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Questions and Answers
Which molecule is the starting material for adrenal steroidogenesis?
What is the role of StAR protein in adrenal steroidogenesis?
Which enzyme is responsible for cleaving cholesterol into pregnenolone and isocaproaldehyde?
Which hormones stimulate the secretion of mineralocorticoids?
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What is considered the rate-limiting step of adrenal steroidogenesis?
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Where does pregnenolone synthesis take place in adrenal steroidogenesis?
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Study Notes
Adrenal Steroidogenesis
- Adrenal steroid hormones are synthesized from cholesterol.
- Cholesterol in the adrenal cortex is stored in the esterified form in cytoplasmic lipid droplets.
- Stimulation of the adrenal cortex by ACTH, angiotensin II, and III activates esterase enzyme.
- Esterase enzyme converts cholesterol ester into free cholesterol.
- Free cholesterol is then transported into the mitochondria.
- In the mitochondria, cytochrome P450 side chain cleavage enzyme (P450scc) cleaves cholesterol into pregnenolone and isocaproaldehyde.
- This cleavage occurs between C22 and C20, resulting in pregnenolone (21-carbons) and isocaproaldehyde (6-carbons).
- ACTH or angiotensin II and III dependent steroidogenic acute regulatory (StAR) protein is essential for transporting free cholesterol from cytoplasmic lipid droplets to P450scc in the mitochondria.
- This step is considered as a rate-limiting step of adrenal steroidogenesis.
- Pregnenolone is a common precursor of all steroid hormones.
- Pregnenolone leaves the mitochondria and enters the smooth endoplasmic reticulum.
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Description
Learn about the process of adrenal steroid hormone synthesis from cholesterol in the adrenal cortex, including the role of ACTH and enzymes.
