Lecture 15- Endocrine System Pt 2 Flashcards
What three concepts go hand and hand in hormone-receptor binding?
- Law of Mass Action
- Specificity and Affinity
- Concept of K-D (Dissociation constant)
What is the Law of Mass Action?
[H]+[R]=[HR]
Hormone+Receptor=
Hormone Receptor Complex
What does a higher affinity lead to in the Law of Mass Action?
Higher affinity means more stickiness so, less likely for HR Complex to come apart
How are association and dissociation related in the Law of Mass Action?
Inversely related
What is the dissociation constant K-D?
Concentration of hormone where 1/2 of receptors are occupied
K-D=[H][R]/[HR]
How does a low K-D value affect hormone concentration?
When K-D is low it doesn’t require a very high hormone concentration to bind at least 1/2 of the receptors
High affinity=low concentration
What are four types of hormone/receptor alterations that can happen from phosphorylation?
- Secretory activity via exo/endocytosis
- Enzyme activity
- Ion channel activity
- Gene expression and protein synthesis
What are the major steps in G-Protein Coupled receptors?
- Hormone binds to 7-pass transmembrane protein
- TMP changes shape when hormone binds and becomes binding site for GTP
- G-alpha GDP becomes GTP
- Adenylyl Cyclase converts ATP to cAMP
- cAMP activates Protein Kinase A (PKA)
- PKA leads to phosphorylation
Why are G-alpha-s and G-alpha-i important for G-protein coupled receptors?
Regulate phosphorylation by creating or reducing cAMP
What are the three heterotrimeric GTP binding proteins?
G-alpha, G-Beta, G-Gamma
What do G-alpa-s, G-alpha-i, and G-alpha-q stand for?
G-a-s: stimulator
G-a-i: inhibitory
G-a-q: releases calcium
What subunits does GTP alpha have?
G-alpa-s, G-alpha-i, and G-alpha-q
What is the main enzyme in play for G-alpa-s and G-alpha-i?
Adenylyl Cyclase
Turned on by G-a-s/turned off by G-a-i
What does cAMP alter?
Phosphorylation which affects protein function
What is the role of G-alpa-s?
Activates Adenylyl Cyclase
