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AP Biology Chapter 11
Terms in this set (50)
What is a signal transduction pathway?
A signal transduction pathway is the series of steps by which a signal from outside the cell is converted (transduced) into a functional change within the cell.
How does yeast mating serve as an example of a signal transduction pathway?
Yeast cells use chemical signaling to identify cells of opposite mating type (a and α) and initiate the mating process.
Numerous cells can simultaneously receive and respond to molecules of growth factor
(consisting of compounds that stimulate nearby target cells to grow and divide) produced by a
single cell in their vicinity
An electrical signal along a nerve cell triggers the secretion of neurotransmitter molecules
carrying a chemical signal that diffuse across the synapse, triggering a response in a target cell
How does a hormone qualify as a long-distance signaling example?
In endocrine signaling (hormonal signaling in animals), hormone molecules are released by specialized cells, which travel to other parts of the body through the circulatory system to reach target cells that recognize and respond to the
hormones. Plant hormones (plant growth regulators) sometimes travel in vessels but more often reach their targets by moving through cells or by diffusing through the air as a gas.
What are the three stages of signal transduction pathway?
Reception, Transduction, Response
The target cell's detection of a signaling molecule coming from outside the cell, a chemical signal is
"detected" when the signaling molecule binds to a receptor protein located at the cell's surface or inside the cell.
The signal is converted to a form that can bring about a specific cellular response. The binding of the signaling molecule changes the receptor protein in some way, initiating the second stage.
Triggered by the transduced signal may be almost any imaginable cellular activity.
Explain the term ligand. (This term is not restricted to cell signaling. You will see it in other situations during the year.)
A ligand is a molecule that specifically binds to another molecule, often a larger one. Ligand binding generally causes the receptor protein to undergo a chance in shape.
The text will explain three major types of membrane receptors in Figure 11.7. This material is of fundamental importance, so we will work thorough the specific figures for each type of membrane receptor. The first example is a G protein-linked receptor. In the first figure, label the components and then describe the role of the three components.
Describe what happens in the second stage.
When the appropriate signaling molecule binds to the extracellular side of the receptor, the receptor is activated and changes shape. Its cytoplasmic side then binds an inactive G protein, causing a GTP to displace the GDP. This activates the G protein.
9. Describe what happens in the third stage. !
The activated G protein dissociates from the receptor, diffuses along the membrane, and then binds to an enzyme, altering the enzyme's shape and activity. Once activated, the enzyme can trigger the next step leading to a cellular response. Binding of signaling molecules is reversible.
10. Describe how the signal is halted. !
The G protein also functions as a GTPase enzyme: it hydrolyzes its bound GTP to GDP. Now inactive again, the G protein leaves the enzyme, which returns to its original state. The G protein is now available for reuse.
What activates a G protein?
The GTPase function of the G protein allows the pathway to shut down rapidly when the signaling molecule is no longer present.
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