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Questions and Answers
What is the primary function of cyclic guanosine monophosphate (cGMP) as a second messenger?
What is the primary function of cyclic guanosine monophosphate (cGMP) as a second messenger?
Which of the following is NOT an example of a second messenger?
Which of the following is NOT an example of a second messenger?
Which gas is considered a second messenger that can signal to neighboring cells?
Which gas is considered a second messenger that can signal to neighboring cells?
Which of the following ions can act as a second messenger within cellular compartments?
Which of the following ions can act as a second messenger within cellular compartments?
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What structural component is featured in the cyclic structures of cyclic monophosphates such as cAMP and cGMP?
What structural component is featured in the cyclic structures of cyclic monophosphates such as cAMP and cGMP?
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What best defines cell signal transduction?
What best defines cell signal transduction?
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Which of the following is a type of intercellular signaling?
Which of the following is a type of intercellular signaling?
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What role do ligands play in cell signaling?
What role do ligands play in cell signaling?
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Which of the following statements about receptors is true?
Which of the following statements about receptors is true?
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Which of the following is NOT a step in the process of intercellular signaling?
Which of the following is NOT a step in the process of intercellular signaling?
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What distinguishes intracellular signaling from intercellular signaling?
What distinguishes intracellular signaling from intercellular signaling?
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Which molecule is an example of a second messenger in cell signaling?
Which molecule is an example of a second messenger in cell signaling?
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What is the primary function of carrier proteins in cell signaling?
What is the primary function of carrier proteins in cell signaling?
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What is the primary role of specific receptors in signal reception?
What is the primary role of specific receptors in signal reception?
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Which of the following accurately describes transduction in signal transduction pathways?
Which of the following accurately describes transduction in signal transduction pathways?
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How does the endocrine signaling differ from paracrine signaling?
How does the endocrine signaling differ from paracrine signaling?
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Which type of cellular signaling involves the quickest responses?
Which type of cellular signaling involves the quickest responses?
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What initiates the intracellular signaling pathways after signal reception?
What initiates the intracellular signaling pathways after signal reception?
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What is NOT a characteristic of endocrine signaling?
What is NOT a characteristic of endocrine signaling?
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What type of signaling connects cells directly, allowing for immediate response?
What type of signaling connects cells directly, allowing for immediate response?
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What is the function of protein kinases in signal transduction?
What is the function of protein kinases in signal transduction?
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What is the primary function of autocrine signaling?
What is the primary function of autocrine signaling?
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Which type of signal can pass through gap junctions during direct signaling?
Which type of signal can pass through gap junctions during direct signaling?
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What is the role of internal receptors in cellular signaling?
What is the role of internal receptors in cellular signaling?
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Which process involves the addition of a phosphate group to a protein, potentially altering its function?
Which process involves the addition of a phosphate group to a protein, potentially altering its function?
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What characterizes enzyme-linked receptors in cell signaling?
What characterizes enzyme-linked receptors in cell signaling?
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What mechanism do G-protein-linked receptors use to propagate cellular signals?
What mechanism do G-protein-linked receptors use to propagate cellular signals?
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Which of the following is NOT a type of cell-surface receptor?
Which of the following is NOT a type of cell-surface receptor?
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What is the main role of second messengers in intracellular signaling?
What is the main role of second messengers in intracellular signaling?
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Study Notes
Cell Signal Transduction
- The process of how a cell responds to external chemical signals.
- Crucial for communication between cells and regulating various biological processes.
Cell Signalling Types
- Intercellular signalling: Communication between cells
- Intracellular signalling: Signalling chains within the cell, responding to extracellular and intracellular stimuli
Intercellular Signalling in Eukaryotes
- Coordinates vital functions, ensuring maintenance and function of specialized tissues and organs.
- Functions include cell growth, division, motility, and morphology.
Signalling Receptors
- Protein molecules that bind to ligands, initiating a cellular response.
- Ligands are molecules that attach to specific receptors on a cell to trigger a biological response.
- Ligands act as "keys" that bind to "locks" (receptors) on the cell.
- A specific ligand will have a specific receptor.
- Receptors are essential for cell communication and response.
Steps of Intercellular Signalling
- Formation: An external trigger causes the production/release of signaling molecules (e.g., hormones) from specialized cells.
- Signal Transport: The signal travels to the target cell, often via circulation or diffusion, sometimes with carrier proteins.
- Signal Reception: The target cell receives the signal through specific receptors, initiating intracellular signaling pathways.
- Signal Processing: The signal is converted into a biochemical response within the target cell, leading to specific cellular actions.
Stages of Cellular Signal Transduction
- Reception: Cells detect chemical signals through receptors.
- Transduction: The signal is converted into an internal response. Ligand binds to the receptor, changing the receptor's shape and activating the cell. Signal pathways often involve relay molecules that further amplify the signal.
- Response: The cell performs a specific action in response to the signal. Actions could include changes in gene expression, enzyme activity, or cell metabolism. Examples include protein kinases adding phosphate groups to proteins, or cell division, muscle contraction, or apoptosis.
Forms of Chemical Cell Signalling
- Paracrine: Signals act locally between nearby cells. Signals move by diffusion through the extracellular matrix. Elicit quick, short-lasting responses.
- Endocrine: Signals originate from distant endocrine cells. Located in endocrine glands like the thyroid, hypothalamus, and pituitary. Produce slower, longer-lasting effects. Hormones are released by glands into the bloodstream, where they travel long distances to target cells in different parts of the body.
- Autocrine: Signals produced and responded to by the same cell or similar cells. Signaling cell releases a signal that binds to its own receptors. Ensures proper tissue formation and function during early development.
- Direct signalling across gap junctions: Direct communication between neighboring cells through water-filled channels. Gap junctions in animals, plasmodesmata in plants. Small molecules like calcium ions (Ca2+) can pass through; larger molecules cannot.
Types of Receptors
- Internal Receptors: Found in the cytoplasm or nucleus. Respond to hydrophobic ligands that cross the plasma membrane. Regulate gene expression by binding to DNA after a ligand-induced conformational change.
- Cell-Surface Receptors: Transmembrane receptors. Bind external ligands without the ligands entering the cell. Specific to cell types and convert extracellular signals into intracellular actions.
Types of Cell-Surface Receptors
- Ion Channel-Linked Receptors: Open a channel through the membrane when a ligand binds, allowing specific ions to pass through and alter the cell's activity. Example: acetylcholine (nicotine receptor).
- G-Protein-Linked Receptors: Activate G-proteins upon ligand binding, which then interact with other membrane proteins to propagate the signal. G-proteins switch between active and inactive states to regulate cellular responses. Example: Dopamine.
- Enzyme-Linked Receptors: Have an intracellular domain that acts as an enzyme or associates with an enzyme. Ligand binding activates the enzyme, triggering a cascade of cellular events. Example: insulin receptor.
Examples of Common Events in Intracellular Signalling
- Phosphorylation: Adding a phosphate group to a protein by an enzyme called kinase, which can activate or deactivate the protein.
- Second Messengers: Intracellular, diffusible small molecules and ions that are quickly synthesized or released in response to signals from receptors, altering the activity of target signalling proteins.
Second Messengers (Examples)
- Cyclic nucleotides: Cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP)
- Lipid messengers: Originate within cell membranes, including inositol trisphosphate (IP3).
- Gases: Can signal throughout the cell and even to neighboring cells. Includes NO, CO, hydrogen sulphide (H2S).
- Ions: Signal within and between cellular compartments, including calcium (Ca2+), Na+, and K+.
cGMP (Cyclic Guanosine Monophosphate)
- Structure: Nucleotide with a sugar, guanine base, and a single phosphate group in a cyclic bond.
- Function: Second messenger in processes like smooth muscle contraction, phototransduction in the eye, and blood vessel dilation.
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Description
Explore the intricate process of cell signal transduction and the different types of cell signalling. Learn how cells communicate with each other through intercellular and intracellular signalling, along with the importance of receptors and ligands. Discover how these processes regulate critical biological functions in eukaryotic organisms.
