Question 1

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

Accepted Answer

This is true. Norepinephrine and epinephrine can bind to different subtypes of adrenergic receptors (alpha or beta) which are present on different tissues throughout the body. Activation of these receptors elicits different responses depending on the subtype and location of the receptor.

Question 2

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

Accepted Answer

The sequence of events between the binding of an extracellular messenger to a receptor and the cellular responses is called a signal transduction pathway. It involves a series of biochemical steps that ultimately lead to the cellular response. Homeostatic reactions and physiological reflexes are broader terms that can include multiple pathways and systems, while a reflex arc is a specific neural pathway for reflex responses.

Question 3

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

Accepted Answer

Calcium ions are commonly used as second messengers in cellular signaling pathways. They play a crucial role in many signaling cascades, including those involved in muscle contraction, neurotransmitter release, and gene expression. Carbon monoxide and nitric oxide are both involved in cellular signaling, but they typically function as gasotransmitters rather than second messengers. Potassium ions also play important roles in cellular signaling, but they are not commonly used as second messengers.

Question 4

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

Accepted Answer

A competitive antagonist will bind to a receptor without activating it, thereby blocking the receptor from being activated by other substances. It does not initiate any cellular response or interact with effector molecules. Therefore, the correct answer is C, which states that the receptor will do nothing when a competitive antagonist binds to it.

Question 5

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

Accepted Answer

The solubility of the ligand is a significant factor because it determines whether the ligand can cross the cell membrane to interact with intracellular receptors or if it must bind to cell surface receptors.

Question 6

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

Accepted Answer

Secretion of erythropoietin represents the cellular effect of the signal transduction process, where the low oxygen signal is converted into a response by the kidney cells. This helps in the production of red blood cells to increase oxygen-carrying capacity in the blood.

Question 7

Which of the following is a second messenger? A) ATP - adenosine triphosphate B) guanylyl cyclase C) IP₃ - inositol triphosphate D) PIP₂ - Phosphatidylinositol bisphosphate

Accepted Answer

Inositol triphosphate (IP3) is a second messenger that is produced in response to extracellular signals and triggers a cascade of intracellular signaling events. Both ATP and guanylyl cyclase are involved in producing second messengers, but they are not themselves considered second messengers. Phosphatidylinositol bisphosphate (PIP2) can be cleaved to produce second messengers, but PIP₂ is not a recognized abbreviation for this molecule.

Question 8

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

Accepted Answer

Relay proteins are involved in signal transduction, which is the process of converting an extracellular signal (signaling molecule) into an intracellular response. This involves a series of relay proteins that transmit the signal downstream to ultimately cause a cellular response. Relay proteins are not directly involved in the recognition of the messenger or receptor activation, but they do play a crucial role in transducing the signal from the receptor to downstream effectors. Therefore, choice A is the best answer.

Question 9

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

Accepted Answer

Phenylephrine is an agonist of alpha-1 adrenergic receptors, similar to how epinephrine acts, but it is more selective. By stimulating these receptors, it causes vasoconstriction, which reduces swelling and congestion in the nasal passages.

Question 10

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

Accepted Answer

When there is an excess of extracellular messenger, the cell may down-regulate its receptors to prevent overstimulation. One of the mechanisms by which this occurs is through endocytosis of the receptors, which brings them inside the cell and either recycles or degrades them, ultimately reducing their availability on the cell surface. Option A (cell apoptosis) is a drastic measure and not typically used for down-regulation of receptors. Option C (initiation of translation) and option D (decreased ATP synthesis) are not directly related to receptor down-regulation in this context.

Question 11

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

Accepted Answer

Intracellular hormone receptors can be located not only in the nucleus but also in the cytoplasm. This is the incorrect statement.

Question 12

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

Accepted Answer

Lipid-soluble chemical messengers (such as steroid hormones) can easily cross the plasma membrane, and their receptors are typically located inside the cell, often in the cytosol or nucleus. These receptors can directly bind to the messenger and influence gene expression. Receptors for water-soluble messengers (such as peptide hormones) are typically located on the cell surface.

Question 13

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

Accepted Answer

The answer of Different cells respond differently to the same...

Question 14

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

Accepted Answer

Insulin acts as an extracellular messenger in the signal transduction pathway, binding to insulin receptors on the cell surface and initiating a cascade of events that lead to glucose uptake.

Question 15

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

Accepted Answer

When there are long-term high concentrations of extracellular messengers in blood, the cells can decrease the number of hormone receptors in response. This is known as receptor down-regulation. Option A, receptor up-regulation, would be the opposite effect, where the cells increase the number of receptors in response to low hormone levels. Option B, receptor saturation, refers to when all the receptors are already occupied by hormones, and additional hormone molecules cannot bind. Option C, receptor competitive inhibition, occurs when a molecule other than the hormone binds to the receptor, preventing the hormone from binding.

Question 16

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

Accepted Answer

Receptor up-regulation between the first and second dose could explain the increased effect of the drug. This means that the body has produced more receptors for the drug to act on, leading to a greater response to the same dose.

Question 17

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

Accepted Answer

Negative feedback is a common theme in physiology that involves the down-regulation and up-regulation of receptors. When a stimulus is applied, receptors are either down-regulated (decreased in number or sensitivity) or up-regulated (increased in number or sensitivity) to maintain homeostasis.

Question 18

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

Accepted Answer

Steroid hormones, such as estrogen and testosterone, are lipophilic and can easily pass through the plasma membrane of cells. Once inside the cell, they bind to intracellular receptors, which are then transported to the nucleus and directly affect gene expression. Therefore, intracellular receptors are the most likely receptors for these hormones to bind to.

Question 19

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.

Accepted Answer

All of the choices are correct. Signal transduction pathways are activated by the binding of a ligand to its receptor molecule, which then transmits the environmental signal to intracellular effector molecules. The pathway is comprised of many different types of relay molecules, which signal the response to the appropriate cellular components.

Question 20

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

Accepted Answer

The phosphorylation of intracellular proteins suggests that signal transduction is occurring, but the lack of GLUTs on the cell surface suggests a problem with the downstream action of insulin. Therefore, the problem is most likely with signal transduction, while receptor binding and activation are functioning properly.

Quiz 6: Cell Signaling

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

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

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

When a competitive antagonist binds to a receptor, the receptor

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

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?

Which of the following is a second messenger?

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

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

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

Which statement about intracellular hormone receptors is INCORRECT?

Receptors for lipid soluble chemical messengers are primarily located

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?

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?

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 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?

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

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

Signal transduction pathways