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Identify and describe the three stages of the signal transduction pathway.

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Identify and describe the three stages of the signal transduction pathway.

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There are three stages in a signal transduction pathway: reception, transduction, and response. Reception occurs when the target cell detects a signaling molecule and a signal molecule binds to a receptor protein in the cell or on the surface of the cell. Next, transduction occurs when the signal travels across the transduction pathway. Transduction converts the signal to a form that allows for the cell to respond to it. Transduction can occur in a single step, but sometimes more changes are required as the signal travels; molecules that are along this path are called relay molecules. Lastly, response occurs when the transduced signal triggers a specific response from the cell.

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Differentiate between the types of local and long distance signaling

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Differentiate between the types of local and long distance signaling

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Cells can communicate through types of local signaling, such as: paracrine signaling, synaptic signaling, or direct contact. In paracrine signaling, a single cell produces growth factors and sends them to cells in the direct vicinity; the cells simultaneously receive and respond to the signal. In synaptic signaling, a nerve cell produces a neurotransmitter that is diffused to a single nearby cell. In direct contact, signaling chemicals in the cytosol of cell are passed freely between them, or substances on the cells’ surfaces may be used in direct contact.

Cells can also communicate over long distances with hormone signaling; this occurs when endocrine cells release hormones into the cardiovascular system of animals; however,  in plant cells, hormones can travel through vessels, directly from cell to cell, or diffuse into the air. Local and long distance cell communication methods all allow cells to communicate and regulate growth, however, each method differs from the others in the process.

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Explain why a specific signal can elicit a different response or no response at all from different cell types.

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Explain why a specific signal can elicit a different response or no response at all from different cell types.

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A specific signal can elicit a certain response depending on the type of cell since signal molecules bind to specific receptors in cells. The way a cell responds to the signal is also specific to the type of cell. Cellular responses to signals are determined by the different proteins in cells. The different types of signal proteins, relay proteins, and response proteins determine the specific cellular response of a cell.

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A ligand is any molecule that bonds specifically to a receptor site of another molecule.

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Which receptor mechanism is especially good for triggering several pathways at once?  How can this mechanism do this?

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Which receptor mechanism is especially good for triggering several pathways at once?  How can this mechanism do this?

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Tyrosine-kinase receptors are good for triggering several pathways at once since they can activate multiple transduction pathways and cellular responses. This kind of receptor has two membrane receptors and two intracellular tails that each have multiple tryosine amino acids. When both receptors are activated by a signal molecule, each tyrosine amino acid on the tails is phosphorylated and is capable of activating a different signal-transduction pathway.

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Transduction is the conversion of one form of energy to another. In a signal transduction pathway, the signal molecule is transduced to cause the cell to respond in a specific way to the signal. An example is how our brains process environmental stimuli and energy to create what we know as senses like sight, sound, smell, feel, and taste.

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A phosphorylation cascade is a chain reaction that results in the phosphorylation of thousands of proteins. It is caused when one enzyme phosphorylates another enzyme, then that enzyme phosphorylates another enzyme, and then that sequence continues, like a chain reaction. The end result is thousands of phosphorylated enzymes that all resulted from the first phosphorylation of an enzyme.

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Research type II diabetes and explain the disorder in terms of signal transduction pathways.

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Research type II diabetes and explain the disorder in terms of signal transduction pathways.

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Type II diabetes is caused by what is known as insulin resistance. When the body breaks down food, glucose is released into the bloodstream. In response to the elevated level of glucose in the blood, the pancreas released a hormone called insulin. Insulin travels through the bloodstream to fat cells; insulin binds to the extracellular part of insulin receptors located on fat cells. Normally, insulin binds to the insulin receptor, which sends a signal to the intracellular part of the receptor, which then activates and activates proteins in the fat cell. Certain processes, most relating to energy storage, are regulated by the phosphorylation of activated proteins in the fat cell. These different pathways cause the cell to respond by taking in glucose from the bloodstream, which returns blood glucose levels to normal. In type II diabetes, insulin is able to bind to the extracellular part of an insulin receptor on a fat cell, but no signal is transduced in the cell; this causes there to be no cellular response, meaning that no glucose is taken in by the fat cell. As a result of high levels of glucose being left in the bloodstream, damage can occur to many organs. In brief, type II diabetes is caused by a signal that is unable to be transduced by a receptor, and in turn, no cellular response is triggered.

Sources: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3617287/
https://www.wehi.edu.au/wehi-tv/insulin-receptor-and-type-2-diabetes

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All images are figures from Campbell Biology 9th Edition, Chapter 11.