cross the membrane while steroid (lipophilic) can

B) both can the only difference is one does it directly (steroids) and another indirectly (peptides) e.g cAMP

C) once again it is opposite. Peptide hormones are generally hydrophilic hence water soluble. While steroid are the opposite.

D) -