Deck 6: Cell Signaling

Question 1

Mutations in the connexin genes might DIRECTLY lead to the following problems?

A) decreased release of chemical messenger by a cell
B) uncoordinated heart beat
C) problems with binding of a chemical to a receptor
D) inability of a cell to bind to neighboring cells

Answer 1

B

Question 2

In multicellular organisms cells are

A) all tightly bound to one another
B) separated by blood
C) separated by interstitial fluid
D) connected by cytoplasmic extensions

Answer 2

C

Question 3

Extracellular chemical messengers that travel through the blood to act on distant target cells are called

A) neurotransmitters
B) hormones
C) inflammatory mediators
D) cytokines

Answer 3

B

Question 4

Endogenous extracellular molecules X and Y both bind to a receptor on the target cell. Binding of molecule X to the receptor results in changes in the cell's behavior. Binding of molecule Y does not result in changes in the cell's behavior. Which molecule can be called the ligand?

A) only molecule X
B) only molecule Y
C) neither molecule X nor Y
D) both molecules X and Y

Question 5

Which of the following is the example of cell to cell signaling?

A) creation of membrane resting potential
B) exciting a muscle fiber by motor neuron
C) propagation of action potential in the nerve fiber
D) receptor mediated endocytosis

Question 6

Which of the following steps is NOT a component of a hormone signaling cascade?

A) recognition of a hormone
B) signal transduction
C) signal translation
D) cellular response

Question 7

Which extracellular chemical messenger acts mostly locally due to its chemical instability and very short half-life?

A) nitric oxide
B) epinephrine
C) oxytocin
D) insulin

Question 8

Binding of the extracellular chemical messenger to the receptor can cause which of the following reaction(s) in the cell

A) initiation of translation
B) cell shape changes
C) activation of cellular enzymes
D) All of the choices are correct.

Question 9

In a cell to cell signaling process, signal transduction can be defined as

A) activation of the receptor
B) initiation of translation and production of new proteins
C) change of an external signal to a sequence of intracellular processes
D) adjustment of number of receptors to the strength of the signal

Question 10

Why is communication between cells so important for proper function of the multicellular organism?

A) Cells are specialized for a function and can't do everything alone.
B) Cells need to coordinate timing and intensity of organism's functions.
C) Cells are dependent on signals from other places in the body to initiate the response.
D) All of the choices are correct.

Question 11

Which of the following statements correctly describes gap junctions?

A) act as size filters, small molecules go through and large don't
B) are present only on postsynaptic membranes
C) are present only in neuronal tissues
D) their function is to increase distance between neighboring cells

Question 12

Why do some cells fail to respond to the hormonal stimulation, no matter the concentration of the hormone at those cells' membrane?

A) chemical signals are only delivered to certain tissues
B) most likely the concentration of hormone is too high
C) these cells might lack the necessary receptors
D) these cells might not have appropriate ligands

Question 13

When ligands bind to the receptors on target cells the ligands

A) provide the energy for signal transduction
B) activate a signal transduction cascade
C) change into other compounds
D) lower activation energy

Question 14

In multicellular organisms cells must communicate to make the organism work as a whole. Which of the following might be useful for both long and short distance communication between animal cells?

A) cell to cell contacts
B) secretion of molecules into body fluids
C) emitting high frequency sound waves to excite other cells
D) producing electrical impulses that flow through interstitial fluid

Question 15

Cells can send signals to other cells via

A) endocrine signaling
B) synaptic transmission
C) cell to cell binding
D) All of the choices are correct.

Question 16

Cell to cell adhesion is an important method of cell to cell communication

A) when sending information over long distances
B) during development and organ formation in the fetus
C) for rapid communication between two organs in the body
D) for integrating electrical potentials of neighboring cells

Question 17

What is the most common method of communication between cells in animal bodies?

A) secreting chemical messengers that attach to target cells
B) use of direct connections between the cytoplasm of neighboring cells
C) use of ions to create current flow through the interstitial fluid
D) producing cell extensions that reach to other cells in order to temporarily touch them and pass the message

Question 18

An intercellular junction that allows for direct passage of ions between two neighboring cells is called

A) tight junction
B) receptor junction
C) gap junction
D) desmosome

Question 19

When parathyroid glands sense low blood Ca²⁺ levels they secrete an extracellular chemical messenger that disperses all over the body through the blood in order to trigger a series of events that move Ca²⁺ levels back towards normal. This process is an example of

A) endocrine signaling
B) synaptic signaling
C) local signaling
D) exocrine signaling

Question 20

Which type of signaling involves chemical messengers working on other cells in the immediate neighborhood of secretory cell?

A) endocrine
B) paracrine
C) autocrine
D) exocrine

Question 21

Ligands that mimic the natural biological response when they bind to a receptor are known as

A) antagonists
B) allosteric modulators
C) agonists
D) agglutinins

Question 22

Recognizing and binding extracellular messengers is the function of

A) linkers
B) transporters
C) receptors
D) enzymes

Question 23

During the reanimation procedure in the ER doctors gave a patient an injection of epinephrine to increase his heart rate and blood pressure. The heart rate and blood pressure went up but not enough. The second dose of the same drug seemed not to have an effect. What is a possible explanation for this result?

A) the receptors reached the saturation level with the drug between the first and second dose
B) the activation energy of the receptors went down between the first and second dose
C) the receptors changed their transduction pathway between the first and second dose
D) the cell expressed more receptors between the first and second dose

Question 24

The gas, nitric oxide (NO), is an extracellular signaling molecule travels through interstitial fluid to reach target cells such as smooth muscle. NO acts here as a/an

A) neurotransmitter
B) local mediator
C) hormone
D) enzyme

Question 25

As a rule, lipid soluble hormones require a transport protein to circulate in the bloodstream. What is the function of the transport protein?

A) it decreases hormone solubility in blood plasma
B) it helps the hormone to cross cell membranes and enter the target cells
C) it is required for binding of a hormone to its receptor
D) it increases the ability of hormones to move through blood

Question 26

The ligands that bind to a receptor, but keep the cell from responding are known as

A) agonists
B) activators
C) antagonists
D) potentiators

Question 27

Which of the following is true about receptors?

A) all receptors are located on the plasma membrane
B) receptors bind only soluble signal molecules
C) receptors form covalent bonds with their ligands
D) all receptors are proteins

Question 28

Glucagon is a peptide hormone. Based on general characteristics of peptide hormones what is true about growth hormone?

A) it needs the help of transport protein to reach its target cells
B) it binds to specific receptor and activates a signal transduction cascade
C) it diffuses into the cell when it reaches its target
D) it is a hydrophobic molecule that is degraded in watery blood

Question 29

The drugs called beta blockers are competitive antagonists often used in medicine to prevent epinephrine from binding to beta adrenergic receptors, and in turn leading to decrease of blood pressure and heart rate. When beta blockers are used in the patient they change

A) receptors' affinity for epinephrine
B) receptors' specificity for epinephrine
C) number of receptors bound to epinephrine
D) adrenergic receptor saturation

Question 30

Neurotransmitters and neurohormones both

A) have an effect only on neuronal target cells
B) affect only cells that have specific receptors
C) travel in blood to their target cells
D) convert chemical signal to electricity

Question 31

Which of the following statements best characterizes the hormone-receptor interactions?

A) receptors can have different affinities for multiple ligands
B) each hormones will only interact with one type of receptor
C) most cells express receptors for all hormone
D) the hormone-receptor contact is generally irreversible

Question 32

Glucagon is a peptide hormone released by the pancreas that increases blood glucose levels. Which statement correctly describes signaling by glucagon?

A) Glucagon initiates the cascade of glycogen synthesis in all cells.
B) Glucagon causes glycogen breakdown only in cells that express the glucagon receptor.
C) Glucagon travels in blood bound to a transport protein.
D) Glucagon stimulation of liver glucose synthesis is an example of paracrine signaling.

Question 33

The property of receptors that limits them to binding only molecules of certain shape is called

A) competition
B) saturation
C) affinity
D) specificity

Question 34

During an asthma attack, cells called mast cells that lie just under the mucosal membrane of the airways release histamine, which in turn leads to inflammation of the mucosal membrane. Which type of signaling does this represent?

A) autocrine
B) paracrine
C) endocrine
D) exocrine

Question 35

The most significant difference between paracrine and autocrine signaling is the

A) type of cell that releases the signaling molecule
B) target cell that responds to the signaling molecule
C) method the signaling molecule is transported
D) nature of the intracellular transduction pathway

Question 36

What are the effects of the release of locally acting chemical signaling messengers known as prostaglandins?

A) tissue inflammation and fever
B) localized contraction of smooth muscle
C) intensifying the sensation of pain
D) All of the choices are correct.

Question 37

Cytokines secreted by cancer cells that increase cancer growth are an example of which type of signaling?

A) autocrine
B) endocrine
C) exocrine
D) merocrine

Question 38

Receptor antagonists are often used as drugs to block the response caused by an internal natural ligand. What property of receptors could these drugs rely on?

A) saturation
B) competitive binding
C) receptor location
D) up-regulation

Question 39

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

A) inhibit prostaglandin synthesis
B) promote prostaglandin synthesis
C) promote synthesis of leukotrienes
D) promote activities associated with cell division and wound healing

Question 40

The strength of the cell's response to hormonal stimulation is determined by

A) concentration of the hormone in blood
B) the type of cell releasing the hormone
C) the chemical classification of the hormone
D) All of the choices are correct.

Question 41

Norepinephrine and epinephrine can trigger different responses in different locations depending upon which type of adrenergic receptor is present on those tissues.

Question 42

The sequence of events between the binding of an extracellular messenger to a receptor and the cellular responses is called a

A) homeostatic reaction
B) physiological reflex
C) reflex arc
D) signal transduction pathway

Question 43

Which of the following inorganic molecules is used by cells as a second messenger?

A) calcium ions
B) carbon monoxide
C) nitric oxide
D) potassium ions

Question 44

When a competitive antagonist binds to a receptor, the receptor

A) starts the signal transduction pathway
B) initiates production of intermediates that in turn affect cell activity
C) will do nothing
D) directly interacts with cell effector molecules

Question 45

What are the most significant factors that determine cellular localization of a receptor?

A) the solubility of the ligand
B) the size of the ligand
C) the size of the receptor molecule
D) the distance traveled by the ligand from its source

Question 46

When kidney cells sense low levels of oxygen in blood they secrete erythropoietin. In this particular signaling pathway (response to low oxygen), secretion of erythropoietin represents which step of the signal transduction process?

A) recognition of the signal
B) signal transduction
C) relay molecules
D) cellular effect

Question 47

Which of the following is a second messenger?

A) ATP - adenosine triphosphate
B) guanylyl cyclase
C) IP₃ - inositol triphosphate
D) PIP₂ - Phosphatidylinositol bisphosphate

Question 48

In the process leading from a signaling molecule to a cellular response, relay proteins are involved in

A) signal transduction
B) recognition of the messenger
C) receptor activation
D) cellular response

Question 49

Phenylephrine reduces secretion of mucus and causes blood vessel constriction, and therefore alleviates nasal congestion because it

A) is an agonist of epinephrine
B) is an antagonist of epinephrine
C) competes with epinephrine
D) it is a blocker of the receptor

Question 50

What is the cellular mechanism of receptor down-regulation in response to an excess of extracellular messenger?

A) cell apoptosis
B) endocytosis of receptors
C) initiation of translation
D) decreased ATP synthesis

Question 51

Which statement about intracellular hormone receptors is INCORRECT?

A) have affinity for lipid soluble messengers
B) can be located within target cell nuclei
C) are only found in the nucleus
D) are activated when they bind to their ligands

Question 52

Receptors for lipid soluble chemical messengers are primarily located

A) on the cell surface
B) inside the cell
C) in secretory vesicles
D) in endosomes

Question 53

Different cells respond differently to the same messengers. For example, epinephrine binding activates glycogenolysis in skeletal muscle but increases of strength of contraction in the heart. What must be true in order to explain this difference?

A) the cells must have different types of adrenergic receptors
B) the cells' receptors must have different affinities for epinephrine
C) the cells must express different sets of effector proteins
D) the cells' receptors must have different saturation points for epinephrine

Question 54

In skeletal muscle fibers, exposure to insulin leads to an increase in glucose uptake from blood. In this process, insulin works as what component of signal transduction pathway?

A) extracellular messenger
B) receptor
C) second messenger
D) cellular effector

Question 55

The decreased number of hormone receptors in the cells in response to long-term high concentrations of the extracellular messengers in blood is called

A) receptor up-regulation
B) receptor saturation
C) receptor competitive inhibition
D) receptor down-regulation

Question 56

A person takes a drug and notices an effect. The next time they the same dose of that drug, they notice a much larger effect. Which of the following could explain this?

A) receptor saturation on the second dose but not the first
B) receptor up-regulation between the first and second dose
C) receptor down-regulation between the first and second dose
D) a stronger affinity for the drug during the first dose

Question 57

Down-regulation and up-regulation of the receptors are both examples of a common theme in physiology known as

A) the law of mass balance
B) tonic control
C) energy conversion
D) negative feedback

Question 58

Estrogen and testosterone are steroid hormones, and are most likely to bind to

A) plasma membrane receptors
B) G protein coupled receptors
C) ion channel receptors
D) intracellular receptors

Question 59

Signal transduction pathways

A) are activated by binding a ligand to its receptor molecules
B) transmit the environmental signal to intracellular effector molecules
C) are comprised of many different types of relay molecules
D) All of the choices are correct.

Question 60

The insulin signaling pathways involves binding of insulin to its receptor, leading to the eventual insertion of glucose transport proteins (GLUTs) into the cell membrane. In a cell that does not respond properly to insulin, scientists find that following exposure to insulin various intracellular proteins are phosphorylated, but there is no increase in the amount of GLUTs on the cell surface. The most likely explanation for this is that

A) signal transduction is working, but there is a problem with receptor binding and activation
B) receptor binding and activation and signal transduction are both working
C) receptor binding and activation is working, but there is a problem with signal transduction
D) receptor binding and activation and signal transduction are both not working

Question 61

Which of the following would NOT be a good property for a second messenger?

A) localized in the cytosol
B) long lived and stable
C) fast acting
D) small and soluble

Question 62

Cortisol is a steroid hormone involved in the stress response. What is the mechanism of cortisol action in the cells?

A) releases Ca²⁺ from endoplasmic reticulum
B) alters gene expression
C) causes production of second messengers
D) activates phosphorylation of cellular effector molecules

Question 63

Myosin light chain kinase is phosphorylated in smooth muscle cells in response to nitric oxide signaling resulting in

A) smooth muscle relaxation and blood vessel dilation
B) smooth muscle contraction and blood vessel dilation
C) smooth muscle relaxation and blood vessel constriction
D) smooth muscle contraction and blood vessel constriction

Question 64

Calcitriol, popularly known as the active form of vitamin D, is a hydrophobic hormone. Which of the following is most likely to be a correct statement about calcitrol signaling?

A) Calcitriol binds to a transporter to cross the membrane.
B) Calcitriol binds to plasma membrane receptors.
C) Calcitriol forms hormone-receptor complexes in the cytoplasm.
D) Calcitriol exerts its effects by stimulating an intracellular second messenger system.

Question 65

Steroid hormones

A) bind to G protein coupled receptors
B) form hormone-receptor complexes in the cytoplasm or nucleus
C) generally exert their effects by stimulating an intracellular second messenger system
D) bind to a transporter to cross the membrane

Question 66

Which of the following is a difference between receptor tyrosine kinases and G protein coupled receptors?

A) Dimerization of the receptor is necessary for tyrosine kinase receptors but not G protein coupled receptors.
B) Receptor tyrosine kinases are the main type of receptors for interleukins, while G protein coupled receptors are the main type of receptors for steroids.
C) Tyrosine kinase domains are located extracellularly, while G protein coupled receptors are located intracellularly.
D) Receptor tyrosine kinases produce the second messenger cAMP, while G protein coupled receptors do not.

Question 67

Atrial natriuretic peptide

A) promotes the reabsorption of calcium from primary filtrate
B) contributes to the reabsorption of water and sodium from urine in kidneys
C) promotes excretion of sodium and water into urine
D) dilates atria to accommodate the extra blood volume

Question 68

Where in the cell might you find thyroid receptors?

A) in the nucleus bound to DNA
B) on the outside of plasma membrane
C) both on the plasma membrane and in the cytosol
D) only thyroid cells have thyroid receptors

Question 69

Erectile dysfunction is remedied by the drug known as Viagra (sildenafil) because it

A) inhibits the activity of cGMP phosphodiesterase
B) produces elevated cGMP levels in penile vascular smooth muscle
C) prolongs presence of blood in the penis
D) All of the choices are correct.

Question 70

Which of the following is NOT a common intracellular second messenger?

A) 1,2-diacylglycerol (DAG)
B) inositol 1,4,5-trisphosphate (IP₃)
C) adenosine triphosphate (ATP)
D) 3', 5' - cyclic GMP (cGMP)

Question 71

Atrial natriuretic peptide receptor is a

A) cytoplasmic form of guanylyl cyclase
B) plasma membrane form of guanylyl cyclase
C) causes production of second messenger cAMP
D) stimulates hydrolysis of ATP

Question 72

cGMP is a second messenger in the nitric oxide signaling pathway. What enzyme is responsible for production of cGMP?

A) adenylyl cyclase
B) guanylyl cyclase
C) phosphodiesterase
D) protein kinase G

Question 73

Which of the following receptors cross-phosphorylate after dimerization?

A) G protein coupled receptors
B) ion channel receptors
C) receptors tyrosine kinases
D) cytokine receptors

Question 74

Most of the growth factors bind to

A) G protein coupled receptors
B) receptor tyrosine kinases
C) receptor threonine kinases
D) ion channel receptors

Question 75

A person has bad case of poison ivy and his doctors decide to give him a "cortisol" injection. What type of receptor is responsible for the cortisol actions leading to the relief of symptoms of poison ivy allergy?

A) G protein coupled receptor
B) receptor tyrosine kinase
C) intracellular receptor
D) ion channel receptor

Question 76

Receptor tyrosine kinases

A) are located in the nucleus or cytoplasm
B) have an intracellular kinase domain
C) are involved in lipid soluble hormone detection
D) contain a G-protein binding loop

Question 77

Binding of nerve growth factor to a receptor tyrosine kinase causes all of the following except

A) dimerization of the receptor
B) hydrolysis of GTP on a G protein
C) cross-phosphorylation of the receptor
D) interaction of the receptor with the relay proteins

Question 78

Choose the correct statement concerning second messengers.

A) Lipid derived second messengers are produced by enzymes called cyclases.
B) cAMP is a second messenger made by receptor tyrosine kinases.
C) PIP₃ induces the release of Ca²⁺ from the intracellular stores.
D) DAG and IP₃ are derived from the membrane phospholipid PIP₂.

Question 79

Acetylcholine is a neurotransmitter that binds to ion channel receptors. What statement correctly characterizes this type of receptor?

A) it is at the same time a receptor and an ion channel
B) it is an intracellular receptor
C) it activates second messenger production
D) its signal transduction pathway has many relay molecules

Question 80

Aldosterone is a steroid hormone that regulates the balance of ions in the body by increasing transcription and insertion of Na⁺ channels in kidney epithelial cells. Which statements are correct about the signal transduction pathway aldosterone initiates in kidney epithelium?

A) aldosterone binds to plasma membrane receptors
B) occupied aldosterone receptors directly bind to DNA
C) second messengers activate protein kinases and phosphorylation
D) relay molecules pass the signal from receptor to the nucleus