Hormone Receptor Interactions Flashcards
(20 cards)
What are the principles of hormone-receptor binding?
Receptor exhibits affinity for a hormone, hormone-receptor interactions are specific, a hormone may bind to more than one receptor, receptor number can vary, hormone signaling must be inactivated
What does the dissociation constant (Kd) define?
The strength of binding (affinity) between a hormone and receptor
Why must a hormone receptor have high affinity and specificity?
Hormones circulate in very low concentrations (10-7 to 10-12 M) to produce a biologic response
What are the three components in any system containing hormones and receptors?
- Free hormone (H)
- Free receptor (R)
- Hormone-Receptor complex (HR)
What does a lower dissociation constant (Kd) indicate?
A higher affinity of the receptor for the hormone
What is Kd a measure of?
Affinity between hormone and receptor
What is the significance of Kd in terms of receptor binding?
Kd is the concentration of hormone at which one-half of the available receptors are bound to hormone
What are agonists and antagonists in hormone-receptor interactions?
- Agonists: bind to and activate receptors
- Antagonists: bind but do not activate and prevent binding of natural hormone or ligand
Can a hormone bind to more than one receptor?
Yes, but with different affinity
What is up-regulation in hormone receptor dynamics?
Target cells can form more receptors in response to decreasing blood levels of a particular hormone
What happens during down-regulation?
Prolonged exposure to high hormone concentrations decreases receptor numbers in target cells
What are the types of interactions that hormones can have at target cells?
- Additivity
- Synergism
- Permissiveness
- Antagonism
What is synergism in hormone interactions?
Combined effect of hormones that is greater than the sum of their individual effects
What is permissiveness in hormone interactions?
One hormone affects the capacity of cells to respond to another hormone
What is antagonism in hormone interactions?
Hormones can diminish the effect of each other
What is a competitive antagonist?
A hormone that binds to the receptor but does not activate it
What is a functional (physiological) antagonist?
Hormones that have opposing physiological actions through different receptors
What is an example of physiological antagonism?
Glucagon and GH increase blood glucose, while insulin decreases it
Fill in the blank: Hormones interact with receptors in a ______ way.
specific
Fill in the blank: The hormone-binding site of a receptor has a particular ______.
shape
