Cell Signaling Mechanisms

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Questions and Answers

Which type of receptors are most commonly found in the plasma membrane?

Intracellular receptors

Transcription factor receptors

Ion channel receptors

G protein-coupled receptors (GPCRs) (correct)

Phosphorylation is a process that relays a signal in a cell by removing a phosphate group.

False

What role do second messengers play in cell signaling?

They help relay the message of the signal and amplify the signal response.

Ligands that can bind to intracellular receptors typically include ______ molecules.

hydrophobic Signup and view all the answers

Match the following types of signal pathways with their descriptions:

Phosphorylation = Adds a phosphate group to relay signals Dephosphorylation = Removes a phosphate group to shut off signals Signal transduction pathway = Sequence of changes in molecules leading to a response cAMP = Common second messenger in signaling pathways Signup and view all the answers

What occurs when a ligand binds to a G protein coupled receptor (GPCR)?

GDP is converted to GTP Signup and view all the answers

Mutations in receptor proteins will not affect signal transduction pathways.

False Signup and view all the answers

What is the primary role of ligand gated ion channels?

To allow specific ion diffusion in response to ligand binding Signup and view all the answers

When a ligand binds to a receptor on a GPCR, the receptor undergoes a ________ change.

conformational Signup and view all the answers

Match the following components of signal transduction with their functions:

GPCR = Binds to G protein Ligand = Opens or closes ion channels G protein = Activates enzymes Enzyme = Amplifies cell response Signup and view all the answers

What type of junctions allows for the passage of substances between animal cells?

Gap junctions Signup and view all the answers

Paracrine signaling sends signals to distant cells.

False Signup and view all the answers

What is the primary function of plasmodesmata in plant cells?

To allow materials and signaling substances to pass freely between adjacent cells. Signup and view all the answers

In synaptic signaling, neurotransmitters diffuse across the ________ between a nerve cell and a target cell.

synaptic cleft Signup and view all the answers

Match the following types of signaling with their descriptions:

Paracrine signaling = Local regulators released to adjacent cells Synaptic signaling = Neurotransmitters released across a synaptic cleft Endocrine signaling = Hormones released into the bloodstream Direct contact = Signaling substances passed through cell junctions Signup and view all the answers

How do hormones reach their target cells in animals?

Via the circulatory system Signup and view all the answers

Small, nonpolar molecules easily pass through cell junctions in direct contact.

True Signup and view all the answers

What occurs during the reception step of cell signaling?

The detection and receiving of a ligand by a receptor in the target cell. Signup and view all the answers

Study Notes

Direct Contact Signaling

Cells communicate through cell junctions
Cytoplasm passes freely between cells in animals (gap junctions) and plants (plasmodesmata)
Small, nonpolar molecules pass easily through the cytoplasm
Gap junctions and plasmodesmata allow materials and signaling substances to pass between adjacent cells.

Local Regulators

Secreting cells release chemical messages (ligands) that travel short distances
Chemical messages cause a response in a target cell
Paracrine signaling: Secretory cells release local regulators (growth factors, hormones) via exocytosis to adjacent cells.
Synaptic signaling: Occurs in animal nervous systems; neurons release neurotransmitters that diffuse across the synaptic cleft (space between nerve and target cell) to nerves or muscles.
Local signaling is shorter distance than long distance signaling
Local signaling targets nearby cells, compared to longer distance signaling

Long Distance Signaling

Hormones are used for long-distance signaling
Plants use vascular tissue or the air to carry hormones to target tissues
Animals use endocrine signaling: specialized cells release hormones into the circulatory system to reach target cells.

Cell Signaling Steps

1. Reception

Ligand (chemical message) binds to receptor in target cell
This often triggers a conformational change (shape change) in the receptor protein
Receptors can be in the plasma membrane (e.g., most common) or intracellular (e.g., inside the cytoplasm)

2. Transduction

Conversion of extracellular signal to intracellular signal
This often involves a series of changes (signal transduction pathway) that often involves phosphorylation and dephosphorylation to regulate proteins.
Enzymes such as protein kinases add phosphate groups to proteins; protein phosphatases remove them
Second messengers (small, non-protein molecules) help relay message
Second messengers like cAMP increase signal amplification

3. Response

Final molecule in the signal transduction pathway alters cell processes
This can change membrane permeability, initiate enzyme activity, or alter gene expression
Ligand binding to receptor initiates a series of events that leads to a cellular response

GPCRs (G Protein-Coupled Receptors)

Largest category of cell surface receptors in animals
Important in animal sensory systems
Ligand binding to the GPCR activates GTP, in turn activating an enzyme or ion channel

Ion Channels

Important for nervous system function
Receptor acts as a gate for ions
Specific ion movement leads to cellular response when ligand binds.

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Description

Explore the fascinating world of cell communication through various signaling mechanisms. This quiz covers direct contact signaling, local regulators, and long-distance signaling methods. Test your knowledge on how cells interact and respond to their environment!