Lecture 13 & 14 Flashcards
Where are receptors located?
normally found on the cell surface and typically span across the cell membrane (transmembrane proteins)
Role of receptors?
There they act as recognition macromolecules allowing chemical detection and communication across the cell membrane
What is a ligand?
A chemical substance that binds to a receptor protein, In more generic terms a ligand is defined as a smaller molecule that binds to another larger molecule.
What are agonists?
Ligands that interact with a receptor to produce a measurable biological response (activates the receptor)
What are antagonists?
Ligands that interact with a receptor to block a biological response (equivalent to inhibitor of enzymes)
Agonists and antagonists in regards to drugs?
agonists are drugs that mimic endogenous messengers, whereas antagonists are drugs that block endogenous messengers
How is a receptor activated or inhibited?
A ligand must bind the receptor protein
What are the different types of ligands?
Ligands can be endogenous (produced in our body) or exogenous (not produced in the body but are introduced). Medicinal (or recreational) drugs and toxins are exogenous ligands.
process of ligand binding?
The ligand travels from its source to the receptor then binds (reception), the receptor protein undergoes conformation changes to which the ligand will become activated or inhibited depending on whether the lugand was an agonist or antagonist. This changes the cellular response.
What events follow activation ?
Signal transduction
What is signal transduction?
a chain of events where messages (in the
form of various molecules) are passed on through the cell, ultimately
leading to a cellular response
What prevents signal transduction for taking pace
Inhibition of a receptor prevents the signal transduction process from taking place, thereby inhibiting the cellular response.
Similarities between enzymes and receptors?
Both bind something
can both be membrane bound or free in the cytosol
Both show specificity (that is, the active site/ligand binding site and substrate/ligand are complementary to one another).
Both enzymes and receptors can be activated and inhibited and are extensively used as medicinal drug targets.
Differences between Enzymes and receptors?
An enzyme generally has a single active site where one substrate molecule binds. This substrate molecule is then changed into a product. In contrast, receptors may have one or multiple ligand binding sites. The ligand binds to activate or inhibit a cellular response, the ligand is then released unchanged.
What are four types of physiological receptors?
• Membrane proteins coupled to ion channels (known as ligand-gated ion channels)
• Membrane proteins coupled to G proteins (known as G-protein coupled receptors, or GPCRs for
short)
• Membrane proteins coupled to enzymes that phosphorylate, i.e. kinases (e.g., receptor tyrosine
kinase, RTK)
• Receptors that regulate gene expression (known as nuclear receptors)
