Chapter 29 Self-test questions

. Which of the following signalling molecules binds to a receptor situated in the cytosol, rather than the outer membrane of the cell?

Progesterone.

Adrenaline (Epinephrine).

Epidermal growth factor.

Interferon.

. What is the first event which happens to a growth factor/ cytokine receptor after binding its cognate signal molecule?

Binding of signal activates the receptor's cytosolic tyrosine kinase domain.

Binding of signal causes the receptor to pick up a tyrosine kinase from the cytosol.

Binding of signal causes receptors to dimerise.

Binding of signal causes tyrosines in the receptor's C-terminal tail to become phosphorylated.

. What type of protein is Ras?

A tyrosine kinase.

A serine-threonine kinase.

A small monomeric GTPase switch protein.

A G protein switch.

. Which of the following signals does not activate a serpentine receptor which in turn activates a heterotrimeric G-protein?

Glucagon.

Insulin.

Light in retinal rod and cones cells.

Vasopressin.

. Which second messenger signals the release of Ca⁺⁺ from the endoplasmic reticulum?

Cyclic AMP.

Cyclic GMP.

1,2 diacyl glycerol.

Inositol triphosphate.

. Insulin receptor substrates IRS 1 /2 are phosphorylated by the receptor tyrosine kinase domain. What would happen if the IRS 1/2 were phosphorylated on a serine/threonine residue?

The insulin signal would be prematurely terminated leading to insulin resistance.

The ras pathway would be activated prematurely and the insulin signal amplified.

The PI 3-kinase pathway would be activated prematurely and insulin metabolic effects would be amplifies.

GLUT 4 transporters would remain fixed on the cell membrane and would not be able to be internalised.

. In cholera, there is uncontrolled secretion of sodium ions and water into the intestinal lumen because of the action of cholera toxin on a G protein coupled receptor system. How does the toxin act?

Cholera toxin activates a Gi (inhibitory) protein.

Cholera toxin inhibits phosphodiesterase so that the signal is not switched off.

Cholera toxin inhibits the binding of vasoactive intestinal polypeptide to the receptor.

Cholera toxin inhibits the GTPase activity of the G protein alpha subunit.

. When it activates the Ras signal transduction pathway, the function of the activated receptor is to locate a GDP-GTP exchange protein close to the membrane where the Ras protein is located.

True

False

. Which of the following enzymes is activated by cyclic AMP, passing on the hormonal signal?

Protein kinase A.

Protein kinase B.

Protein kinase C.

G protein receptor kinase.

. Which of the following hormones cross the cell membrane by virtue of being lipid soluble?

Thyroid hormones.

Oestrogen.

Retinoic acid.

Insulin.

. Akt/PKB which is involved in the insulin signalling cascade is an example of which type of enzyme?

A serine/threonine kinase.

A tyrosine kinase.

A phosphorylase.

A phosphodiesterase.

. How does Akt/PKB activate glycogen synthesis?

By inactivating glycogen synthase kinase by phosphorylation.

By activating phosphodiesterase by phosphorylation.

By activating Ras by phosphorylation.

By activating protein kinase A (PKA) by phosphorylation.

Chapter 29 Self-test questions

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