week 5 Flashcards
define enzymes
catalyse a particular reaction, leaving the enzyme unchanged
define catabolic
breakdown
define anabolic
synthesis
example of anabolic reaction = acetylcholine
- Synthesis of acetylcholine (choline acetyltransferase)
- Acetylcholine is packaged in vesicle (the yellow) up to leave the axon
- Acetylcholine leaves the neuron & begin to cross the synapse
- Acetylcholine reaches the other side of the synapse & binds to the receptor causing the message to be sent
- After the message is sent, acetylcholine is released back into the synapse
- Acetylcholinesterase (enzyme) breaks down acetylcholine, inactivating it
irreversible inhibitors of Acetylcholinesterase & effect
- chemical warfare agents e.g., sarin gas
- insecticides e.g., parathion
= build up of acetylcholine = toxic
reversible inhibition of Acetylcholinesterase & effect
- donepezil = inhibits enzyme = increase drug in brain = helps with memory = helps with Alzheimer’s disease
- pyridostigmine
- rivastigmine
define false substrate
binds to enzymes but not actual substrate = disrupts normal metabolic pathway
what are the four superfamilies of receptors & fast to slowest & location
- ligand-gated ion channels (ionotrophic receptors) = cell membrane
- protein coupled receptors (metotrophic) = cell membrane
- kinase-linked receptors = cell membrane (some intracellular)
- nuclear receptors = intracellular (class I = cytoplasm, class II = nucleus)
define ligand
bind to receptor & can be antagonist
e.g., hormones, neurotransmitters, growth factors
example of ligand gated ion channel
nicotinic acetycholine receptor, GABA A, Nicotonic, NMDA receptors
example of receptor: ligand gated ion channel
nicotinic acetycholine receptor, GABA A, Nicotonic, NMDA receptors
example of ligand for: ligand gated ion channel & is it an agonist, antagonist or allosteric modulator
GABA, acetycholine, glutamate = agonist & benzodiazepines are allosteric modulators
what is the effector of each receptor superfamily
- ion channel
- enzymes & ion channels
- protein kinases
- gene transcription related molecules (e.g., transcription factors)
structure of ligand gated ion channel receptor
oligomeric (4-5 subunits) combined to form pore in the middle)
define coupling
is the effector & the receptor the same macromolecule
ligand gated ion channel: coupling?
direct - ion channel part of the receptor
example of receptor: G protein-coupled receptor
adenosine, adrenergic receptors
example of ligand: G-protein-coupled receptor & is it an agonist, antagonist or allosteric modulator
caffeine & adrenaline/noradrenaline
= every ligand agonist except caffeine which is an antagonist
structure of G-protein-coupled receptor
mono or oligomeric 7-TM with a G protein coupling site
G-protein-coupled receptor: coupling?
indirect - transducer = g protein & arrestin
what activates the effector in G protein coupled receptor
via G proteins or arrestins
what are the three subunits of a G-protein coupled receptor
alpha, beta, gamma = takes message from receptor to effector = transducer
- beta, gamma unit separates from alpha when binds & alpha activates effector depending on specific alpha type
three types of alpha subunits & what they do
Gas = stimulates = enzyme works better
Gai = inhibits enzymes
Gaq = increase calcium
main effector for Gas & Gai
Adenylyl cyclase (AC) = the enzyme responsible for the production of cAMP (second messenger) = intracellular signal induction
main effector for Gaq
phospholipase C = enzyme responsible for inositol triphosphate (IP3) & diacylglycerol (DAG) formation (they are second messengers)