signal transduction pathway

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

• Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP

• Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of glycogen to glucose

• Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol

• Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the endocytotic vesicle

Which of the following is correct about signal transduction pathways?

• Signal transduction pathways are found only in the cells of the most complex animals

• Signal transduction pathways have evolved recently along the development of enlarged brain size in mammals

• In the signal transduction pathways, a single molecule can stimulate the release of thoundsands of molecules of product within a cell

• Signal transduction pathways are unique in that receptors that stimulate the pathway are located only on the surface of a plasma membrane

Which of the following correctly describes the response stage of this signal transduction pathway?

• epinephrine binds to a g-protein coupled receptor protein present in the cell membrane
• the g protein changes shape, is activated, activates adenyl cyclase, which activates cAMP, which activates protein kinases
• cAMP binds to the g-protein coupled receptor protein
• glycogen synthesis is inhibited and glycogen breakdown is promoted