Mastering Biology Chapter 11 Flashcards

Questions and Answers

Which of these is a receptor molecule?

Option 4

Option 3

Option 2 (correct)

Option 1

A signal transduction pathway is initiated when a _____ binds to a receptor.

signal molecule

Which of these is a signal molecule?

Option 1 (correct)

Option 3

Option 2

Option 4

A signal molecule is also known as a(n) ____.

ligand Signup and view all the answers

Which of these is the second of the three stages of cell signaling?

Transduction Signup and view all the answers

Complete the flowchart describing the interaction of cortisol with intracellular receptors.

<ol> <li>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.</li> </ol> Signup and view all the answers

What do G protein-coupled receptors do?

Interact directly with G proteins. Signup and view all the answers

What catalyzes the transfer of a phosphate group to the receptor in receptor tyrosine kinases?

Catalyzes the transfer of a phosphate group to the receptor. Signup and view all the answers

What binds the signaling molecules to both types of receptors?

Binding site for signaling molecule is located on the extracellular side of the cell. Signup and view all the answers

Binding of the signaling molecule allows ions to flow through a channel in the receptor.

False Signup and view all the answers

Which statements are true about the binding of histamine to the histamine H1 receptor?

Histamine binds extracellularly to the H1 receptor. When histamine binds, the receptor undergoes a conformation change and binds the inactive G protein. Once active, it binds to phospholipase C, activating it. Histamine is likely hydrophilic. Signup and view all the answers

Which of these acts as a second messenger?

Cyclic AMP Signup and view all the answers

Which of these is responsible for initiating a signal transduction pathway?

A Signup and view all the answers

What role does a transcription factor play in a signal transduction pathway?

By binding to DNA it triggers the transcription of a specific gene. Signup and view all the answers

Which of these is a membrane receptor?

G protein-coupled receptor Signup and view all the answers

Calcium ions that act as second messengers are stored in ____.

endoplasmic reticula Signup and view all the answers

___ catalyzes the production of _, which then opens an ion channel that releases ___ into the cell's cytoplasm.

Phospholipase C...IP3....Ca2+. Signup and view all the answers

A protein kinase activating many other protein kinases is an example of ____.

amplification Signup and view all the answers

What is apoptosis?

controlled cell suicide Signup and view all the answers

What hypothesis was being tested with the ΔFus3 strain?

Formin is required for the signal transduction pathway leading to shmoo formation. Signup and view all the answers

What hypothesis was being tested with the Δformin strain?

Formin is required for the signal transduction pathway leading to shmoo formation. Signup and view all the answers

What is the purpose of including wild-type yeast cells in the experiment?

To show normal shmoo formation under the experimental conditions. Signup and view all the answers

If the hypothesis that Fus3 kinase is required for the signal transduction pathway leading to shmoo formation is correct, what result should be observed in the ΔFus3 strain?

The ΔFus3 strain should not form shmoos, and the cells should not have a red zone in their walls. Signup and view all the answers

If the hypothesis that formin is required for the signal transduction pathway leading to shmoo formation is correct, what result should be observed in the Δformin strain?

The Δformin strain should not form shmoos, and the cells should not have a red zone in their walls. Signup and view all the answers

What would you predict would happen if the yeast had a mutation that prevented the G protein from binding GTP?

No shmoo would form in response to mating factor Signup and view all the answers

Match the following processes with their descriptions:

Reception = Signaling molecule binds to receptors Transduction = Signal is transmitted through a cascade Response = Cellular change occurs as a result of signaling Signup and view all the answers

Study Notes

Cell Signaling Overview

Receptor molecules, such as G protein-coupled receptors and receptor tyrosine kinases, initiate cell signaling pathways when a signal molecule (ligand) binds to them.
Signal transduction pathways consist of three main stages: reception, transduction, and response.

Key Components of Signal Transduction

Signal Molecules (Ligands): Chemicals that bind to receptors to initiate signaling, e.g., cortisol.
Transduction: The process where the signal is converted into a response, often involving secondary messengers like cyclic AMP and calcium ions.
Receptors:
- G protein-coupled receptors interact directly with G proteins.
- Receptor tyrosine kinases transfer phosphate groups upon activation.
- Binding sites for signaling molecules are located extracellularly.

Cortisol Mechanism

Cortisol passes through the plasma membrane, forms a complex with intracellular receptors, and acts as a transcription factor in the nucleus to regulate gene expression.

Histamine Signaling

Histamine activates the H1 receptor (a G protein-coupled receptor), leading to conformational changes and G protein activation.
Phospholipase C cleaves PIP2 to generate second messengers, DAG and IP3; IP3 triggers calcium ion release from the endoplasmic reticulum, increasing cytosolic calcium concentrations.

Apoptosis

Apoptosis is a controlled process of programmed cell death, crucial for maintaining cellular homeostasis.

Experimental Design in Yeast Studies

The ΔFus3 and Δformin yeast strains were tested to evaluate the role of Fus3 kinase and formin in the signal transduction pathway leading to shmoo formation.
Wild-type strains serve as controls to compare normal and mutant responses.
The outcome of forming shmoos in response to mating factors indicates successful signaling pathways.

Key Hypotheses and Predictions

If formin and Fus3 kinase are required for shmoo formation, mutations that prevent their function (ΔFus3 and Δformin strains) should result in the absence of shmoo formation.
Predictions support that lack of G protein binding to GTP results in no shmoo formation in yeast.

Why Different Responses Occur

Variability in response to histamine is attributed to:
- Different relay molecules present in cells.
- Specific enzymes activated by G proteins.
- Types of second messengers involved.
- Cell types where histamine receptors are located.

Shmoo Formation Mechanism

Shmoo projections emerge on the side of yeast cells that bound mating factors due to localized activation of formin by G protein-coupled receptor signaling, resulting in polarized growth responses.

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Test your knowledge of key concepts from Chapter 11 of Mastering Biology. This quiz covers important terms such as receptor molecules and signal transduction pathways, which are crucial for understanding cellular communication. Perfect for students looking to reinforce their learning in this subject area.