Intracellular Signaling at the Cell Membrane Flashcards
(55 cards)
Receptors in the cell membrane are key in what 2 functions?
Detecting extracellular signals and modifying cell function based on those signals
What are the intracellular events that transform the extracellular signal into an intracellular signal?
Transduction
What do these events all involve?
-Source of some 2nd messengers
-Site where some 2nd messengers accumulate
-Site where ionic 2nd messengers are regulated
- Important site where regulatory proteins and enzymes localize and integrate signaling
The cell membrane
Describe the initial activation intracellular signaling model.
Ligand Binding: A signaling molecule (ligand) attaches to a cell membrane receptor.
Receptor Activation: This binding activates the receptor.
Intracellular Protein Activation: The activated receptor triggers an intracellular protein.
Second Messenger Production: This protein generates a second messenger.
Second Messenger Activation: The second messenger activates another protein.
Signaling Cascade: This protein sets off a series of reactions.
Cellular Effects: The cascade leads to cellular responses or changes.
What is an effector?
A cellular component that carries out specific actions in response to a signal.
What’s another name for the first messanger?
Lignan
Describe the deactivation of the intracellular signaling model.
Decreased First Messenger: When the concentration of the first messenger decreases,
Inactive Receptor: The cell membrane receptor is no longer activated.
Inactive Protein: The protein associated with the receptor becomes inactive.
Second Messenger Depletion: The protein or enzyme stops producing the second messenger.
Second Messenger Inactivation: Another mechanism reduces or inactivates the second messenger.
Ineffective Activation: With the low second messenger concentration, it can’t activate its target protein.
Inactive Effectors: Effectors are no longer activated.
What’s another term for deactivation?
Downregulation
Why does downregulation take place?
To prevent overstimulation or maintain a balance in cellular signaling.
What is the extracellular signal known as?
First messenger
What happens during receptor activation?
An increased cytosolic or membrane concentrations of a 2nd messenger
What is the process by which a relatively small initial signal or stimulus is greatly increased in magnitude or effect as it progresses through a signaling pathway
Amplification
What are 3 reasons for signal termination?
Inactivation of receptor (i.e. no 1st messenger) or receptor-associated effectors
degradation or removal of 2nd messenger
negative feedback
What are 3 types of cell membrane receptors?
1.) Ion channel-coupled receptors
2.) G-protein-coupled receptors
3.) Enzyme-coupled receptors
Which is the largest family of cell membrane receptors?
G-protein-coupled receptors (800)
Almost half of medications act on what receptors/pathways?
G-protein-coupled
What is a G-protein?
Guanine nucleotide
True or False. The activated G-protein will modify the activity of an enzyme.
True.
Does the activation G-protein have intrinsic GTP-ase activity? Or does it get its energy elsewhere?
Intrinsic
When GTP hydrolyzed
into GDP, what happens?
Then the G-protein is inactive
What are the 3 G-protein subunits?
alpha, betta, gamma
How are the g- protein subunits bound: Unstimulated?
α is bound to GDP, and βγ is bound to α
How are the g- protein subunits bound: Stimulated?
α subunit releases GDP, replacing it with GTP and the α subunit disengages from the βγ subunits
What happens when α unit hydrolyzes GTP into GDP?
It becomes inactivated again
