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Questions and Answers
What is a steroid?
An organic compound with four rings arranged in a specific molecular configuration.
The steroid core structure is composed of _____ carbon atoms, bonded in four 'fused' rings.
seventeen
Which ring structure is present in steroids?
Cholesterol is the only known steroid found in animals.
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What is the significance of the aromatic ring with C-3 OH in steroids?
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What is the role of modifications at the 16 and 17 positions in steroids?
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What are the common examples of estrogens?
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Match the steroid with its category:
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The side chain of steroids can be found at the _____ position.
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What is the significance of the six asymmetric carbon atoms in steroids?
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Steroids contain fatty acids.
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Study Notes
Steroids
- Steroids are organic compounds characterized by four rings arranged in a specific molecular configuration, known as the cyclopentanoperhydrophenanthrene nucleus.
- The four rings consist of three six-member cyclohexane rings (A, B, and C) and one five-member cyclopentane ring (D).
- Steroids are distinguished by the functional groups attached to this core structure and the oxidation state of the rings.
Numbering of Steroids
- The steroid core structure comprises 17 carbon atoms bonded in four fused rings.
- Angular methyl groups are typically found at C-10 and C-13 positions.
- An alkyl group may be present at C-17. Sterols typically have a hydroxyl group at C-3.
- A side chain is attached at the 17th position.
Properties of Steroids
- Steroids exhibit a relatively flat and rigid molecular structure.
- They possess high crystalline properties.
- Steroids are both hydrophilic and lipophilic.
- They do not contain fatty acids.
- Cholesterol, a well-known steroid, is exclusively found in animals.
SAR of Steroids
- The aromatic ring with a C-3 hydroxyl group is essential for activity.
- The 17β-hydroxyl group, maintaining a constant distance from the 3-OH, is crucial for activity.
- Unsaturation of ring B reduces activity.
- Modifications at the 16th and 17th positions can enhance activity.
Nomenclature of Steroids
- Steroids are primarily named as derivatives of basic steroidal ring systems.
- These ring systems are categorized based on the number of carbon atoms they contain:
- Gonane (C17):
- Estrane (C18): Examples include estrogens (estradiol, estrone, estriol).
- Androstane (C19): Examples include androgens (testosterone).
- Pregnane (C21): Examples include progesterone and corticosteroids.
- Cholane (C24): Examples include bile acids.
- Cholestane (C27): Examples include cholesterol.
Configuration of Steroids
- β Configuration: Substituents attached to the ring system from above are designated as β, with lines represented as thickened.
- α Configuration: Substituents attached to the ring system from below are designated as α, with lines represented as broken or dotted.
- Unknown Configuration: If the configuration of the substituent is unknown, it is represented with a wavy line.
Stereochemistry of Steroids
- The stereochemistry of the rings significantly influences the biological activity of specific steroid classes.
- The steroid nucleus contains six asymmetric carbon atoms (5, 8, 9, 10, 13, 14), potentially leading to 64 optically active forms.
- Steroids can exist in two conformations: chair form and boat form.
Notable Steroids:
-
Estrogens:
- Estrone
- Estradiol
- Estriol
- All derived from the Estrane ring system.
- C18
-
Androgens:
- Testosterone
- Derived from the Androstane ring system.
- C19
- Androst-4-en-17β-ol-3-one
-
Progesterone:
- Derived from the Pregnane ring system.
- C21
- Progest-4-en-3,20-dione
-
Cortisone:
- Derived from the Pregnane ring system.
- C21
- 17α,21-dihydroxypregn-4-en-3,11,20-trione
-
Bile acid-cholic acid:
- Derived from the Cholane ring system.
- C24
- 3,7,12-Trihydroxycholan-24-oic acid
-
Cholesterol:
- Derived from the Cholestane ring system.
- C27
- Choles-5-en-3β-ol
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Description
Test your knowledge about steroids, their structures, and properties. This quiz covers the chemical configuration, numbering of carbon atoms, and characteristics of steroids, including well-known examples like cholesterol. Perfect for students of biology and biochemistry!
