Term
| What is the most prominent common feature for hormones that are cholesterol derivatives? |
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Definition
| 3x 6 carbon rings bound to 1x 5 carbon ring |
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Term
| What are some of the differences between the cholesterol derivative hormones? |
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Definition
| Total number of carbons, side chains, saturated/unsaturated bonds |
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Term
| Describe the steps involved in prepping cholesterol esters for hormone biosynthesis |
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Definition
1. Start with cholesterol esters
2. CEH removes cholesterol from fatty acid linkages (gives free cholesterol)
3. Free cholesterol crosses membrane into mitochondria (StAR complex modulates this)
4. P450scc converts cholesterol to pregnenolone (considered the rate limiting step in steroid hormone biosynthesis)
NOTE: StAR also rate limits, but itsnt a biosynthetic step
Note: Hormones regulate all of these steps
5. Pregnenolone comes out of the mitochondria for further modification |
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Term
| What hormone does pregnenolone become in the zona glomerulosa? What enzymes are involved in its production? |
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Definition
1. Aldosterone
2. 21 hydroxylase (first) followed by 11-beta hydroxylase second |
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Term
| What hormone does pregnenolone become prominently in the zona fasciculata? What enzymes are involved in this? |
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Definition
1. Cortisol
2. 17 alpha hydroxylase (first), 21 hydroxylase (second), and 11-beta hydroxylase (third) |
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Term
| Describe the pathway for gonadocorticoid synthesis in the zona reticularis |
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Definition
1. Prenenolone becomes DHEA (dehydroepiandrosterone) via the activity of 17-alpha hydroxylase and then 17,20 lyase
2. DHEA becomes androstene 3,17 dione, which becomes testosterone
3. Testosterone becomes estradiol via aromatase (this happens in the gonads) |
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Term
| Explain the mechanism for how steroid hormones regulate protein synthesis |
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Definition
1. Steroid hormones enter cell and go into nucleus
2. Steroid hormones bind to specific receptors in target cells
3. The hormone/receptor complex has a specificity for a base pair sequence in DNA that it binds to
4. The binding of the complex to the DNA can either promote or inhibit transcription of genes, altering protein synthesis |
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Term
| What is RU 486 and how does it work? |
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Definition
An antihormone drug given to abort a pregnancy
It functions by competitively binding to the progesterone receptor, blocking its ability to regulate mRNA transcription. The inability of progesterone to function leads to an inability to maintain a pregnancy. |
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Term
| How do cells maintain the affinity of mineralocorticoids for their receptors when the receptors have an equal affinity for both mineralocorticoids and glucocortitoids? |
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Definition
Metabolism of glucocorticoids (cortisol into cortisone)
Note: Carbenoxolone can inhibit this reaction, leading to consitutive activation of mineralocorticoid receptors by glucocorticoids |
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Term
| What hormone converts testosterone to 5-alpha-dihydrotestosterone and what does this accomplish? |
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Definition
1. 5-alpha reductase
2. 5alpha-DHT has a higher affinity for receptors then normal testosterone, so this enzymes presence allows cells to respond to lower levels of the hormone |
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