Cell Signaling and Transduction Quiz

Adenylyl cyclase is the correct answer because it is an enzyme that catalyzes the conversion of ATP (adenosine triphosphate) to cAMP (cyclic adenosine monophosphate). This conversion is an important step in many cellular signaling pathways, as cAMP acts as a second messenger to transmit signals within cells. Adenylyl cyclase is responsible for regulating the levels of cAMP in the cell, which in turn regulates various cellular processes such as metabolism, gene expression, and cell growth.

IP3 is a signaling molecule that binds to receptors on the endoplasmic reticulum (ER) membrane. When IP3 binds to these receptors, it triggers the release of calcium ions (Ca2+) from the ER into the cytoplasm. This release of Ca2+ is an important cellular signaling event that regulates various cellular processes such as muscle contraction, cell division, and neurotransmitter release. Therefore, the statement that IP3 causes the release of Ca2+ in the endoplasmic reticulum into the cytoplasm is true.

Diacylglycerol (DAG) is known to activate protein kinase C (PKC), a type of enzyme that plays a crucial role in various cellular processes. When DAG activates PKC, it triggers a cascade of events that ultimately leads to a physiological effect. Therefore, the statement is true.

CREB is indeed a cAMP response element-binding protein that functions as a transcription factor. It binds to specific DNA sequences known as cAMP response elements (CRE) and regulates the transcription of downstream genes. This means that CREB can either increase or decrease the expression of genes based on its binding to CREs. Therefore, the statement "CREB is a cAMP response element-binding protein that binds to certain DNA sequences called cAMP response elements (CRE), thereby increasing or decreasing the transcription of the downstream genes" is correct.

The NO/cGMP pathway is known to activate protein kinase G (PKG), which in turn produces physiological effects. This means that when this pathway is activated, it leads to the activation of PKG, which then produces certain physiological effects in the body. Therefore, the statement that the NO/cGMP pathway results in the activation of PKG and produces physiological effects is true.

Soluble guanylyl cyclase (sGC) is indeed a nitric oxide (NO) receptor that synthesizes cGMP. When NO binds to sGC, it activates the enzyme, leading to the conversion of GTP to cGMP. This signaling pathway is important in various physiological processes, including smooth muscle relaxation, platelet aggregation, and neurotransmission. Therefore, the statement "True" is an accurate description of the role of sGC as an NO receptor that synthesizes cGMP.

Phosphodiesterase is responsible for breaking down cAMP. cAMP is a secondary messenger molecule that plays a crucial role in signal transduction within cells. It activates various cellular processes by binding to and activating protein kinases. However, cAMP needs to be regulated to prevent prolonged activation of these processes. Phosphodiesterase breaks down cAMP into AMP, terminating its signaling function. Adenylyl cyclase is responsible for synthesizing cAMP, Troponin is a protein involved in muscle contraction, and ATPase is an enzyme that hydrolyzes ATP.

c-Myc is a regulator gene that codes for a transcription factor. Transcription factors are proteins that bind to specific DNA sequences and regulate the expression of genes. c-Myc is a well-known transcription factor that plays a critical role in cell growth and proliferation. It is involved in various cellular processes, including cell cycle progression, apoptosis, and cellular transformation. Dysregulation of c-Myc can lead to the development of cancer. Therefore, c-Myc is a regulator gene that codes for a transcription factor.

The IP3/DAG pathway can be activated intracellularly via tyrosine kinase. Tyrosine kinases are enzymes that add a phosphate group to tyrosine residues in proteins. When activated, tyrosine kinases can phosphorylate and activate various downstream signaling molecules, including phospholipase C (PLC), which then cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 then binds to its receptor on the endoplasmic reticulum, leading to the release of calcium ions and activation of downstream signaling pathways. Therefore, tyrosine kinase activation can trigger the IP3/DAG pathway.

When ATP is converted to cAMP, it activates protein kinase A. This is because cAMP binds to the regulatory subunits of protein kinase A, causing the catalytic subunits to be released and become active. This activation of protein kinase A leads to phosphorylation of target proteins, which can result in various physiological effects. Additionally, stimulatory ligands bind to stimulatory receptors and activate adenylyl cyclase via Gs. Adenylyl cyclase then catalyzes the conversion of ATP to cAMP, further activating protein kinase A and leading to physiological effects.

The statement is false because IP3 and DAG pathway can be activated intracellularly via activation of phospholipase Cγ, not phospholipase Cβ.

The NO/cGMP signaling pathway is the most studied signaling pathway and occurs in many tissues including the cardiac and neural systems. Nitric oxide (NO) is a small molecule that acts as a signaling molecule in the body. It activates the enzyme guanylate cyclase, which then produces cyclic guanosine monophosphate (cGMP). cGMP acts as a second messenger and regulates various physiological processes such as smooth muscle relaxation, neurotransmission, and cardiac function. The NO/cGMP pathway has been extensively studied due to its involvement in numerous physiological and pathological processes, making it the most studied signaling pathway.