Mini 1 Part 2 Cell Signaling

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1. Many cytoplasmic enzymes become activated in response to an elevated calcium concentration.  In most cases these effects are mediated by the protein

Explanation

Calmodulin is a protein that plays a crucial role in regulating various cellular processes in response to changes in calcium concentration. When calcium levels rise, calmodulin binds to calcium ions and undergoes a conformational change, allowing it to activate or modulate the activity of target enzymes. This activation of cytoplasmic enzymes by calmodulin helps to regulate processes such as muscle contraction, cell signaling, and gene expression. Therefore, the correct answer is calmodulin.

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About This Quiz
Cell Signaling Quizzes & Trivia

Mini 1 part 2 Cell Signaling quiz assesses knowledge on mechanisms like cAMP, IP3, and their roles in cellular processes. It covers topics such as hormone effects, gene... see moretranscription, and receptor differences, essential for students and professionals in biological sciences. see less

2. Many cytoplasmic enzymes become activated in response to an elevated calcium concentration.  In most cases these effects are mediated by the protein:

Explanation

Calmodulin is a protein that plays a crucial role in regulating the activity of many cytoplasmic enzymes in response to an elevated calcium concentration. It acts as a calcium-binding protein and undergoes a conformational change when it binds to calcium ions. This conformational change allows calmodulin to interact with and activate various enzymes, such as protein kinases, phosphatases, and phosphodiesterases. By binding to calmodulin, these enzymes are able to carry out their specific functions in response to changes in intracellular calcium levels. Therefore, calmodulin serves as a key mediator in the activation of cytoplasmic enzymes in the presence of elevated calcium.

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3. The actions of insulin are initiated by:

Explanation

Insulin initiates its actions by phosphorylating the insulin receptor on tyrosine side chains. This phosphorylation activates the receptor, leading to a cascade of intracellular signaling events that regulate glucose uptake, glycogen synthesis, and protein synthesis. Phosphorylation of the insulin receptor on tyrosine side chains is a critical step in insulin signaling and is necessary for the downstream effects of insulin on cellular metabolism and growth.

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4. Some hormones act by triggering the release of calcium from the endoplasmic reticulum. These hormones can regulate gene expression, usually by:

Explanation

Some hormones trigger the release of calcium from the endoplasmic reticulum, which then activates calmodulin-regulated protein kinases. These protein kinases phosphorylate nuclear transcription factors, which in turn regulate gene expression by binding to promoters and enhancers of genes. This process allows for the control of gene expression in response to hormonal signals.

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5. Inositol 1,4,5-trisphosphate (IP3) is a second messenger of many hormones. To form this second messenger, you need the enzyme:

Explanation

Phospholipase C is the correct answer because it is the enzyme responsible for cleaving phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 then acts as a second messenger by binding to IP3 receptors on the endoplasmic reticulum, leading to the release of calcium ions into the cytoplasm. This calcium release triggers various cellular responses, including hormone secretion, muscle contraction, and gene expression. Therefore, without the action of phospholipase C, the formation of IP3, and subsequent cellular responses mediated by IP3, would not occur.

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6. A patient is found to have a small benign tumor in the thyroid gland that overproduces thyroid hormones. The somatic mutation that is most likely to cause this tumor is one that

Explanation

The correct answer is "prevents hydrolysis of bound GTP by the Gs protein." This mutation would lead to a constitutively active Gs protein, which would result in continuous activation of adenylyl cyclase and increased production of cyclic AMP (cAMP). Increased cAMP levels would then stimulate the thyroid gland to overproduce thyroid hormones.

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7. CAMP stimulates hormone production and cell proliferation in many endocrine tissues including the thyroid gland. Therefore a type of somatic mutation that is most likely to lead to the formation of a hormone-overproducing benign tumor in the thyroid gland (a "toxic nodule") is one that causes:

Explanation

The Gs protein is responsible for activating adenylate cyclase, which in turn increases the production of cAMP. If the Gs protein is unable to hydrolyze its bound GTP, it will remain in its active state, continuously stimulating adenylate cyclase and leading to excessive production of cAMP. This excessive cAMP production can stimulate hormone production and cell proliferation in the thyroid gland, ultimately resulting in the formation of a hormone-overproducing benign tumor. Therefore, the inability of the Gs protein to hydrolyze its bound GTP is the most likely somatic mutation to cause the formation of a toxic nodule in the thyroid gland.

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8. A linkage study has found that there is a gene for test taking skill in a particular region on the long arm of chromosome 4. A search of the human genome sequence shows that this chromosomal region contains a gene of unknown function. This gene encodes a protein that has not only a signal sequence, but also seven hydrophobic sequences, each about 20 amino acid residues long. The gene product is most likely:

Explanation

The correct answer is a hormone receptor that is linked to G-proteins. This is because the gene in question encodes a protein with a signal sequence, suggesting that it is secreted from the cell. Additionally, the presence of hydrophobic sequences indicates that the protein is likely embedded in the cell membrane. Hormone receptors are often embedded in the cell membrane and are linked to G-proteins, which are involved in signal transduction pathways. Therefore, it is likely that the gene product in this case is a hormone receptor that is linked to G-proteins.

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9. One important feature of the insulin receptor is:

Explanation

The insulin receptor is known for its ability to phosphorylate proteins on tyrosine side chains. This phosphorylation process plays a crucial role in insulin signaling and helps regulate various cellular processes such as glucose uptake, glycogen synthesis, and protein synthesis. By phosphorylating specific proteins, the insulin receptor initiates a cascade of signaling events that ultimately result in the cellular responses to insulin.

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10. The second messenger cAMP induces its effects by binding to the regulatory subunits of protein kinase A. What is the immediate target of the second messenger IP3?

Explanation

The immediate target of the second messenger IP3 is a calcium channel in the ER membrane. IP3 binds to specific receptors on the ER membrane, causing the release of calcium ions from the ER into the cytoplasm. This increase in cytoplasmic calcium levels then triggers various cellular responses, such as muscle contraction, secretion, and gene expression. Therefore, the correct answer is a calcium channel in the ER membrane.

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11. What is the difference between nicotinic and muscarinic acetylcholine receptors?

Explanation

Nicotinic acetylcholine receptors are ion channels, meaning they allow the flow of ions across the cell membrane when activated by acetylcholine. On the other hand, muscarinic acetylcholine receptors are coupled to G-proteins, which means they initiate intracellular signaling pathways when activated by acetylcholine. Therefore, the correct answer states that nicotinic receptors are ion channels, while muscarinic receptors are coupled to G-proteins.

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12. There is much overlap of the intracellular signaling cascades of growth factors such as EGF (epidermal growth factor) and PDGF (platelet-derived growth factor) with those triggered by:

Explanation

Insulin is known to activate several intracellular signaling pathways, including the PI3K/Akt pathway and the MAPK pathway. These pathways are also activated by growth factors like EGF and PDGF. Therefore, there is significant overlap in the intracellular signaling cascades triggered by insulin and these growth factors.

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13. Growth factors and insulin can regulate gene expression. Which mechanism is most likely to contribute to this effect?

Explanation

MAP kinases are a family of protein kinases that are involved in various cellular processes, including gene expression. Phosphorylation of transcription factors by MAP kinases can regulate their activity and ability to bind to DNA, thereby influencing gene expression. This phosphorylation event can be triggered by growth factors and insulin, which can activate the MAP kinase signaling pathway. Therefore, the phosphorylation of transcription factors by MAP kinases is the most likely mechanism to contribute to the regulation of gene expression by growth factors and insulin.

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14. You work as research director for a pharmaceutical company. One of your tasks is the development of new anti-hypertensive (blood pressure lowering) drugs. Of the following, the most promising drug would be one that:

Explanation

Preventing the degradation of cAMP in vascular smooth muscle cells would lead to an increase in the levels of cAMP, which would result in relaxation of the smooth muscles in blood vessels. This would ultimately lead to vasodilation and a decrease in blood pressure. By specifically targeting vascular smooth muscle cells and not other cells in the body, the drug would have a more targeted effect on blood pressure regulation.

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15. Glucagon can induce gene transcription in the liver.  How?

Explanation

Glucagon activates the protein kinase A (PKA) pathway, which leads to the phosphorylation of nuclear transcription factors. This phosphorylation allows the transcription factors to bind to specific regulatory sequences in the genes' regulatory regions, thereby inducing gene transcription in the liver.

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Many cytoplasmic enzymes become activated in response to an elevated...
Many cytoplasmic enzymes become activated in response to an elevated...
The actions of insulin are initiated by:
Some hormones act by triggering the release of calcium from the...
Inositol 1,4,5-trisphosphate (IP3) is a second messenger of many...
A patient is found to have a small benign tumor in the thyroid gland...
CAMP stimulates hormone production and cell proliferation in many...
A linkage study has found that there is a gene for test taking skill...
One important feature of the insulin receptor is:
The second messenger cAMP induces its effects by binding to the...
What is the difference between nicotinic and muscarinic acetylcholine...
There is much overlap of the intracellular signaling cascades of...
Growth factors and insulin can regulate gene expression. Which...
You work as research director for a pharmaceutical company. One of...
Glucagon can induce gene transcription in the liver.  How?
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