Question 1

_____ is formed from the amino acid L-______ in a reaction catalyzed by the enzyme _____.

Accepted Answer

Nitric oxide is formed from the amino acid L-arginine in a reaction catalyzed by the enzyme nitric oxide synthase.

Question 2

The activation of a common effector by signals from a variety of unrelated receptors, each of which binds to its own ligand, is called _________.

Accepted Answer

Convergence refers to the process where multiple signaling pathways activate a common downstream effector, integrating signals from various sources to produce a unified response.

Question 3

Why does calcium not bind to calmodulin in a non-stimulated cell?

Accepted Answer

Calmodulin's affinity for calcium ions is regulated by the intracellular calcium concentration. In a non-stimulated cell, the intracellular calcium concentration is low, and therefore, the affinity of calmodulin for calcium ions is also low. As a result, calcium does not bind to calmodulin in a non-stimulated cell.

Question 4

In which organism below has calmodulin not been found?

Accepted Answer

Calmodulin has not been found in bacteria. It is a protein found in plants, animals, yeasts, and humans.

Question 5

Which inorganic gas has been shown to act as a second messenger that relaxes the smooth muscles of blood vessels?

Accepted Answer

Nitric oxide (NO) has been shown to act as a second messenger that relaxes the smooth muscles of blood vessels.

Question 6

The passage of signals back and forth between different pathways is referred to as _________.

Accepted Answer

The passage of signals back and forth between different pathways is referred to as cross-talk.

Question 7

A family of proteins homologous to the products of the CED-3 gene in C. elegans has been discovered in mammals. What is this family of proteins called?

Accepted Answer

The family of proteins homologous to the products of the CED-3 gene in C. elegans in mammals is called caspases.

Question 8

How were nitroglycerine's therapeutic benefits discovered?

Accepted Answer

Nitroglycerine's therapeutic benefits were accidentally discovered when dynamite factory workers with heart conditions experienced less angina on days that they worked with nitroglycerine-based explosives.

Question 9

How does the immune system manage to avoid recognizing and attacking normal cells within the body?

Accepted Answer

T lymphocytes that have the ability to recognize normal cells within the body are eliminated by apoptosis early in the development of the immune system. This process is called negative selection, and it helps to prevent autoimmune reactions in which the immune system attacks the body's own tissues. However, it is important to note that there are some cases where the immune system can mistakenly attack normal cells, leading to autoimmune diseases like lupus or rheumatoid arthritis.

Question 10

Why did the smooth muscle in cultured strips of aorta not respond to acetylcholine by relaxing, while the smooth muscle of aortic rings did?

Accepted Answer

The endothelial layer in aortic strips had been rubbed away during dissection, while in aortic rings it remained intact. This layer is necessary for the production of nitric oxide, which causes relaxation of the smooth muscle cells. Without this production, the smooth muscle cells cannot relax, even in the presence of acetylcholine.

Question 11

How does Viagra enhance erectile function of the penis?

Accepted Answer

Viagra (sildenafil) works by inhibiting the enzyme phosphodiesterase type 5 (PDE-5), which is responsible for breaking down cyclic guanosine monophosphate (cGMP). By inhibiting PDE-5, Viagra increases the levels of cGMP in the smooth muscle of the penis, leading to relaxation and increased blood flow, which results in improved erectile function. Option A, B, and C are incorrect because they inhibit the production and release of cGMP, which is the opposite of what Viagra does. Option E is also incorrect as it is not involved in the pathway of Viagra's mechanism of action.

Question 12

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentration?

Accepted Answer

The calcium-binding protein that acts in conjunction with calcium ion to bring about cytoplasmic responses is known as calmodulin. Calpactin is not involved in cytoplasmic calcium regulation, while calcariain and callistin are not known calcium-binding proteins. Modulocalcin is not a recognized term.

Question 13

What agent made by endothelial cells makes blood vessel smooth muscle cells relax?

Accepted Answer

Nitric oxide (NO) is the agent made by endothelial cells that causes blood vessel smooth muscle cells to relax. NO acts as a vasodilator, signaling to the adjacent smooth muscle cells to relax and widen the blood vessel, allowing for increased blood flow. Acetylcholine and cAMP are involved in other signaling pathways and do not directly cause smooth muscle relaxation. cGMP can contribute to smooth muscle relaxation but it is not the primary agent made by endothelial cells.

Question 14

Which gene in C. elegans was found to play a critical role in apoptosis?

Accepted Answer

CED-3, also known as the cell death protein-3, is a key regulator of programmed cell death or apoptosis in C. elegans. It functions as a caspase-like cysteine protease that is activated in response to apoptotic signals and triggers a cascade of events leading to cell death. Mutations in the ced-3 gene have been shown to block the apoptotic process in C. elegans, resulting in the accumulation of excess cells and abnormal development.

Question 15

What molecule is responsible for activating Rsk-2?

Accepted Answer

Rsk-2 is a member of the MAP kinase family, and it is activated by MAPK through phosphorylation. Therefore, the correct answer is D, MAPK.

Question 16

Orai1 is a tetrameric _______ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca²⁺ stores in ________.

Accepted Answer

Orai1 is a calcium ion channel involved in store-operated calcium entry, crucial for T lymphocyte function. Deficiency in Orai1 affects calcium signaling in T cells, leading to immune deficiencies.

Question 17

In which of the following biological processes is nitric oxide not involved?

Accepted Answer

Nitric oxide is not involved in the process of hearing. It plays roles in anticoagulation, neurotransmission, smooth muscle relaxation, and visual perception.

Question 18

What stimulus triggered by the binding of acetylcholine then activates nitric oxide synthase?

Accepted Answer

The binding of acetylcholine triggers the opening of ion channels, causing a rise in cytoplasmic Ca2+ concentration. This rise in Ca2+ concentration then activates nitric oxide synthase.

Question 19

To which amino acid is nitric oxide added, altering the activity, turnover and/or interactions of proteins like hemoglobin, Ras, ryanodine channels and caspases?

Accepted Answer

Nitric oxide is added to the amino acid cysteine, resulting in S-nitrosylation, which can alter the activity, turnover, and/or interactions of proteins.

Question 20

How is caspase-activated DNase (CAD)activated?

Accepted Answer

CAD is a nuclease that is activated by cleavage of its inhibitor ICAD by caspases. This cleavage leads to the release of the active CAD enzyme, which is then able to cleave chromosomal DNA during apoptosis.

Quiz 15: Cell Signaling and Signal Transduction: Communication Between Cells

_ is formed from the amino acid L- in a reaction catalyzed by the enzyme ___.

The activation of a common effector by signals from a variety of unrelated receptors, each of which binds to its own ligand, is called _________.

Why does calcium not bind to calmodulin in a non-stimulated cell?

In which organism below has calmodulin not been found?

Which inorganic gas has been shown to act as a second messenger that relaxes the smooth muscles of blood vessels?

The passage of signals back and forth between different pathways is referred to as _________.

A family of proteins homologous to the products of the CED-3 gene in C. elegans has been discovered in mammals. What is this family of proteins called?

How were nitroglycerine's therapeutic benefits discovered?

How does the immune system manage to avoid recognizing and attacking normal cells within the body?

Why did the smooth muscle in cultured strips of aorta not respond to acetylcholine by relaxing, while the smooth muscle of aortic rings did?

How does Viagra enhance erectile function of the penis?

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentration?

What agent made by endothelial cells makes blood vessel smooth muscle cells relax?

Which gene in C. elegans was found to play a critical role in apoptosis?

What molecule is responsible for activating Rsk-2?

Orai1 is a tetrameric _ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca²⁺ stores in __.

In which of the following biological processes is nitric oxide not involved?

What stimulus triggered by the binding of acetylcholine then activates nitric oxide synthase?

To which amino acid is nitric oxide added, altering the activity, turnover and/or interactions of proteins like hemoglobin, Ras, ryanodine channels and caspases?

How is caspase-activated DNase (CAD) activated?

Quiz 15: Cell Signaling and Signal Transduction: Communication Between Cells

_____ is formed from the amino acid L-______ in a reaction catalyzed by the enzyme _____.

The activation of a common effector by signals from a variety of unrelated receptors, each of which binds to its own ligand, is called _________.

Why does calcium not bind to calmodulin in a non-stimulated cell?

In which organism below has calmodulin not been found?

Which inorganic gas has been shown to act as a second messenger that relaxes the smooth muscles of blood vessels?

The passage of signals back and forth between different pathways is referred to as _________.

A family of proteins homologous to the products of the CED-3 gene in C. elegans has been discovered in mammals. What is this family of proteins called?

How were nitroglycerine's therapeutic benefits discovered?

How does the immune system manage to avoid recognizing and attacking normal cells within the body?

Why did the smooth muscle in cultured strips of aorta not respond to acetylcholine by relaxing, while the smooth muscle of aortic rings did?

How does Viagra enhance erectile function of the penis?

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentration?

What agent made by endothelial cells makes blood vessel smooth muscle cells relax?

Which gene in C. elegans was found to play a critical role in apoptosis?

What molecule is responsible for activating Rsk-2?

Orai1 is a tetrameric _______ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca2+ stores in ________.

In which of the following biological processes is nitric oxide not involved?

What stimulus triggered by the binding of acetylcholine then activates nitric oxide synthase?

To which amino acid is nitric oxide added, altering the activity, turnover and/or interactions of proteins like hemoglobin, Ras, ryanodine channels and caspases?

How is caspase-activated DNase (CAD) activated?

_ is formed from the amino acid L- in a reaction catalyzed by the enzyme ___.

Orai1 is a tetrameric _ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca²⁺ stores in __.