hormones and receptors

Question 1

Three categories of hormones

Answer 1

1) derivatives of tyrosine, 2) derivatives of cholesterol (steroids), and 3) peptides and proteins

Question 2

list Tyrosine derived hormones

Answer 2

epinephrine, norepinephrine, dopamine and thyroxine

Question 3

List steroid hormones

Answer 3

testosterone, cortisol, estrogen, aldosterone, Vitamin D, progesterone

Question 4

list peptide hormones

Answer 4

oxytocin, vasopressin, angiotensin, thyrotropin releasing hormone, GnRH

Question 5

List protein hormones

Answer 5

insulin, glucagon, growth hormone, ACTH, prolactin, TSH

Question 6

synthesis/secretion of peptide and protein hormones

Answer 6

pro-hormone synthesized on ribosomes > targeted to ER > presequence is cleaved > prohormone transported to golgi >processed and packaged in secretory vesicles > secretion via vesicular exocytosis (Ca dependent)

Question 7

synthesis/secretion of catecholamines

Answer 7

pro-hormone synthesized on ribosomes > targeted to ER > presequence is cleaved > prohormone transported to golgi >processed and packaged in secretory vesicles > secretion via vesicular exocytosis (Ca dependent)

Question 8

Why is the half life of peptide/protein hormones limited

Answer 8

The blood contains many proteases

Question 9

Which peptide/protein hormones are NOT transported in blood as free hormones

Answer 9

growth hormone, prolactin and Insulin-like growth factor

Question 10

precursor for all steroid hormones

Answer 10

cholesterol

Question 11

How do steroid hormones differ from peptide hormones

Answer 11

1. They are lipophilic and membrane permeant, so they are not secreted via vesicular exocytosis. 2. Steroids are not stored in the cell which synthesizes them, so they are immediately released into blood stream. 3. steroids Must be carried by carrier proteins in blood. 4. Steroids have much longer half lives (hours to days) so they linger in blood stream for long time

Question 12

What proportion of steroid hormone exist in free forms

Answer 12

1-5% The rest is bound to carrier proteins.

Question 13

Which form of steroid hormones is active

Answer 13

free form only

Question 14

describe two ways of measuring hormone levels

Answer 14

1. bioassays: hormone function is measured by using an exogenous system e.g. cell lines, to measure hormone activity. 2. immunoassays: Radio-immunoassays (RIA) and enzyme linked immunosorbent assays (ELISA) measure antibody binding to a specific region of the hormone

Question 15

epinephrine/NE action at target organ

Answer 15

Bind to G-protein receptors > changes intracellular second messengers (cAMP, DAG, IP3, etc)

Question 16

Which hormones bind to JAK/STAT receptors

Answer 16

growth hormone and prolactin

Question 17

Function of JAK/STAT receptors

Answer 17

Binding to these receptors results in coupling and activation of a tyrosine kinase (Janus kinase or JAK), which then causes the phosphorylation of a group of proteins called signal transducers and activators of transcription (STATs).

Question 18

which hormones bind to tyrosine kinase receptors

Answer 18

insulin and IGF-1

Question 19

List steps in steroid receptor activation

Answer 19

steroid hormone enters cell and binds to receptor in cytosol or nucleus. The receptor-hormone complexes then bind to specific hormone responsive elements (HRE) and activate transcription of specific genes

Question 20

How is hormone secretion regulated

Answer 20

Via feedback loops which keep levels regulated around a specific set point.

Question 21

give example of a positive feedback loop

Answer 21

oxytocin release during labor