Deck 5: Chemical Messengers

Question 1

Cells that secrete dopamine must contain which enzymes?

A)tyrosine fi- hydroxylase and dopa decarboxylase
B)dopamine fi- hydroxylase and dopa decarboxylase only
C)dopamine fi- hydroxylase only
D)dopa decarboxylase only
E)tyrosine fi- hydroxylase

Answer 1

A

Question 2

In order to terminate a cAMP- mediated response, the enzyme can be activated to degrade cAMP.

A)cAMP protein kinase
B)cAMP decarboxylase
C)cAMP phosphodiesterase
D)cAMP hydrolase
E)cAMP hydrogenase

Answer 2

C

Question 3

Steroids are released from the secretory cell by

A)simple diffusion.
B)active transport.
C)endocytosis.
D)signal transduction.
E)exocytosis.

Answer 3

A

Question 4

What chemical messenger is released by a presynaptic cell?

A)neurohormone
B)autocrine
C)neurotransmitter
D)hormone
E)paracrine

Question 5

When the alpha subunit of the G protein is activated, it can stimulate ion channels to do what?

A)open only
B)either open or close
C)degrade
D)close only
E)alter the ion that travels through the channel

Question 6

Which of the following enzymes catalyzes synthesis of prostaglandins and thromboxanes?

A)phosphoprotein phosphatase
B)phenylethanolamine N- methyl transferase
C)phospholipase C
D)cyclooxygenase
E)dopamine fi- hydroxylase

Question 7

Which of the following chemical messengers is lipophilic and is therefore able to cross the cell membrane?

A)proteins
B)peptides
C)amino acids
D)eicosanoids
E)amines (excluding thyroid hormone)

Question 8

As a general rule, the magnitude of a target cell's response to a chemical messenger depends on which three factors?

A)(1)the concentration of the messenger, (2)the percent saturation of the receptor, and (3)the specificity of the receptor for the chemical messenger
B)(1)the solubility of the chemical messenger, (2)the location of the receptor, and (3)the class of the receptor
C)(1)the concentration of the messenger, (2)the number of receptors, and (3)the affinity of the receptor for the messenger
D)(1)the solubility of the chemical messenger, (2)the location of the receptor, and (3)the affinity of the receptor to the messenger
E)(1)the half life of the messenger, (2)the number of receptors, and (3)the percent saturation of those receptors

Question 9

Which of the following enzymes catalyzes synthesis of diacylglycerol and inositol triphosphate?

A)dopamine fi- hydroxylase
B)phospholipase C
C)phosphoprotein phosphatase
D)cyclooxygenase
E)phenylethanolamine N- methyl transferase

Question 10

Opening channels for which of the following ions can trigger exocytosis?

A)calcium
B)chloride
C)potassium
D)sodium
E)magnesium

Question 11

Cells that secrete epinephrine must contain which enzymes?

A)phenylethanolamine N- methyl transferase and dopa decarboxylase only
B)dopamine fi- hydroxylase, tyrosine fi- hydroxylase, phenylethanolamine N- methyl transferase, and dopa decarboxylase
C)dopamine fi- hydroxylase, tyrosine fi- hydroxylase, and dopa decarboxylase only
D)tyrosine fi- hydroxylase and phenylethanolamine N- methyl transferase only
E)dopamine fi- hydroxylase and dopa decarboxylase only

Question 12

Thyroid hormones are synthesized from what amino acid?

A)tryptophan
B)tyrosine
C)histidine
D)glutamate
E)glycine

Question 13

Which type of chemical messenger is released into the bloodstream by an endocrine gland where it can affect target cells throughout the body?

A)cytokine
B)paracrine
C)neurotransmitter
D)autocrine
E)hormone

Question 14

Differences in the rate of activity between fast and slow ligand- gated channels are caused by

A)G protein activity gating the fast channel.
B)ligand selectivity.
C)ligand affinity.
D)ligands gating both channels to the closed state.
E)G protein activity gating the slow channel.

Question 15

A half- life, in terms of a chemical messenger, refers to

A)the radioactivity of the chemical messenger.
B)how long the chemical messenger will be effective in the body.
C)the time it takes for half of the chemical messenger in the blood to be degraded.
D)the amount of time it takes to cross the plasma membrane.
E)the amount of time the messenger is bound to a protein.

Question 16

Which of the following enzymes catalyzes synthesis and release of arachidonic acid?

A)phosphodiesterase
B)tyrosine fi- hydroxylase
C)phospholipase A2
D)adenylate cyclase
E)tyrosine kinase

Question 17

A first messenger is an extracellular messenger that binds to its receptor on the _ of the cell and therefore activates a second messenger system.

A)outside
B)ribosome
C)inside
D)G protein
E)endoplasmic reticulum

Question 18

The more specific a drug is for a certain type, the more specific the therapeutic actions of the drug and the fewer the side effects.

A)receptor
B)ligand
C)hormone
D)neurotransmitter
E)target cell

Question 19

In chemical communication between cells, a cell secretes a chemical messenger that binds to on the cell.

A)secretory : receptors : target
B)secretory : connexons : target
C)gap : connexons : secretory
D)target : receptors : secretory
E)secretory : connexons : gap

Question 20

Which of the following statements best describes the function of tyrosine kinase?

A)It catalyzes the formation of dopamine from L- dopa.
B)It catalyzes the formation of norepinephrine from dopamine.
C)It sequesters calcium in the cytosol.
D)It catalyzes the phosphorylation of a protein in the extracellular fluid.
E)It catalyzes the phosphorylation of a protein inside a cell.

Question 21

Androgens are precursor molecules for the synthesis of

A)cortisol.
B)cholesterol.
C)progesterone.
D)estradiol.
E)aldosterone.

Question 22

Which of the following will NOT affect the magnitude of a cell's response to a specific hydrophilic ligand?

A)lipid solubility of the ligand
B)receptor upregulation
C)ligand concentration
D)number of receptors
E)affinity of the receptor for the ligand

Question 23

Which of the following enzymes catalyzes phosphorylation of a protein?

A)adenylate cyclase
B)tyrosine kinase
C)phosphodiesterase
D)phospholipase A2
E)tyrosine fi- hydroxylase

Question 24

Heroin overdose is usually treated with an opioid such as naloxone (Narcan)or naltrexone, an opioid, which prevents heroin from binding to mu receptors and reverses the effects of heroin on the body.

A)antagonist
B)agonist
C)antihistamine
D)ligand
E)second messenger

Question 25

Aspirin decreases inflammation by inhibiting the actions of what enzyme?

A)cyclooxygenase
B)phospholipase A2
C)protein kinase A
D)lipoxygenase
E)dopa decarboxylase

Question 26

Most amines are _, meaning they dissolve in water and therefore cannot cross the cell membrane. The _ _ hormones are an exception because they are _ and can easily cross the cell membrane.

A)amino acids : steroid : lipophilic
B)lipophilic : thyroid : lipophobic
C)lipophobic : thyroid : lipophilic
D)lipophilic : protein : lipophobic
E)hydrophobic : steroid : hydrophilic

Question 27

What enzyme is activated by cAMP?

A)tyrosine kinase
B)protein kinase C
C)phosphodiesterase
D)adenylate cyclase
E)protein kinase A

Question 28

What organelle packages peptide/protein messengers into secretory vesicles?

A)rough endoplasmic reticulum
B)smooth endoplasmic reticulum
C)nucleus
D)lysosomes
E)Golgi apparatus

Question 29

Direct communication between cells in contact with one another is accomplished through

A)paracrine chemical messengers.
B)endocrine hormones.
C)gap junctions.
D)receptors.
E)ligands.

Question 30

Which of the following proteins is directly activated by a G protein?

A)calmodulin
B)phospholipase A2
C)tyrosine kinase
D)adenylate cyclase
E)protein kinase G

Question 31

Eicosanoids are derived from what phospholipid?

A)leukotrienes
B)thromboxanes
C)prostacycline
D)arachidonic acid
E)prostoglandins

Question 32

A(n)is transported in the bloodstream.

A)paracrine
B)glial cell
C)neurotransmitter
D)autocrine
E)hormone

Question 33

In order to synthesize eicosanoids, _ catalyzes the release of _ from a membrane phospholipid.

A)phospholipase C : arachidonic acid
B)phospholipase C : cholesterol
C)phospholipase C : inositol biphosphate
D)phospholipase A2 : cholesterol
E)phospholipase A2 : arachidonic acid

Question 34

When associated with G protein, guanylate cyclase will activate what enzyme?

A)phospholipase C
B)protein kinase A
C)protein kinase C
D)phosphodiesterase
E)protein kinase G

Question 35

The chemical messenger of the nervous system is and chemical messenger of the endocrine system is .

A)hormone : neurotransmitter
B)neurotransmitter : hormone
C)autocrines : paracrines
D)neurohormone : adrenocorticoid
E)neurotransmitter : neurohormone

Question 36

Chronic exposure to a ligand (messenger)the receptor population for that chemical messenger on the target cell.

A)changes the conformation of
B)decreases the affinity of
C)decreases the specificity of
D)down regulates
E)upregulates

Question 37

Which of the following ions binds to calmodulin to ultimately activate a protein kinase?

A)magnesium
B)chloride
C)sodium
D)potassium
E)calcium

Question 38

What molecules are hydrophobic and can easily cross the plasma membrane?

A)lipophobic
B)lipophilic
C)hyperdermic
D)hydrophilic
E)amino acids

Question 39

Which of the following statements is true for the nervous system but NOT the endocrine system?

A)A messenger is transported in the bloodstream.
B)Effector organs are scattered throughout the body.
C)There is a special anatomical arrangement between the secretory cell and the target cell.
D)Communication occurs over long distances.
E)A messenger communicates to target cells by binding to specific receptors.

Question 40

Steroid messengers are derived from what precursor molecule?

A)tyrosine
B)histamine
C)cholesterol
D)arachidonic acid
E)calmodulin

Question 41

What chemical messenger diffuses to neighboring cells to exert an effect?

A)autocrine
B)paracrine
C)neurotransmitter
D)neurohormone
E)hormone

Question 42

Based on your knowledge of signal amplification, which type of chemical messenger can have relatively small concentrations within the bloodstream and still get a large response?

A)paracrine
B)lipophilic
C)lipophobic
D)steroid
E)autocrine

Question 43

Cholera is the leading cause of death in children in developing countries, characterized by massive diarrhea. The effects stem from an extracellular toxin that the bacterium Vibrio cholerae releases into the gut. The toxin acts on a _ that overstimulates which causes a cascade of events that leads to electrolytes leaving the cell and causing water to follow them into the lumen of the intestine, resulting in severe diarrhea.

A)protein- P : GTP
B)G proteins : adenylate cyclase
C)protein kinases : calmodulin
D)cAMP : G proteins
E)calcium : muscles

Question 44

The fi1 adrenergic receptor has the greatest affinity for what messenger?

A)serotonin
B)epinephrine
C)dopamine
D)norepinephrine
E)epinephrine and norepinephrine equally

Question 45

Catecholamines are derived from what amino acid?

A)tyrosine
B)histidine
C)glycine
D)glutamate
E)tryptophan

Question 46

Aspirin is a nonsteroidal anti- inflammatory drug (NSAID)that relieves pain. Which mechanism best describes how NSAIDs work?

A)When aspirin dissolves in the interstitial fluid it causes a concentration gradient and fluid is pulled from the cell reducing inflammation.
B)Aspirin decreases the production of thromboxane A2, a chemical involved in blot clot formation, and COX inhibits A2 and, therefore, blood clots do not form and cause pain.
C)The COX receptors have a greater affinity for aspirin and these speed up the reactions of healing.
D)Prostaglandins (PG)are eicosanoids that produce pain and inflammation. Cyclooxygenase (COX)is an essential enzyme in the production of PG and aspirin inhibits COX and therefore relieves pain due to the reduced production of PG.
E)Leukotrienes are eicosanoids that produce pain and inflammation. COX is used in the lipoxygenase pathway and therefore NSAIDs stop the conversion of arachidonic acid to leukotrienes thereby reducing inflammation.

Question 47

Lipid- soluble molecules are not only hydrophobic, but are also

A)lipophobic.
B)lipophilic.
C)amino acids.
D)disaccharides.
E)cellulose.

Question 48

The target cells of the nervous system are

A)glial cells.
B)other neurons.
C)all the cell types in the body.
D)muscle cells.
E)neurons, muscles, or glands.

Question 49

Which of the following chemical messengers are lipophilic?

A)thyroid hormones
B)steroids
C)peptides/proteins
D)eicosanoids
E)steroids, eicosanoids, and thyroid hormone

Question 50

Which of the following chemical messengers are lipophobic?

A)peptides/proteins and steroids
B)thyroid hormones
C)steroids
D)peptides/proteins
E)amino acids

Question 51

Which of the following is the most common second messenger in the human body?

A)calcium
B)cGMP
C)DAG
D)IP3
E)cAMP

Question 52

Which type of chemical messenger is released from the axon terminal of a neuron and directly communicates with other cells?

A)paracrine
B)neurotransmitter
C)hormone
D)cytokine
E)autocrine

Question 53

What molecule, whose synthesis is catalyzed by phospholipase C, triggers the release of calcium from the endoplasmic reticulum?

A)inositol triphosphate
B)diacylglycerol
C)cGMP
D)phosphatidylinositol biphosphate
E)inositol biphosphate

Question 54

The location of receptors on a target cell depends on the solubility of the chemical messenger. Where would the receptors for lipophilic messengers be located?

A)only in the nucleus of the cell
B)on the outside of the cell
C)at a free floating ribosome
D)on the inside of the cell
E)It depends on if it is an alpha, beta, or delta type receptor.

Question 55

What protein in the blood that is relatively non- specific with respect to its ability to bind and transport chemical messengers in the blood?

A)albumin
B)protein kinase
C)corticosteroid- binding globulin
D)hemoglobin
E)cytokine

Question 56

Which type of chemical messenger, when released, binds to receptors on the cell that released the chemical messenger?

A)neurohormone
B)cytokine
C)hormone
D)neurotransmitter
E)autocrine

Question 57

Which of the following statements best describes the release of lipophobic messengers?

A)Lipophobic messengers are stored in vesicles and released by simple diffusion in response to a stimulus.
B)Lipophobic messengers are released immediately upon synthesis by simple diffusion.
C)Lipophobic messengers are stored free in the cytosol and released by simple diffusion in response to a stimulus.
D)Lipophobic messengers are stored in vesicles and released by exocytosis immediately after synthesis.
E)Lipophobic messengers are stored in vesicles and released by exocytosis in response to a stimulus.

Question 58

The enzyme that catalyzes synthesis of cAMP is called and is activated by _ .

A)phosphodiesterase : a Gi protein
B)adenylate cyclase : a Gs protein
C)phosphodiesterase : a Gs protein
D)adenylate cyclase : a Gi protein
E)phosphoprotein phosphatase : a Gi protein

Question 59

An equilibrium exists between a hormone that is bound to a carrier protein and a free hormone such that, as the amount of free hormone increases,

A)more bound hormone will be released from its carrier proteins.
B)more hormone must be synthesized to directly replace the free hormones.
C)cells will be stimulated to secrete more free hormone.
D)the amount of bound hormone will not change.
E)more free hormone will become bound to carrier proteins.

Question 60

What enzyme catalyzes synthesis of prostaglandins from arachidonic acid?

A)phospholipase C
B)phospholipase A2
C)tyrosine fi- hydroxylase
D)cyclooxygenase
E)lipoxygenase

Question 61

The number of bound receptors on a target cell depends on what two things?

A)the concentration of the messenger and the distance it has to travel
B)the concentration of the messenger and the concentration of receptors on the target cell
C)the concentration of the messenger and signal transduction
D)the type and concentration of receptors
E)the secretory cell and target cell

Question 62

What is a molecule that is similar in structure to a messenger and binds with that messenger's receptor to stimulate a similar response from the target cell?

A)protagonist
B)antagonist
C)synergist
D)agonist
E)blocker

Question 63

The affinity of a receptor for its ligand is a measure of the

A)strength of binding between ligand and receptor.
B)response produced in the target cell when the ligand binds to the receptor.
C)number of binding sites available for the ligand.
D)percent of receptors on a specific target cell with bound ligand.
E)ability of the ligand to permeate the plasma membrane and reach its receptor.

Question 64

Inflammation is characterized in part by redness and swelling. In inflammation, _ _ increases blood flow to affected tissues (producing redness)and causes fluid to leak out of the blood vessels and into the tissue (producing swelling).

A)amine
B)growth factor
C)histamine
D)clotting factor
E)pyruvic acid

Question 65

All the messengers in what class are derived from cholesterol?

A)steroids
B)amino acids
C)eicosanoids
D)peptides/proteins
E)amines

Question 66

Lipophilic hormones are transported in blood and bind to receptors located .

A)dissolved in the plasma : inside the target cell
B)inside red blood cells : inside the target cell
C)dissolved in the plasma : on the plasma membrane of the target cell
D)bound to carrier proteins : inside the target cell
E)bound to carrier proteins : on the plasma membrane of the target cell

Question 67

The a1 adrenergic receptor has the greatest affinity for what messenger?

A)dopamine
B)serotonin
C)norepinephrine
D)epinephrine
E)epinephrine and norepinephrine equally

Question 68

As the concentration of receptors on the cell membrane decreases, the response of the target cell will

A)remain the same due to saturation.
B)decrease.
C)oscillate with the concentration of the chemical messenger.
D)increase.
E)increase its affinity.

Question 69

Hormones that are dissolved in blood typically exhibit a half- life on the order of , whereas hormones that are bound to carrier proteins can remain undegraded for .

A)seconds : hours
B)seconds : minutes
C)minutes : seconds
D)hours : minutes
E)minutes : hours

Question 70

Insulin is a peptide hormone and therefore lipophobic. When insulin is released due to high blood glucose levels, the response of the cells to this hormone will be because it causes .

A)slow : a second messenger system to be activated
B)fast : enzyme- linked receptors to catalyze intracellular reactions
C)slow : amplification of proteins
D)fast : new protein synthesis
E)neutral : transcription of mRNA and translation of that mRNA into a functional protein

Question 71

Which of the following enzymes catalyzes dephosphorylation of a protein?

A)phospholipase C
B)phosphoprotein phosphatase
C)cyclooxygenase
D)dopamine fi- hydroxylase
E)phenylethanolamine N- methyl transferase

Question 72

What chemical messenger is released from endocrine glands into the bloodstream?

A)neurohormone
B)neurotransmitter
C)paracrine
D)autocrine
E)hormone

Question 73

A target cell will respond to a chemical messenger once that molecule has bound to a

A)protein kinase.
B)receptor.
C)complex in the nucleus.
D)calcium channel.
E)G protein.

Question 74

Functionally, G proteins are classified into what three types?

A)alpha, beta, and gamma
B)slow, fast, and opened or closed
C)those that affect ion channels, stimulatory G proteins, and inhibitory G proteins
D)first, second, and third messengers
E)those that affect proteins, those that affect enzymes, and those that affect specific genes

Question 75

The function of a second messenger system is to

A)keep calcium involved in these responses.
B)buffer a cell's response to a ligand.
C)isolate the response to the inside of a cell.
D)facilitate the process of covalent modification of a protein.
E)amplify the response of the first messenger.

Question 76

Cyclic AMP (cAMP)stimulates one's metabolic rate. Many supplement companies offer products claiming to increase the levels of this chemical within the body. If you had a patient on this supplement and they had high levels of cAMP in their body, what symptoms would you expect them to display?

A)hypoglycemia and low blood pressure
B)high G protein and sugar levels in their urine
C)increased heart rate and shallow breathing
D)weight gain and lethargy
E)weight loss and a high temperature

Question 77

What two systems primarily control homeostasis due to their ability to communicate over long distances?

A)nervous and cardiovascular
B)endocrine and respiratory
C)cardiovascular and respiratory
D)nervous and endocrine
E)endocrine and cardiovascular

Question 78

Doctors often prescribe baby aspirin (82 mg)to guard against the formation of blood clots instead of a higher dose of 350 mg found in a regular aspirin. Which statement best describes the distinction in dosages?

A)Aspirin causes several side effects, some good and some bad. Aspirin decreases thromboxane A2 which causes blood clots; however, at higher dosages, it also decreases the production of PGI2 (prostacyclin)that inhibits production of blood clots. Thus, higher dosages of aspirin would actually promote the formation of blood clots.
B)Low dosages of aspirin inhibit a critical enzyme in the production of prostaglandins called cyclooxygenase (COX). There are two forms of COX: 1 and 2. Low dosages enhance the production of COX- 2 which reduces blood clots. COX- 1 receptors only reduce pain.
C)Aspirin inhibits the production of PGE2 in the stomach, which protects the stomach lining from stomach acid causing ulcers. Lower dosages do not inhibit PGE2 and do not harm the stomach.
D)Both dosages actually do the same thing to prevent blood clots but 82 mg of aspirin is much cheaper than 350 mg.
E)Aspirin is an allosteric modulator that activates COX- 2 in the body and it is COX- 2 that primarily inhibits blood clot formation.

Question 79

Histamine is an example of a(n)

A)paracrine.
B)neurotransmitter.
C)autocrine.
D)hormone.
E)glial cell.

Question 80

What part of a neuron releases neurotransmitter by exocytosis?

A)soma
B)axon terminal
C)dendrites
D)axon hillock
E)All of the answers are correct.