A signal transduction pathway is initiated when a _____ binds to a receptor.
answer
Signal Molecule
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Which of these is a signal molecule?
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A
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A signal molecule is also known as a(n) _____.
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ligand
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Which of these is the second of the three stages of cell signaling?
answer
Transduction
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Cortisol is a steroid hormone that can pass through the plasma membrane. Complete the flowchart describing the interaction of cortisol with intracellular receptors.
answer
1) cortisol passes through the plasma membrane into the cytoplasm
2) cortisol-receptor complex forms in the cytoplasm
3) cortisol-receptor complex enters the nucleus where it binds to genes
4) cortisol-receptor complex acts as a transcription factor
5) the transcribed mRNA is translated into a specific protein
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G protein-coupled receptors
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interact directly with G proteins
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Receptor tyrosine kinases
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-catalyzes the transfer of a phosphate group to the receptor
-binding of the signaling molecules forms a dimer
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Both types of receptors
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-binding site for signaling molecule is located on the extracellular side of the cell
-receptor is located in the plasma membrane
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Neither receptor
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binding of the signaling molecule allows ions to flow through a channel in the receptor
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Which statements are true about the binding of histamine to the histamine H1 receptor?
answer
-Histamine binds extracellularly to the H1 receptor.
-When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein.
-Once the G protein is active, it binds to the enzyme phospholipase C, activating it.
-Histamine is likely hydrophilic.
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Which of these acts as a second messenger?
answer
d
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Which of these is responsible for initiating a signal transduction pathway?
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A
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What role does a transcription factor play in a signal transduction pathway?
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By binding to DNA it triggers the transcription of a specific gene.
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Which of these is a membrane receptor?
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B
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A signal transduction pathway is initiated when a _____ binds to a receptor.
answer
signal molecule
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Which of these acts as a second messenger?
answer
cyclic AMP
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Calcium ions that act as second messengers are stored in _____.
answer
endoplasmic reticula
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_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm.
answer
Phospholipase C ... IP3 .... Ca2+
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A protein kinase activating many other protein kinases is an example of _____.
-adenylyl cyclase, cAMP, IP3, phosphorylation cascade, second messenger, Ca2+
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Response
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protein synthesis
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Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine.
Show the process of histamine signal transduction from the H1 receptor.
answer
1. Enzyme cleaves PIP2, forming DAG and IP3.
2. IP3 binds to a ligand-gated ion channel in the ER membrane.
3. Calcium ions flow through the ligand-gated ion channel.
4. Calcium ion concentration increases in the cytosol.
5. Calcium ions activate a protein, leading to a cellular response.
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Which of the following could account for the different cellular responses to histamine? Select all that apply.
answer
- the types of relay molecules within the cell
- the enzyme that is activated by the G protein associated with the receptor
- the type of second messengers involved in the signal transduction pathway
- the cell type in which the histamine receptor is located
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What is apoptosis?
answer
controlled cell suicide
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What hypothesis was being tested with the ΔFus3 strain?
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Formin is required for the signal transduction pathway leading to shmoo formation.
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What hypothesis was being tested with the Δformin strain?
answer
Formin is required for the signal transduction pathway leading to shmoo formation.
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In addition to testing shmoo formation in the two mutant strains of yeast, the scientists also tested shmoo formation in wild-type yeast.
What is the purpose of including wild-type yeast cells in the experiment?
answer
to show normal shmoo formation under the experimental conditions
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When designing an experiment, scientists make predictions about what results will occur if their hypothesis is correct.
One of their hypotheses was that Fus3 kinase is required for the signal transduction pathway leading to shmoo formation. If this hypothesis is correct, what result should be observed in the ΔFus3 strain?
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The ΔFus3 strain should not form shmoos, and the cells should not have a red zone in their walls.
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One of their hypotheses was that formin is required for the signal transduction pathway leading to shmoo formation. If this hypothesis is correct, what result should be observed in the Δformin strain?
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The Δformin strain should not form shmoos, and the cells should not have a red zone in their walls.
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The micrographs shown below were taken of wild-type, ΔFus3, and Δformin cells after they were stained green, exposed to mating factor, and then stained red.
For each micrograph, drag the labels to answer the questions. Labels may be used once, more than once, or not at all.
answer
Wild Type: Red Green - Asym - Y - Y - Y
ΔFus3: Yellow - Sym - N - Y - Y
Δformin: Yellow - Sym - N - Y - Y
question
Fus3 kinase and formin proteins are generally distributed evenly throughout a yeast cell. Based on the model in the diagram, why does the shmoo projection emerge on the same side of the cell that bound the mating factor?
answer
The only formin molecules that get phosphorylated and thus activated are those near the G protein-coupled receptor that binds mating factor.
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What do you predict would happen if the yeast had a mutation that prevented the G protein from binding GTP?
answer
No shmoo would form in response to mating factor.
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