lecture 13 - protein activation & inhibition 1 Flashcards
What are some common compounds that may inhibit or activate proteins?
hormones, neurotransmitters, drugs, toxins, poisons
What are the common steps in protein activation or inhibition?
Substance travels from source, binds to protein, activation/inhibition, changes to cellular response due to functional change
What are protein receptors?
Cellular proteins that control chemical signalling between and within cells
What is the difference between enzymes and receptors in terms of active sites?
Enzymes generally have 1, while receptors can have several
What is the difference between enzymes and receptors in terms of what they bind?
Enzymes bind substrates while receptors bind ligands
What is the difference between enzymes and receptors in terms of release of the bound substance?
Enzymes change substrate into product, while receptors release ligands unchanged
Where are receptors and enzymes found in a cell?
Membrane bound or free in cytosol
What are the 3 main classes of receptor?
Ligand-gated ion channels, G Protein Coupled Receptors (GPCR), Receptor tyrosine Kinase (RTK)
What is the name for a chemical that binds to a receptor?
A ligand
Where are endogenous ligands produced?
Inside the body
Where are exogenous ligands produced?
Outside the body, e.g. drugs and toxins
What are the 3 types of receptor signalling used by locally-produced chemical substances?
Synaptic, paracrine, autocrine
What type of receptor signalling is used by chemical substances produced at a distant site to the receptor (i.e. hormones)?
Endocrine
What is synaptic signalling?
The presynaptic cell produces a chemical that is received by a specific post-synaptic cell that expresses the receptor
What is paracrine signalling?
A cell produces a chemical that is received by receptors on a number of neighbouring cells
What is autocrine signalling?
A cell excretes a chemical that is received by receptors expressed on the same cell
What is endocrine signalling?
A cell produces a chemical, it is transported via the blood stream, and is received by a distant cell expressing the appropriate receptor
Where are the majority of receptors found, and why?
The outer cell membrane, so they can act as sensors of the extracellular environment without the ligands having to pass into the cell
What is ligand specificity?
Receptors and ligands have specificity, so only certain ligands match the corresponding receptor’s binding pocket
What is the name for a ligand that is able to bind to and activate a receptor?
An agonist
How do agonists activate receptors?
They bind, the receptors undergoes a conformational change
What happens when a membrane receptor has been a activated by an agonist ligand?
Active receptor starts a chain of events where messengers are passed on thorough the cell via signal transduction
What is the name for a ligand that binds to a receptors and prevents activation by an agonist?
Antagonist
What is an antagonist ligand?
A ligand that binds to a receptor and blocks agonist binding to inhibit signal transduction
What is the signal transduction mechanism of adrenaline in the lungs?
Adrenaline acts as an agonist to activate the B-adrenergic receptor (GPCR), resulting in signal transduction that causes bronchodilation
What is the signal transduction mechanism of insulin?
Insulin acts as an agonist to activate an insulin receptor (a RTK), resulting in signal transduction and then glucose uptake
What receptor does adrenaline act on to cause bronchodilation?
beta-adrenergic (a GPCR)
What type of receptor is beta-adrenergic
GPCR
What receptor does insulin act on to increase glucose uptake?
Insulin receptor
What type of receptor is an insulin receptor?
RTK receptor
