Marks Chapter 11 Cell Signaling By Chemical Messengers Quiz

Explanation
Hormones are the chemical messengers of the endocrine system. They are produced by various glands in the body and are released into the bloodstream, where they travel to target cells and organs to regulate various bodily functions and processes. Hormones play a crucial role in maintaining homeostasis, growth and development, metabolism, reproduction, and many other physiological processes. Therefore, the correct answer is hormones.

Explanation
Autocrine transmitters are signaling molecules that act on the same cell or nearby cells of the same type. This means that they are produced and released by a cell and then bind to receptors on the same cell or neighboring cells of the same type, resulting in a cellular response. This autocrine signaling allows cells to communicate with each other and regulate their own behavior. Therefore, the given answer "True" is correct.

Explanation
Paracrine receptors are the type of receptors that travel to nearby cells. These receptors are responsible for signaling between cells in close proximity to each other. Unlike endocrine receptors that release hormones into the bloodstream to act on distant cells, paracrine receptors release signaling molecules that act on neighboring cells. This allows for local communication and coordination between cells within a specific tissue or organ. Hypocrine and autocrine are not types of receptors, and endocrine receptors do not travel to nearby cells.

Explanation
Acetylcholine release is triggered by the influx of calcium ions (Ca^2+) into the cell. Calcium ions play a crucial role in the process of neurotransmitter release. When an action potential reaches the presynaptic terminal, voltage-gated calcium channels open, allowing calcium ions to enter the cell. This influx of calcium triggers the fusion of synaptic vesicles containing acetylcholine with the presynaptic membrane, leading to the release of acetylcholine into the synaptic cleft. Therefore, calcium ions are necessary for the release of acetylcholine, making Ca^2+ the correct answer.

Explanation
Nicotinic acetylcholine receptors are ion channels that are found in the cell membranes of neurons and other cells. These receptors have a complex structure consisting of multiple subunits. Each subunit contains several membrane-spanning helical regions, which are responsible for forming the ion channel pore. The question asks for the total number of membrane-spanning helical regions in the receptor. The correct answer is 20, indicating that each subunit of the receptor has five membrane-spanning helical regions.

Explanation
When acetylcholine binds to a nicotinic acetylcholine receptor, the channel allows Na+ ions to diffuse into the cell and K+ ions to diffuse out. This is because the nicotinic acetylcholine receptor is a ligand-gated ion channel that is permeable to both Na+ and K+ ions. The binding of acetylcholine causes a conformational change in the receptor, leading to the opening of the channel and the movement of ions across the cell membrane.

Explanation
Endocrine hormones are chemical messengers secreted by endocrine glands into the bloodstream to target distant organs. However, some endocrine hormones can also act locally on nearby cells, either in a paracrine or autocrine manner. Paracrine actions occur when the hormone acts on neighboring cells, while autocrine actions occur when the hormone acts on the same cells that produced it. Therefore, it is true that many endocrine hormones exhibit paracrine or autocrine actions in addition to their endocrine effects.

Explanation
Thyroid hormones, such as thyroxine (T4) and triiodothyronine (T3), are derived from the amino acid tyrosine. Tyrosine is converted into a molecule called thyroglobulin, which is then further modified to produce thyroid hormones. These hormones play a crucial role in regulating metabolism, growth, and development in the body. Therefore, tyrosine is the correct amino acid from which thyroid hormones are derived.

Explanation
Some hormones can also function as neurotransmitters. Neurotransmitters are chemicals that transmit signals between nerve cells in the brain and other parts of the body. Hormones, on the other hand, are chemical messengers that are released into the bloodstream and travel to target cells or organs to regulate various bodily functions. However, some hormones, such as adrenaline and dopamine, can also act as neurotransmitters in the brain, transmitting signals between neurons. Therefore, it is true that some hormones can also function as neurotransmitters.

Explanation
Epinephrine is classified as a catecholamine. Catecholamines are a class of neurotransmitters and hormones that are derived from the amino acid tyrosine. Epinephrine, also known as adrenaline, is produced by the adrenal glands and acts as a hormone and neurotransmitter in the body. It plays a key role in the body's response to stress, increasing heart rate, blood pressure, and glucose levels, and preparing the body for "fight or flight" response. Catecholamines are not polypeptide hormones, thyroid hormones, or steroid hormones.

Explanation
Eicosanoids are a group of signaling molecules that play important roles in inflammation and other physiological processes. They are derived from arachidonic acid, which is a polyunsaturated fatty acid found in cell membranes. When cells are stimulated, arachidonic acid is released and converted into various eicosanoids, such as prostaglandins, leukotrienes, and thromboxanes. These eicosanoids then act as local hormones, regulating inflammation, blood clotting, and other responses. Glutamic acid, tyrosine, and glutamate are not involved in the synthesis of eicosanoids.

Explanation
Messengers that use intracellular receptors must be hydrophobic because these receptors are located inside the cell, which is primarily composed of hydrophobic lipid bilayers. Hydrophobic messengers can easily pass through the cell membrane and bind to their specific intracellular receptors, initiating signal transduction pathways and cellular responses. Hydrophilic molecules, on the other hand, cannot easily cross the cell membrane and therefore cannot interact with intracellular receptors. Small hydrophobic molecules are more likely to diffuse through the membrane than larger macromolecules, making them suitable messengers for intracellular signaling.

Explanation
The statement is false because the steroid hormone/thyroid hormone superfamily of receptors does not primarily reside in the cytoplasm. These receptors are primarily located in the nucleus of cells, where they bind to specific DNA sequences and regulate gene expression. While some of these receptors may also be found in the cytoplasm, their primary localization is in the nucleus.

Explanation
The correct answer is MAPKKK. MAPKKK stands for Mitogen-Activated Protein Kinase Kinase Kinase, which is a type of protein involved in the activation of the MAP kinase signaling pathway. The Raf protein is a well-known example of a MAPKKK, and it plays a crucial role in transmitting signals from cell surface receptors to the nucleus, ultimately leading to various cellular responses such as cell growth and differentiation.

Explanation
A G-protein receptor is a heptahelical receptor. This type of receptor has seven transmembrane domains, which allows it to interact with G-proteins and initiate intracellular signaling pathways. G-protein receptors are involved in a wide range of physiological processes and are found in various tissues and cell types throughout the body. They play a crucial role in mediating the effects of hormones, neurotransmitters, and other signaling molecules.

Explanation
The correct answer is Tyrosine Kinase receptor. The insulin receptor is a type of receptor that belongs to the tyrosine kinase family. Tyrosine kinase receptors are characterized by their ability to phosphorylate tyrosine residues in target proteins, leading to the activation of various signaling pathways. In the case of the insulin receptor, binding of insulin to the receptor leads to autophosphorylation of tyrosine residues in the receptor itself, initiating a cascade of events that regulate glucose uptake and metabolism in cells.

Explanation
Insulin does not cause the insulin receptor to dimerize. In fact, insulin binds to the alpha subunits of the insulin receptor, causing a conformational change that allows the beta subunits to phosphorylate each other. This phosphorylation event is what leads to the activation of downstream signaling pathways. Dimerization of the insulin receptor occurs through the binding of insulin, but it is not caused by insulin itself. Therefore, the statement is false.