1.5 Steroids Flashcards
Steroids are derived from…
Cholesterol
Which organelle are steroids produced in? Which protein does this depend on?
- Made in mitochondria
- Steroid acute regulatory protein (STAR)
List the three layers of the adrenal cortex and the type of steroid hormone produced in each
- Zona glomerulosa (outside): mineralocorticoid
- Zona fasciculata (middle): glucocorticoid
- Zona reticularis (inside): androgen
What is meant by tissue dependent synthesis/modification?
- Steroids are produced via enzyme-dependent pathways
- (Every steroid in a pathway is produced, as if some traffic is clicking off)
- Since different tissues have different enzymes, this means that different tissues produce/modify steroids differently
How are steroid hormones carried through the blood? What are the advantages of this?
- Carried through the blood on binding proteins
- Bond needs to be weak enough to allow dissociation at site
- Protects against precipitation, renal filtration, and enzyme attack
- Also provides a buffer in cases sudden change in concentration
True or false: target cells cannot bind to proteins while they are attached to binding proteins. The hormone must first dissociate with the target protein.
True
What are the three glands of the body at which steroids are produced?
- Adrenals
- Gonads (ovaries/testes)
- Placenta, during pregnancy
Thyroid hormones are not steroid hormones. Why, then are they still carried through the blood on carrier proteins?
- Because they have large, hydrophobic structures; will precipitate in plasma
- So the carrier protein ensures this does not happen
How does deiodination of T4 into T3/rT3 affect its function?
Into T3: increased activity
Intro rT3: Inactivated
What is the relationship between the affinity of different hormone carrier proteins and hormone receptors?
- Receptors must have higher affinity
- This is what enables hormones to detach from CP, and bind to receptor, exerting effect
