6 overview hormonal mechanisms

Question 1

what is the first precursor molecule in peptide hormone synthesis? what does it signal for?

Answer 1

preprohormone

‘pre’- hydrophobic signal peptide on N terminus: signals for further processing and packaging for exocytosis

Question 2

what happens in post translational modification in peptide hormone synth?

Answer 2

protein folding, disulphide bonds, glycosylation, pre-signal cleavage

Question 3

when does post translational modification happen?

Answer 3

whilst preprohormone transverses rER

Question 4

how is the protein transported from RER to golgi?

Answer 4

via microvesicles

Question 5

what type of hormone is in the golgi?

Answer 5

prohormone

Question 6

what happens to the prohormone in golgi?

Answer 6

additional processing, further cleavage, packaging into secretory granules

Question 7

what does the rate of peptide hormone release depend on?

Answer 7

rate of exocytosis

Question 8

when is the peptide hormone released?

Answer 8

upon arrival of stimulus

Question 9

what type of enzyme converts cholesterol into steroid hormones?

Answer 9

biosynthetic enzymes

Question 10

what property does cholesterol have and what is the consequence of this?

Answer 10

lipophilic, can diffuse through lipid bilayer so no secretory granules needed-> hormone is not stored

Question 11

what do steroid hormones bind to?

Answer 11

plasma carrying protein by weak reversible bonds because they are hydrophobic so are insoluble

Question 12

how do you increase levels of steroid hormones?

Answer 12

by increasing level of synthesis

Question 13

t1/2 of peptide vs steroid hormones

Answer 13

peptide: minutes
steroid: hours- days

Question 14

what are peptide hormones susceptible to?

Answer 14

protease enzymes because they are free hormone

Question 15

describe peptide hormone action

Answer 15

receptor molecules (cannot cross lipid bilayer) -> G protein and effector or tyrosine kinase
leading to signal transduction 
physiological response- altered activity of enzymes or ion channels/ altered expression of proteins

Question 16

describe steroid hormone action

Answer 16

intracellular receptors (and plasma membrane receptors)
-act as hormone regulated transcription factors
hormone-> cytosolic receptor-> nucleus
hormone -> nuclear receptor

acts on DNA to increase of decrease gene expression-> mRNA-> proteins and biological effects

Question 17

what metabolises hormones?

Answer 17

mostly enzymes in liver, kidney and blood
small prop by target tissues
excreted in urine/ faeces

Question 18

regulation of hormone release

Answer 18

1. feedback
2. neuroendocrine reflexes- input from higher centres
3. diurnal or circadian rhythm

Question 19

what is the typical diurnal variation of plasma cortisol?

Answer 19

peak in early morning, trough in late evening