AP Biology Cell Communication

cAMP usually directly activates __________.

• protein kinase A

• phosphodiesterase

• receptor tyrosine kinases

• G proteins

• adenylyl cyclase

What event would activate a G protein?

• replacement of GDP with GTP

• hydrolysis of GTP to GDP

• hydrolysis of GDP to GTP

• phosphorylation of GDP to GTP

• phosphorylation of GTP to GDP

Ras, a small G protein located at the plasma membrane, is often mutated in different types of cancer. Ras normally signals to a cell that it should divide. Cancer cells divide uncontrollably. Which of the following changes to Ras would you expect to see in a cancer cell that has mutated Ras present?

• a mutation that means Ras cannot hydrolyze GTP to GDP

• a mutation that leads to Ras being sent to the endomembrane system

• a mutation that means Ras cannot bind to GTP

• a mutation that means GDP is constantly bound to Ras

• a mutation in which Ras cannot bind to its GPCR

Tags

NGSS.HS-LS3-2

A mutation in the active site of adenylyl cyclase that inactivates it would most likely lead to __________.

• an increase in the amount of cAMP present in the cell

• higher activity of protein kinase A

• reduced binding of adenylyl cyclase to protein kinase A

• lower activity of protein kinase A

• increased binding of adenylyl cyclase to the G protein that activates it

Testosterone does not affect all cells of the body because __________.

• testosterone cannot cross the plasma membrane

• not all cells have cytoplasmic receptors for testosterone

• not all cells in the body have membrane receptors for testosterone

• it is a local regulator

• it affects only cells that have ion-channel receptors

Second messengers tend to be water-soluble and small. This accounts for their ability to __________.

• rapidly cross the plasma membrane

• pass quickly from cell to cell

• move from substrate to substrate during a phosphorylation cascade

• rapidly move throughout the cell by diffusion

• cross the nuclear membrane and interact with DNA

Phosphorylation __________.

• always inactivates a protein

• activates G-protein-linked receptors

• can either activate or inactivate a protein

• is accomplished by protein phosphatases

• always activates a protein

A G protein is active when __________.

• GDP replaces GTP

• it is bound by its ligand and transported to the nucleus

• it is phosphorylated by protein kinase

• GTP is bound to it

• Ca2+ binds to a G-protein-linked receptor

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because __________.

• only target cells retain the appropriate DNA segments

• most cells lack the Y chromosome required

• only target cells possess the cytosolic enzymes that transduce the testosterone

• only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor

• intracellular receptors are present only in target cells

The cellular response of a signal pathway that terminates at a transcription factor would be __________.

• the synthesis of mRNA

• the activation of an inactive enzyme

• alteration of the cytoskeleton

• a change in the chemical composition of the cytosolic environment

• the activation of a metabolic pathway