24 Questions
What is the primary function of endocrine ligands?
Targeting a distant cell through the bloodstream
What is the role of relay molecules in a signal transduction pathway?
They participate in the transduction of the signal
What is the initial transduction of the signal often triggered by?
A conformational change in the receptor
What is a characteristic of the binding between a signal molecule and a receptor?
It is highly specific
Where are most signal receptors located?
On the plasma membrane
What is the final stage of cell signaling?
Response
Which type of ligand targets cells near the original cell?
Paracrine ligand
What type of signaling requires cells to be in direct membrane-membrane contact?
Contact-dependent signaling
What is the primary function of second messengers in signal transduction?
To carry out various cellular functions such as sight, inflammation, and growth
What type of ligands can diffuse across the plasma membrane of target cells?
Hydrophobic ligands
What is the result of a ligand binding to a tyrosine kinase receptor?
Dimerization of the kinase domains
What is the function of G-protein coupled receptors (GPCRs)?
To activate an entire cascade of proteins (enzymes)
What is the role of ion channels in signal transduction?
To allow hydrophilic ions to pass through the plasma membrane
What is the result of a ligand binding to a G-protein coupled receptor?
Activation of an entire cascade of proteins (enzymes)
What type of receptors are involved in the binding of hydrophilic ligands?
Cell-surface receptors
What is the final outcome of signal transduction pathways?
A change in cellular behavior or response
What is the primary function of phosphatase enzymes in signal transduction pathways?
To remove phosphates from proteins
What is the role of adenylyl cyclase in signal transduction?
To convert ATP to cAMP
What is the function of G-proteins in signal transduction pathways?
To activate adenylyl cyclase
What is the primary function of kinases in signal transduction pathways?
To add phosphates to proteins
What is the term for the extracellular signal molecule that binds to the receptor in a signal transduction pathway?
First messenger
What is the primary function of second messengers in signal transduction pathways?
To participate in pathways initiated by G-protein-linked receptors and receptor tyrosine kinases
What is the term for the process by which a signal is transmitted through a series of protein activations?
Cascade of protein activations
What is the primary function of receptors in signal transduction pathways?
To bind to extracellular signal molecules
Study Notes
Types of Cell Signaling Molecules
- Endocrine ligands target distant cells through the bloodstream, e.g., hormones
- Paracrine ligands target cells near the original cell, e.g., neurotransmitters
- Autocrine ligands target themselves
- Contact-dependent ligands require direct membrane-to-membrane contact
Stages of Cell Signaling
- Reception: binding of signal molecule (ligand) to a receptor
- Transduction: conversion of the signal into a form that can bring about a response
- Response: change in behavior that occurs in the cell as a result of the signal
Reception
- Binding of a signal molecule (ligand) to a receptor is highly specific
- Conformational change in the receptor often initiates signal transduction
- Most signal receptors are plasma membrane proteins
Transduction
- Signal initiated by conformational change of receptors
- Process of activating a series of proteins inside the cell from the cell membrane, e.g., relay proteins and/or second messengers
Response
- Change in behavior that occurs in the cell as a result of the signal
Receptors
- Classified according to the type of ligands they bind
- Hydrophobic ligands (e.g., steroids, vitamin D3) bind to intracellular receptors
- Hydrophilic ligands bind to cell-surface receptors
Types of Cell-Surface Receptors
G-Protein Coupled Receptors (GPCRs)
- Receive a large number of signals from diverse groups
- Mechanism of action: ligand binds to receptor, activating G-protein, which activates enzymes and second messengers that carry out various functions
Tyrosine Kinase
- Ligand binds to the receptor, leading to dimerization of the kinase domains
- Phosphorylation of intracellular proteins allows them to bind and activate
Ion Channel
- Allow hydrophilic ions to pass through the plasma membrane
- Ligand binding opens the channel, e.g., neurotransmitters acting as ligands for Na+ ions
Signal Transduction Pathways
- Molecules relay a signal from receptor to response, usually proteins
- Signal transduction cascade: each protein activates the next, until the response is activated
- Protein Phosphorylation and Dephosphorylation: a cascade of protein phosphorylations (kinases) and dephosphorylations (phosphatases) acts as a molecular switch
Second Messengers
- Small, nonprotein, water-soluble molecules or ions
- Participate in pathways initiated by G-protein-linked receptors and receptor tyrosine kinases
- Examples: cyclic AMP (cAMP), ions, etc.
This quiz covers the different types of cell signaling molecules, including endocrine, paracrine, and autocrine ligands, as well as the stages of cell signaling, such as reception, transduction, and response.
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