Deck 5: Chemical Messengers

Question 1

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

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

Answer 1

E

Question 2

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

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

Answer 2

D

Question 3

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

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

Answer 3

D

Question 4

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

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

Question 5

Cells that secrete epinephrine must contain which enzymes?

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

Question 6

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

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

Question 7

Communication across a synapse is initiated by the release of a neurotransmitter from the region of the neuron.

A) axon hillock
B) axon terminal
C) dendritic
D) perisynaptic
E) postsynaptic

Question 8

All the messengers in what class are derived from cholesterol?

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

Question 9

Catecholamines are derived from what amino acid?

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

Question 10

Peptide hormones are made

A) on demand : active transport
B) on demand : simple diffusion
C) in advance : exocytosis , stored and released via .
D) in advance : receptor -mediated endocytosis
E) in advance : pinocytosis

Question 11

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

Question 12

Cells that secrete dopamine must contain which enzymes?

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

Question 13

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

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

Question 14

Thyroid hormones are synthesized from what amino acid?

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

Question 15

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 type and concentration of receptors
C) the concentration of the messenger and signal transduction
D) the secretory cell and target cell
E) the concentration of the messenger and the concentration of receptors on the target cell

Question 16

The more specific a drug is for a certain the drug and the fewer the side effects.

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

Question 17

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

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

Question 18

Vasopressin (antidiuretic hormone), which is released from the posterior pituitary, is an example of what type of chemical messenger?

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

Question 19

Histamine acts as a(n)

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

Question 20

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

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

Question 21

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

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

Question 22

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

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

Question 23

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

Question 24

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) more free hormone will become bound to carrier proteins.
D) the amount of bound hormone will not change.
E) cells will be stimulated to secrete more free hormone.

Question 25

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) Aspirin is an allosteric modulator that activates COX -2 in the body and it is COX -2 that primarily inhibits blood clot formation.
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) 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.
E) Both dosages actually do the same thing to prevent blood clots but 82 mg of aspirin is much cheaper than 350 mg.

Question 26

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

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

Question 27

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

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

Question 28

Androgens are precursor molecules for the synthesis of

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

Question 29

Lipophilic chemical messengers are poorly soluble in water. However, many of these lipophilic messengers are transported throughout the body. Their transport in blood (water) is facilitated by

A) carrier proteins.
B) lipoproteins.
C) white blood cells.
D) chylomicrons.
E) red blood cells.

Question 30

Aspirin decreases inflammation by inhibiting the actions of what enzyme?

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

Question 31

What organelle packages peptide/protein messengers into secretory vesicles?

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

Question 32

What enzyme catalyzes synthesis of prostaglandins from arachidonic acid?

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

Question 33

Once a steroid hormone is synthesized, it is

A) bound to the mitochondria until released.
B) stored in a unique protein structure that maintains steroids in the cell.
C) immediately capable of diffusing across the membrane.
D) stored in a vesicle until released.
E) bound to albumin until released from the cell.

Question 34

In order to synthesize eicosanoids, phospholipid.

A) phospholipase C : cholesterol
B) phospholipase A₂ : cholesterol _ catalyzes the release of _
_ from a membrane
C) phospholipase C : inositol biphosphate
D) phospholipase A₂ : arachidonic acid
E) phospholipase C : arachidonic acid

Question 35

Which of the following statements best describes the release of a lipophilic messenger?

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

Question 36

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

A) 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.
B) 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.
C) 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.
D) When aspirin dissolves in the interstitial fluid it causes a concentration gradient and fluid is pulled from the cell reducing inflammation.
E) The COX receptors have a greater affinity for aspirin and these speed up the reactions of healing.

Question 37

Progesterone is a potential precursor for the synthesis of

A) testosterone.
B) dehydroepiandrosterone.
C) cortisol.
D) estradiol.
E) androstenedione.

Question 38

Chronic exposure to a ligand (messenger) messenger on the target cell.

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

Question 39

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

Question 40

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

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

Question 41

Much evidence suggests that depression might be associated with deficiencies in the biogenic amines serotonin and norepinephrine. If this is true and the body has reduced concentrations of these amines, one might predict the body would

A) increase the half life
B) upregulate
C) increase the concentration of chemical messenger
D) reduce the affinity
E) downregulate

Question 42

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

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

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

Question 44

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

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

Question 45

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
)

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

Question 46

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

Question 47

What terminates the cAMP second messenger system?

A) the release of the first messenger from the receptor
B) a G protein
C) the axon terminal
D) degradation of cAMP by the liver
E) the degradation of cAMP by the enzyme cAMP phosphodiesterase

Question 48

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

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

Question 49

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

Question 50

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

Question 51

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

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

Question 52

Functionally, G proteins are classified into what three types?

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

Question 53

Typical responses to messengers require a long time to develop because they necessitate transcription of mRNA and translation of that mRNA into a functional protein.

A) lipophilic
B) lipophobic
C) protein
D) amino acid
E) peptide

Question 54

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

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

Question 55

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

Question 56

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

Question 57

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

Question 58

The function of a second messenger system is to

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

Question 59

Lipophilic hormones are transported in blood

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

Question 60

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

Question 61

The nervous system communicates via the and the endocrine system communicates via the .

A) neuron : endocrine gland
B) glial cell : hormone
C) muscle cells : specific target cells of hormones
D) synapse : bloodstream
E) electrical signals : chemical signals or paracrine cells

Question 62

The target cells of the nervous system are

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

Question 63

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

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

Question 64

Which of the following are second messengers?

A) cAMP only
B) calcium only
C) inositol triphosphate only
D) both cAMP and inositol triphosphate
E) cAMP, calcium, and inositol triphosphate

Question 65

What part of a neuron releases neurotransmitter by exocytosis?

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

Question 66

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

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

Question 67

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

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

Question 68

Which of the following enzymes catalyzes phosphorylation of a protein?

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

Question 69

Which of the following enzymes catalyzes synthesis of epinephrine from norepinephrine?

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

Question 70

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

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

Question 71

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

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

Question 72

What enzyme is activated by cAMP?

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

Question 73

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

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

Question 74

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

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

Question 75

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

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

Question 76

What chemical messenger is released by a presynaptic cell?

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

Question 77

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

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

Question 78

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

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

Question 79

The enzyme that catalyzes synthesis of cAMP is called

A) phosphodiesterase : a G_s protein
B) phosphoprotein phosphatase : a G_i protein
C) adenylate cyclase : a G_i protein
D) phosphodiesterase : a G_i protein
E) adenylate cyclase : a G_s protein

Question 80

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

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