Questions and Answers
What is a signal transduction pathway?
Process by which a signal on a cell's surface is converted to a specific cellular response in a series of steps.
How does yeast mating serve as an example of a signal transduction pathway?
Alpha yeast sends alpha signals that A yeast receives. A yeast sends A signals that only alpha can receive. The respective signals are then transduced and a response is carried out (mating).
What is paracrine signaling?
Secreting cells send regulators to target cells and to all cells in the vicinity. Examples are animal cells and growth hormones.
What is synaptic signaling?
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How does a hormone qualify as a long-distance signaling example?
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What is reception in cell signaling?
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What is transduction in cell signaling?
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What is a response in cell signaling?
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What is a ligand?
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What activates a G protein?
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Why is the fact that a G protein is also a GTPase enzyme important?
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What does a kinase enzyme do?
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How does tyrosine kinase function in the membrane receptor?
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What is a key difference between receptor kinases and G protein-coupled receptors?
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Each activated protein in tyrosine kinase triggers a signal ______ pathway leading to a ______ response.
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In what body system are ligand-gated ion channels and voltage-gated ion channels of particular importance?
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Intracellular receptors are found in the ______ or ______ of the cell, where they bond to chemical messengers that are _____ or very small, like nitric acid.
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What are transcription factors?
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What are two benefits of multistep pathways?
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What is the role of protein kinase?
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What is the role of protein phosphatases?
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What is the difference between a first messenger and a second messenger?
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What is the role of cAMP?
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Explain the mechanism of disease in cholera.
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List three pathways often induced by calcium ions.
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What happens to the cytoplasmic concentration of calcium when it is used as a second messenger?
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When cell signaling causes a response in the nucleus, what normally happens?
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When cell signaling causes a response in the cytoplasm, what normally happens?
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How do scaffolding proteins enhance a cellular response?
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What specifically happens to a cell during the process of apoptosis?
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Give one example of a signal for apoptosis coming from outside the cell, and two from inside the cell.
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Study Notes
Signal Transduction Pathways
- Signal transduction pathways convert external signals into specific cellular responses through a series of steps.
- Yeast mating exemplifies this by using alpha and A signals, leading to mating responses upon transduction.
Types of Signaling
- Paracrine signaling: Local regulators secreted by cells affect nearby target cells; common in growth factor signaling in animals.
- Synaptic signaling: Electrical signals trigger the release of neurotransmitters to specifically affect target cells, ensuring precise communication.
Hormone Signaling
- Hormones serve as long-distance signals that circulate throughout the body via the bloodstream, reaching various target cells.
Basic Concepts of Cell Signaling
- Reception: Involves detecting signaling molecules by target cells.
- Transduction: Converts signals into forms that elicit specific cellular responses.
- Response: The final outcome from the transduced signal, resulting in specific cellular activities.
Molecular Components
- Ligands: Molecules that specifically bind to larger molecules (receptors).
- G proteins: Activated by signaling proteins, they undergo shape changes and bind to enzymes to propagate signals.
- GTPase activity: A G protein’s ability to hydrolyze GTP to GDP halts signal transmission.
Enzymatic Roles
- Kinase enzymes: Catalyze phosphorylation, transferring phosphate groups to proteins, thereby altering their function.
- Tyrosine kinase: Activates various signal transduction pathways by modifying receptor configuration.
- Protein phosphatases: Remove phosphate groups from proteins, reversing the effects of kinases.
Signaling Pathways Comparison
- Receptor kinases can activate multiple signal transduction pathways, unlike G protein-coupled receptors which typically activate a single pathway.
Cellular Mechanisms
- Ligand-gated and voltage-gated ion channels play critical roles in the nervous system.
- Intracellular receptors, found in the cytoplasm or nucleus, bind hydrophobic chemical messengers like nitric oxide.
Transcription Factors and Cellular Regulation
- Transcription factors are protein complexes that regulate gene expression by controlling mRNA transcription in response to signals.
Advantages of Multistep Pathways
- Multistep pathways amplify signals and provide enhanced regulation of cellular responses.
Secondary Messengers
- cAMP: A secondary messenger that activates protein kinase A, promoting cellular responses.
- Calcium ions: Serve as crucial secondary messengers, their concentrations increase to facilitate various signaling pathways.
Cellular Responses to Signaling
- In the nucleus, signaling typically results in the activation of transcription factors affecting gene expression.
- In the cytoplasm, signaling leads to the regulation of protein activity.
Scaffolding Proteins
- Scaffolding proteins improve the speed and accuracy of cellular responses by localizing signaling molecules and enhancing interactions.
Apoptosis Process
- Apoptosis features DNA fragmentation, cell shrinkage, membrane lobing, vesicle formation, and subsequent digestion by scavenger cells.
Apoptosis Signals
- External signals: Death signaling molecules interact with Ced-9 to trigger apoptosis.
- Internal signals: Include mitochondrial leakage and stress from misfolded proteins in the endoplasmic reticulum.
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Description
Explore key concepts of 'Cell Communication' in AP Biology with these flashcards. Understand the processes involved in signal transduction pathways and their examples, such as yeast mating. Perfect for reinforcing your knowledge before exams.