Lecture 18 2/16/24

Question 1

What is the single parent precursor of hormones in the ACTH family?

Answer 1

POMC

Question 2

Which molecules are produced when POMC is split roughly in half?

Answer 2

-AACTH
-b-LPH

Question 3

What must occur in order for AACTH and b-LPH to be secreted?

Answer 3

the two molecules must be separated via hydrolysis and co-secreted by pituitary cells

Question 4

What can ACTH be hydrolyzed into?

Answer 4

-aMSH
-CLIP

Question 5

What can b-LPH be hydrolyzed into?

Answer 5

-y-LPH
-b-endorphin

Question 6

Which amino acids in ACTH are the most important and bioactive?

Answer 6

the first 24 AAs

Question 7

Why is it important that ACTH is measured via an antibody recognition site in the tail?

Answer 7

-mutated ACTH with a normal bioactive region and abnormal tail can be active in the animal without being detected via assay
-mutated ACTH with a normal tail but abnormal bioactive region can lead to signs of ACTH deficiency while producing normal assay results

Question 8

What are the potential roles of oxytocin?

Answer 8

-synthetic oxytocin used to reinforce contractions during birth process
-naturally produced oxytocin triggers milk ejection during breastfeeding

Question 9

What is the primary source of both oxytocin and ADH?

Answer 9

hypothalamus

Question 10

Which family is ADH classified into?

Answer 10

oxytocin family

Question 11

What is a receptor?

Answer 11

molecule on the cell surface or within the cell that recognizes and binds with ligands to produce some effect in the cells

Question 12

What are the characteristics that can vary between different receptors?

Answer 12

-specificity for hormone
-affinity
-saturability
-reversibility of binding
-specific response

Question 13

What are the characteristics of receptor specificity?

Answer 13

-often HIGH specificity for the hormone/ligand
-can have some overlap with very similar hormones

Question 14

What are the characteristics of the mineralocorticoid receptor (MR)?

Answer 14

-belongs to cytoplasmic/nuclear receptor family
-activated by mineralocorticoids and glucocorticoids
-protected from glucocorticoids via enzyme that converts cortisol into cortisone

Question 15

What are the characteristics of receptor affinity?

Answer 15

-strength by which hormone is bound to its receptor
-high affinity receptor requires less hormone to reach 50% receptor saturation

Question 16

How does affinity relate to concentration?

Answer 16

decreased concentration requires receptor to have increased affinity

Question 17

How does affinity relate to bioactivity?

Answer 17

increased affinity leads to increased bioactivity

Question 18

What are the characteristics of receptor saturability?

Answer 18

-number of receptors in a target cell can change by day, or even by minute
-receptor down-regulation leads to decreased target tissue responsiveness
-receptor up-regulation leads to increased target tissue responsiveness

Question 19

What can lead to receptor down-regulation?

Answer 19

-inactivation of receptor molecules
-inactivation of intracellular protein signaling molecules
-temporary sequestration of receptors
-destruction of receptors via lysosomes
-decreased receptor production

Question 20

What are the two types of hormone receptor models?

Answer 20

-plasma membrane receptors: bind hormones that cannot enter cell
-intracellular receptors: bind hormones that can freely enter cell

Question 21

What is signal transduction?

Answer 21

process involving the conversion of a signal from outside the cell to a functional change within the cell

Question 22

What is the pathway of signal transduction?

Answer 22

-first messenger + membrane receptor leads to series of reactions in cell membrane
-rxns release second messenger into cell
-second messenger leads to biological effect

Question 23

What are the 4 second messengers?

Answer 23

-cAMP
-IP3
-DAG
-Ca++

Question 24

What are the characteristics of intracellular hormone receptors?

Answer 24

-floating receptors
-called non-transformed when connected to molecular chaperones
-activated receptors move to DNA and bind
-binding leads to genomic effects
-no second messenger

Question 25

What are the characteristics of GABA?

Answer 25

-most important inhibitory molecule in brain
-synthesized starting from glutamic acid

Question 26

What is the role of vitamin B6 in GABA synthesis?

Answer 26

fundamental cofactor for synthesis and recycling back to glutamic acid

Question 27

What is the role of T4 in GABA synthesis?

Answer 27

-excess T4 binds and sequesters B6
-prevents GABA production due to lack of cofactor

Question 28

Which receptors recognize the catecholamines (epinephrine and norepinephrine)?

Answer 28

-alpha-1
-alpha-2
-beta-1
-beta-2

Question 29

Which response is associated with activation of the beta-1 receptor?

Answer 29

increased heart rate

Question 30

Which response is associated with activation of the beta-2 receptor?

Answer 30

increased glycogenolysis