1 - Intro

Question 1

What are the precursors of steroid hormones?

Answer 1

cholesterol

Question 2

Give an example of a hormones that would fit into the miscellaneous category of hormone?

Answer 2

thyroid hormones

Question 3

What are peptide hormones synthesised from?

Answer 3

prohormones - they are cleaved to generate the hormones

Question 4

Give an example of a protein/peptide hormones and its inactive precursor?

Answer 4

ACTH (adrenocorticotropic hormone)

prohormone= POMC

Question 5

Where is ACTH produced?

Answer 5

by the anterior pituitary

Question 6

All of the anterior pituitary hormones are _____

Answer 6

polypeptides

Question 7

Where do the amino acids come from that are used to synthesis protein/peptide hormones?

Answer 7

the blood supply

Question 8

Describe the synthesis of protein/polypeptide hormones

Answer 8

• the pro-hormone is transcribed from the DNA and the mRNA bind to the rER (where it is translated)
• the prohormone is endocytose by the Golgi, which adds enzymes to the vesicles containing the pro-hormone. These cleave the prohormone
• the Golgi ‘liberates’ the active hormone
• vesicles filled with the active hormones accumulate near the cell surface
• when a signal arrives—–> exocytosis and the hormones is released into the blood

Question 9

Give an example of a steroid hormone

Answer 9

cortisol

Question 10

steroid producing cells have lots of _____

Answer 10

fatty droplets

Question 11

Describe the synthesis of steroid hormones

Answer 11

• cholesterol is delivered to the cell (e.g. adrenal) by LDLs and is stored as Fatty Acid Esters
• esterase enzymes break down the fatty acids esters to liberate the cholesterol
• StAR proteins drove cholesterol into the mitochondria
• in the mitochondria, many enzymes convert the cholesterol into the steroid hormone of choice
• is is secreted into the cytoplasm and then the bloodstream

NOTE: the enzymes present in the cells determine the final steroid hormone product

Question 12

Where are most steroid hormones produced?

Answer 12

adrenal glands or gonads

Question 13

Why are steroid hormones not stored in cells (like protein hormones are)?

Answer 13

because they are very lipid soluble —–> ‘constitutive’ secretion

Question 14

Would an RNA synthesis inhibitor cause a greater reception in protein or steroid hormone production?

Answer 14

NOTE: it would reduce the rate of synthesis of both

BUT it would greatly reduce protein hormones production because it is preventing mRNA production, which is key in the production of proteins

in the steroid hormones, it would interfere with the cholesterol pathway, but would reduce the production of esterase and StAR proteins

Question 15

How are proteins/polypeptide hormones transported?

Answer 15

• secreted into the blood and travel unbound to the site of action
• stored in the tissues that produce them (in vesicles)
• they aren’t bound to any plasma protein, so are sensitive to enzymatic breakdown

Question 16

What are some features of polypeptide/protein hormones?

Answer 16

• very short half life (minutes)

- short acting effect

Question 17

How are steroid hormones transported?

Answer 17

(they are stored in the blood)

• majority bind to plasma proteins
• —-> ALBUMIN is the most common plasma protein - it can mop up a large amount of steroid hormones, but the interaction isn’t very specific
• —-> for each individual steroid hormone, there is a more specific plasma protein, which forms a much stronger binding
• small amount is free in the blood - ONLY FREE STEROID HORMONES CAN LEAVE THE BLOOD, if it bound to plasma protein, it is not leaving the bloodstream

Question 18

What hormones does ACTH stimulate the production of in cells?

Answer 18

cortisol

Question 19

What is the mechanism of action of ACTH (protein/polypeptide hormones)?

Answer 19

• hormone binds to protein (ACTH) receptor (usually G-coupled protein receptors)
• this activates adenylate cyclase
• increase cAMP production from ATP
• cAMP activates protein kinase A
• this phosphorylates esterase, which liberate cholesterol
• also phosphorylates StAR proteins (becoming activated) and allows cholesterol to move into the mitochondria
  (steroid hormone production)

Question 20

What is the mechanism of action of steroid hormones?

Answer 20

• free steroid hormones enter cells (diffusion) and bound to intracellular receptors
• translocate to the nucleus, and impact the rate of transcription

Question 21

The steroid hormone mechanism of action on the cell has an effect that is _____

Answer 21

slow, but powerful