Question 1

Which of the following statements is TRUE?

Accepted Answer

A)  Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. 
B)  Ca2+ is not a second messenger. 
C)  Phosphodiesterase converts GMP into cGMP 
D)  Conversion of ATP to cAMP is a phosphorylation reaction. 
E)  Phospholipase C converts ATP to cAMP. 
A)  Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. 
B)  Ca2+ is not a second messenger. 
C)  Phosphodiesterase converts GMP into cGMP 
D)  Conversion of ATP to cAMP is a phosphorylation reaction. 
E)  Phospholipase C converts ATP to cAMP. A

Question 2

The enzyme that catalyzes the production of cAMP from ATP is phosphodiesterase.

Accepted Answer

A) True 
 B)False  False

Question 3

Eicosanoids are a family of ubiquitous, fatty-acid-derived, local chemical messengers.

Accepted Answer

A) True 
 B)False  True

Question 4

Amplification of a second-messenger cascade can take place at which level of a signal cascade?

Accepted Answer

A)  One activated receptor can activate numerous G-proteins. 
B)  One activated G-protein can activate numerous effector enzymes. 
C)  One active effector enzyme can catalyze numerous reactions. 
D)  One activated protein kinase can allosterically modulate numerous proteins. 
E)  All of the choices are correct. 
A)  One activated receptor can activate numerous G-proteins. 
B)  One activated G-protein can activate numerous effector enzymes. 
C)  One active effector enzyme can catalyze numerous reactions. 
D)  One activated protein kinase can allosterically modulate numerous proteins. 
E)  All of the choices are correct.

Question 5

What second messenger most directly causes calcium ions to be released from intracellular stores?

Accepted Answer

A)  diacylglycerol 
B)  adenylyl cyclase 
C)  inositol triphosphate 
D)  phospholipase A 
E)  phospholipase C 
A)  diacylglycerol 
B)  adenylyl cyclase 
C)  inositol triphosphate 
D)  phospholipase A 
E)  phospholipase C

Question 6

Which of the following are ways in which binding of an intercellular chemical messenger with a cell's receptor can bring about a cellular response?

Accepted Answer

A)  opening or closing of specific ionic channels in the plasma membrane 
B)  activation of an intracellular second-messenger system 
C)  promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins 
D)  activating or inhibiting intracellular enzymes 
E)  All of the choices are correct. 
A)  opening or closing of specific ionic channels in the plasma membrane 
B)  activation of an intracellular second-messenger system 
C)  promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins 
D)  activating or inhibiting intracellular enzymes 
E)  All of the choices are correct.

Question 7

Competition for receptors is strictly a pharmacological phenomenon, since naturally occurring chemical messengers do not compete with each other for the same receptor site.

Accepted Answer

A) True 
 B)False

Question 8

Two cell types having the same type of receptor for a chemical messenger will always respond to that messenger in the same way.

Accepted Answer

A) True 
 B)False

Question 9

At very low concentrations, epinephrine causes an artery to dilate. At higher concentrations epinephrine causes the same artery to constrict. How can these different effects be explained?

Accepted Answer

A)  There is one type of epinephrine receptor that uses two second-messenger systems. 
B)  There are two types of epinephrine receptors with different affinities for epinephrine that use two different second-messenger systems. 
C)  There are two types of receptors for epinephrine that use the same second-messenger system. 
D)  At higher concentrations epinephrine can pass through the plasma membrane and directly stimulate contraction within the cell. 
A)  There is one type of epinephrine receptor that uses two second-messenger systems. 
B)  There are two types of epinephrine receptors with different affinities for epinephrine that use two different second-messenger systems. 
C)  There are two types of receptors for epinephrine that use the same second-messenger system. 
D)  At higher concentrations epinephrine can pass through the plasma membrane and directly stimulate contraction within the cell.

Question 10

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a ____________ and cAMP is a _____________.

Accepted Answer

A)  ligand, receptor 
B)  first messenger, hydrophobic hormone 
C)  second messenger, ion channel 
D)  first messenger, second messenger 
E)  enzyme, second messenger 
A)  ligand, receptor 
B)  first messenger, hydrophobic hormone 
C)  second messenger, ion channel 
D)  first messenger, second messenger 
E)  enzyme, second messenger

Question 11

Second messengers:

Accepted Answer

A)  are necessary for all receptor signal transduction mechanisms. 
B)  act in the cell cytoplasm. 
C)  only function as intercellular messengers. 
D)  always function to activate enzymes. 
E)  are always proteins. 
A)  are necessary for all receptor signal transduction mechanisms. 
B)  act in the cell cytoplasm. 
C)  only function as intercellular messengers. 
D)  always function to activate enzymes. 
E)  are always proteins.

Question 12

Which of these is a lipid-soluble messenger?

Accepted Answer

A)  thyroid hormone 
B)  protein kinase 
C)  glucose 
D)  sodium 
E)  cyclic AMP 
A)  thyroid hormone 
B)  protein kinase 
C)  glucose 
D)  sodium 
E)  cyclic AMP

Question 13

In which situation would an injected drug be the most effective agonist for an endogenous chemical messenger?

Accepted Answer

A)  The drug has a lower affinity for the messenger's receptors than the messenger does. 
B)  The drug achieves 50% saturation of the messenger's receptors at a lower concentration than that required by the messenger. 
C)  The drug does not couple to the binding site of the messenger's receptor. 
D)  The drug binds to an alternate binding site on the protein receptor and reduces its affinity for the endogenous chemical messenger. 
A)  The drug has a lower affinity for the messenger's receptors than the messenger does. 
B)  The drug achieves 50% saturation of the messenger's receptors at a lower concentration than that required by the messenger. 
C)  The drug does not couple to the binding site of the messenger's receptor. 
D)  The drug binds to an alternate binding site on the protein receptor and reduces its affinity for the endogenous chemical messenger.

Question 14

Cyclic AMP activates allosteric proteins.

Accepted Answer

A) True 
 B)False

Question 15

Aspirin and other nonsteroidal anti-inflammatory drugs are more specific in their effects on eicosanoid synthesis than are steroidal anti-inflammatory drugs.

Accepted Answer

A) True 
 B)False

Question 16

Specificity is an important characteristic of intercellular communication; which of these best explains how it occurs?

Accepted Answer

A)  The phospholipid composition of the plasma membrane differs among cells. 
B)  Protein receptors are only located on the surface of target cells. 
C)  All cells have the same DNA, so any cell can express protein receptors for a specific chemical. 
D)  Chemical messengers are all proteins, so bind only to receptors that are proteins. 
E)  Protein receptors for chemical messengers are only expressed in specific target cells. 
A)  The phospholipid composition of the plasma membrane differs among cells. 
B)  Protein receptors are only located on the surface of target cells. 
C)  All cells have the same DNA, so any cell can express protein receptors for a specific chemical. 
D)  Chemical messengers are all proteins, so bind only to receptors that are proteins. 
E)  Protein receptors for chemical messengers are only expressed in specific target cells.

Question 17

First messengers may bind to a membrane receptor that is an ion channel, which promotes a change in membrane polarity.

Accepted Answer

A) True 
 B)False

Question 18

Phosphorylation is a necessary component of any enzyme activation.

Accepted Answer

A) True 
 B)False

Question 19

Activated calmodulin functions to activate or inactivate cytosolic enzymes.

Accepted Answer

A) True 
 B)False

Question 20

Cocaine lowers the levels of a chemical messenger in the brain called enkephalin. Researchers have found the number of enkephalin receptors to be higher in cocaine addicts than nonaddicted people. This is an example of

Accepted Answer

A)  saturation. 
B)  up-regulation. 
C)  antagonism. 
D)  affinity. 
E)  down-regulation. 
A)  saturation. 
B)  up-regulation. 
C)  antagonism. 
D)  affinity. 
E)  down-regulation.

Which of the following statements is TRUE?

The enzyme that catalyzes the production of cAMP from ATP is phosphodiesterase.

Eicosanoids are a family of ubiquitous, fatty-acid-derived, local chemical messengers.

Amplification of a second-messenger cascade can take place at which level of a signal cascade?

What second messenger most directly causes calcium ions to be released from intracellular stores?

Which of the following are ways in which binding of an intercellular chemical messenger with a cell's receptor can bring about a cellular response?

Competition for receptors is strictly a pharmacological phenomenon, since naturally occurring chemical messengers do not compete with each other for the same receptor site.

Two cell types having the same type of receptor for a chemical messenger will always respond to that messenger in the same way.

At very low concentrations, epinephrine causes an artery to dilate. At higher concentrations epinephrine causes the same artery to constrict. How can these different effects be explained?

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a and cAMP is a _.

Second messengers:

Which of these is a lipid-soluble messenger?

In which situation would an injected drug be the most effective agonist for an endogenous chemical messenger?

Cyclic AMP activates allosteric proteins.

Aspirin and other nonsteroidal anti-inflammatory drugs are more specific in their effects on eicosanoid synthesis than are steroidal anti-inflammatory drugs.

Specificity is an important characteristic of intercellular communication; which of these best explains how it occurs?

First messengers may bind to a membrane receptor that is an ion channel, which promotes a change in membrane polarity.

Phosphorylation is a necessary component of any enzyme activation.

Activated calmodulin functions to activate or inactivate cytosolic enzymes.

Cocaine lowers the levels of a chemical messenger in the brain called enkephalin. Researchers have found the number of enkephalin receptors to be higher in cocaine addicts than nonaddicted people. This is an example of

Homeostasis: a Framework for Human Physiology

Chemical Composition of the Body and Its Relation to Physiology

Cellular Structure, Proteins, and Metabolic Pathways

Movement of Molecules Across Cell Membranes

Neuronal Signaling and the Structure of the Nervous System

Sensory Physiology

Consciousness, the Brain, and Behavior

Muscle

Control of Body Movement

The Endocrine System

Cardiovascular Physiology

Respiratory Physiology

The Kidneys and Regulation of Water and Inorganic Ions

The Digestion and Absorption of Food

Regulation of Organic Metabolism and Energy Balance

Reproduction

The Immune System

Filters

Exam 5: Cell Signaling in Physiology

Which of the following statements is TRUE?

The enzyme that catalyzes the production of cAMP from ATP is phosphodiesterase.

Eicosanoids are a family of ubiquitous, fatty-acid-derived, local chemical messengers.

Amplification of a second-messenger cascade can take place at which level of a signal cascade?

What second messenger most directly causes calcium ions to be released from intracellular stores?

Which of the following are ways in which binding of an intercellular chemical messenger with a cell's receptor can bring about a cellular response?

Competition for receptors is strictly a pharmacological phenomenon, since naturally occurring chemical messengers do not compete with each other for the same receptor site.

Two cell types having the same type of receptor for a chemical messenger will always respond to that messenger in the same way.

At very low concentrations, epinephrine causes an artery to dilate. At higher concentrations epinephrine causes the same artery to constrict. How can these different effects be explained?

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a ____________ and cAMP is a _____________.

Second messengers:

Which of these is a lipid-soluble messenger?

In which situation would an injected drug be the most effective agonist for an endogenous chemical messenger?

Cyclic AMP activates allosteric proteins.

Aspirin and other nonsteroidal anti-inflammatory drugs are more specific in their effects on eicosanoid synthesis than are steroidal anti-inflammatory drugs.

Specificity is an important characteristic of intercellular communication; which of these best explains how it occurs?

First messengers may bind to a membrane receptor that is an ion channel, which promotes a change in membrane polarity.

Phosphorylation is a necessary component of any enzyme activation.

Activated calmodulin functions to activate or inactivate cytosolic enzymes.

Cocaine lowers the levels of a chemical messenger in the brain called enkephalin. Researchers have found the number of enkephalin receptors to be higher in cocaine addicts than nonaddicted people. This is an example of

Homeostasis: a Framework for Human Physiology

Chemical Composition of the Body and Its Relation to Physiology

Cellular Structure, Proteins, and Metabolic Pathways

Movement of Molecules Across Cell Membranes

Neuronal Signaling and the Structure of the Nervous System

Sensory Physiology

Consciousness, the Brain, and Behavior

Muscle

Control of Body Movement

The Endocrine System

Cardiovascular Physiology

Respiratory Physiology

The Kidneys and Regulation of Water and Inorganic Ions

The Digestion and Absorption of Food

Regulation of Organic Metabolism and Energy Balance

Reproduction

The Immune System

Filters

Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a and cAMP is a _.