Cell Communication Flashcards
Which chemical messengers are amino acids?
The G’s:
Glycine
Glutamate
GABA
(And also aspartate)
Which chemical messengers are biogenic amines?
Dopamine
NE
Epi
Serotonin
Histamine
Which chemical messengers are choline esters?
Acetylcholine
Are T3 and T4 polar or nonpolar?
Polar. Hydrophilic.
Do hydrophilic chemical messengers cross the cell membrane?
Not on their own. They have to bind to cell surface receptors.
Which chemical messengers are nonpolar?
Lipophilic:
Steroids
Eicosanoids
Vit D/Retinoids
List three Eicosanoids
Prostaglandins
Leukotrienes
Thromboxanes
Do steroids cross the cell membrane?
Yes
They bind to receptors in the cytoplasm or nucleus of the target cells
Do Eicosanoids cross the cell membrane?
They usually bind to cell surface receptors
Dopamine, epi, and NE are derived from which amino acid?
Tyrosine
There are three components to all GPCRs:
- A plasma membrane receptor with seven transmembrane segments
- A G protein
- An effector (usually an enzyme) that generates an intracellular second messenger
Describe a GPCR in the inactive state
The alpha subunit is bound to GDP
Describe a GPCR in the active state
The alpha subunit releases GDP and binds to GTP
Name two contagious diseases that alter GPCRs
Cholera (inhibits GTPase activity in Gs subunits)
Pertussis (overactivation of Gs)
Which G protein subunit contains the intrinsic GTPase activity?
The alpha subunit
What are the three downstream effectors that GPCRs target?
Adenylyl Cyclase
Phospholipase C
Phospholipase A2
Which downstream effector leads to cAMP production?
Adenylyl Cyclase
Which downstream effector leads to IP3 and DAG?
Phospholipase C
Which downstream effectors leads to Eicosanoids?
Phospholipase A2
Effector enzymes always end in _____
ase
What is the function of Adenylyl Cyclase?
Gs: cAMP is increased
Gi: cAMP is decreased
What is the function of Phospholipase C?
Converts PIP2 into IP3 and DAG
IP3 increased intracellular Ca
DAG acts as a docking site for and activator of PKC
What is the function of Phospholipase A2?
Calcium dependent enzyme that liberates arachidonic acid from the cell membrane, allowing production of Eicosanoids
What is the effect of cAMP in myocytes?
increased contractility
What is the effect of cAMP in smooth muscle?
causes relaxation and dilation
What is the effect of cAMP on platelets?
increased aggregation
_____ activates PKA
cAMP
______ activates PKC
DAG
______ causes ionized calcium release
IP3
What is the role of kinases?
They add a phosphate group to a substrate
There are two types of synapses:
- Electrical
- Chemical
At electrical synapses, cells are connected by _______
gap junctions
Receptors at chemical synapses are either ______ or _______
Ionotropic (ion channels)
Metabotropic (GPCRs)
How wide is the synaptic cleft?
20-40 nm
In order for cellular excitation to occur, _______ influx or _____ efflux occurs
Sodium or calcium have to move into the cell
OR the amount of K leaving the cell has to decrease
In order for cellular inhibition to occur, which ions must alter?
Either increased K efflux out of the cell
OR increase CL influx
OR closure of Ca channels
Muscarinic receptors are __________
M is for Metabotropic (GPCR)
Nicotinic receptors are __________
Ionotropic (ion gated)
Where does Ach act as a neurotransmitter?
- Neuromuscular Junction
- Autonomic Ganglia
- Postganglionic PNS
- Sweat glands
Where does Ach synthesis occur?
Presynaptic nerve terminals
What is the rate limiting factor in Ach production?
Choline and Acetyl CoA
Why does Mg cause muscle weakness?
It is an antagonist of Ca at the presynaptic terminal, meaning it inhibits ACh release
Where are Nicotinic M receptors found? How do they function?
M is for muscle
They’re found at the NMJ
Increase Na influx
Where are nicotinic N receptors found?
Everywhere besides the NMJ
Which muscarinic receptors are Gi coupled?
All of the even ones (M2 and M4)
Makes sense because they’re both suppressive: M2 is cardiosuppressive, M4 suppresses presynaptic Ach release
Which muscarinic receptors are Gq coupled?
All of the odd ones (M1, M3, M5)
All of them are IP3 + DAG Ca
What is glutamate?
The primary excitatory neurotransmitter in the brain
What is GABA?
The primary inhibitory neurotransmitter in the brain
What is glycine?
The primary inhibitory neurotransmitter in the SPINAL CORD and lower brainstem
There are three ionotropic glutamate recceptors:
NMDA
AMPA
Kainate
What must occur for an NMDA receptor to be activated?
2 glutamate
2 glycine
AND
a depolarizing voltage change
Where does ketamine bind to NMDA receptors?
What is excitotoxicity?
Neuronal injury from unchecked glutamate release or inhibition
Which GABA receptors are metabotropic?
GABA B
Which GABA receptors are ionotropic?
GABA A
What kind of receptors are GABA A receptors?
Ligand gated Cl channels
Degradation of NE and Epi is carried out by two enzymes:
MAO
COMT
What is the end product of catecholamine degradation?
Vanillylmandelic Acid
Serotonin is synthesized from ________
tryptophan
Histamine is synthesized from ________
Hystadine
There is only one metabotropic amine neurotransmitter receptor:
5-HT3
How is pheochromocytoma detected?
By measure levels of vanillylmandelic acid in the urine
What is hydroxylation?
Addition of an -OH group
What is Carboxylation?
Removal of a CO2 group
Where is the largest concentration of dopamine receptors located?
Substantia Nigra
What are the main purine neurotransmitters?
ATP
ADP
Adenosine
What are the main roles of Adenosine?
- Signals cell injury
- Promotes sleep
- Induces platelet aggregation
What is the largest family of enzyme-linked receptors?
Tyrosine Kinases
What are the characteristics of cellular necrosis?
Cells Swell
Plasma Membranes Dissolve
Adjacent tissues undergo inflammation
What are the characteristics of cellular apoptosis?
Cells shrink
Plasma membranes remain intact
No inflammation in adjacent tissues
