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Questions and Answers
Which hormones are primarily produced in the Leydig cells of the testis?
What is the most active form of estrogen?
How many carbon atoms are present in glucocorticoids?
Which of the following hormones is associated with the development of female sex organs?
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What is one of the primary functions of glucocorticoids?
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Which hormone is primarily responsible for preparing the uterus for implantation?
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Which hormone is NOT produced by the adrenal cortex?
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What effect do mineralocorticoids have on the body?
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What are derived lipids primarily characterized by?
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Which of the following compounds are classified as derived lipids?
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Which component is a part of the steroid nucleus structure?
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What is the primary function of cholesterol in the body?
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What is the typical cholesterol level considered normal in blood?
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Which of the following statements about cholesterol transport in the body is true?
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What is a significant consequence of hypercholesterolemia?
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What is the primary site for the synthesis of Vitamin D3?
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What is one of the main functions of bile salts?
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What type of acid is primarily formed from cholesterol in the liver?
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Which of these compounds is a product of bile acids combined with glycine?
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What type of lipid is involved in the treatment of arrhythmias and congestive heart failure?
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What is formed when bile acids combine with taurine?
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How do primary bile acids become secondary bile acids?
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What is the primary role of testosterone in males?
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What is the chemical structure characteristic in the hormones secreted by the adrenal cortex?
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Mineralocorticoids primarily aid in which of the following processes?
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What type of biological function do glucocorticoids primarily have?
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What effect does 11-Deoxycorticosterone (DOC) primarily have?
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How many carbon atoms are present in ergosterol?
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Which of the following statements about the absorption of cholesterol is true?
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What percentage of cholesterol in the body is carried by LDL?
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What is the main function of cholesterol in the body, aside from serving as a precursor for steroid hormones?
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Which statement correctly describes hypercholesterolemia?
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Which condition is cholesterol level most directly associated with?
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What is the primary site for the activation of Vitamin D2?
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What is one of the functions of bile salts?
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Which compound acts as a cardiac glycoside used in treating arrhythmias?
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How are secondary bile acids primarily formed from primary bile acids?
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What happens when bile acids combine with taurine?
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Study Notes
Derived Lipids
- Derived lipids are produced by the hydrolysis of simple and compound lipids.
- These lipids are also related to fatty acids.
- Examples include alcohols like glycerol and steroids.
Steroids
- Steroids contain a steroid nucleus which consists of 3 cyclohexane rings (A, B, and C) and 1 cyclopentane ring (D).
- These rings are fused together.
Cholesterol
- Cholesterol is a steroid primarily found in animal sources.
- Cholesterol plays a crucial role in the structure of all body cells, and is a precursor to steroid hormones and bile acids.
- Cholesterol is absorbed easily by the body.
Ergosterol
- Ergosterol is a steroid found in plants.
- It has a similar structure to cholesterol but contains 28 carbon atoms.
- Ergosterol is poorly absorbed and primarily functions as a precursor to vitamin D2.
Cholesterol in the Blood
- The normal blood cholesterol level is less than 200 mg/dl.
- High cholesterol levels (hypercholesterolemia) are associated with atherosclerosis, myocardial infarction, and cerebral stroke.
- 75% of cholesterol is carried in LDL, while 25% is carried in HDL.
Cholesterol Occurrence
- Cholesterol is found in various body tissues, with the highest concentrations in the brain, liver, skin, small intestine, and adrenal cortex.
- There are two forms of cholesterol: free cholesterol and cholesterol esters.
- Cholesterol esters typically make up 70% of cholesterol, and they are linked to fatty acids on the OH group of C3.
Steroid Hormones
- Steroid hormones are derived from cholesterol.
- They play vital roles in the body, including regulating reproduction, metabolism, and stress response.
Male Sex Hormones
- Testosterone is the primary male sex hormone, and it is produced by the Leydig cells of the testes.
- Testosterone is involved in the development of male sex organs and secondary sex characteristics.
- It also stimulates spermatogenesis and has strong anabolic effects.
Female Sex Hormones
- Estrogen and Progesterone are the primary female sex hormones, produced by the ovaries and placenta.
- Estrogen stimulates the development of female sex organs and secondary sex characteristics.
- It also prepares the uterus for the implantation of an ovum, and has anabolic effects.
- Progesterone is crucial for preparing the uterus for the implantation of a fertilized ovum, and it is known as the "hormone of pregnancy".
Adrenal Cortex Hormones
- The adrenal cortex hormones are produced by the adrenal glands and include glucocorticoids and mineralocorticoids.
Glucocorticoids
- Glucocorticoids, like cortisol, are primarily involved in regulating carbohydrate metabolism.
- They increase blood glucose levels and suppress inflammatory and allergic responses.
Mineralocorticoids
- Mineralocorticoids, like aldosterone, regulate electrolyte balance, primarily by promoting sodium retention and potassium excretion.
Vitamin D
- Vitamin D is a steroid hormone involved in calcium metabolism.
- Vitamin D3 is produced from 7-dehydrocholesterol by exposure to ultraviolet radiation in the skin.
- Vitamin D2 is synthesized from ergosterol by ultraviolet radiation.
- Vitamin D is activated in the liver and kidney, and it increases calcium absorption from the gastrointestinal tract, promoting bone ossification.
Bile Acids
- Bile acids are synthesized from cholesterol in the liver and used for the digestion and absorption of lipids.
- Primary bile acids, Cholic acid and Chenodeoxycholic acid, are synthesized in the liver.
- Secondary bile acids, Lithocholic acid and Deoxycholic acid, are formed by the action of intestinal bacteria on primary bile acids.
Bile Salts
- Bile acids conjugate with glycine or taurine to form bile salts.
- These bile salts then bind with sodium or potassium to form sodium or potassium glycocholate or taurocholate.
Functions of Bile Salts
- Bile salts aid in the digestion and absorption of lipids in the intestines.
Cardiac Glycosides
- Cardiac glycosides, like digitalis, are steroid derivatives.
- They are used clinically to treat arrhythmias and congestive heart failure.
Derived Lipids
- Derived lipids are substances originated from simple lipids and compound lipids by hydrolysis or related to lipids.
- Examples of derived lipids include alcohols (glycerol), steroids, and fatty acids.
- Steroids are compounds with a characteristic structure containing three cyclohexane rings (A, B, and C) and one cyclopentane ring (D) fused together.
Cholesterol
- Cholesterol is a type of steroid found in animal sources.
- Humans can absorb cholesterol readily, while plants have a poorly absorbable version called ergosterol.
- Cholesterol plays a crucial role in the structure of all body cells, and is a precursor for steroid hormones and bile acids.
- Cholesterol levels in the blood can be elevated, which is associated with atherosclerosis, heart attacks, and stroke.
- Cholesterol is transported in the blood primarily as LDL (low-density lipoprotein) and HDL (high-density lipoprotein).
- Cholesterol is found in the largest amounts in the brain, liver, skin, small intestine, and adrenal cortex.
Steroid Hormone Types
- Male sex hormone: Testosterone, with 19 carbon atoms, is produced in the Leydig cells of the testes. It plays a role in the development of male sex organs, secondary male sex characteristics, spermatogenesis, and has a strong anabolic effect.
- Female sex hormones: Estrogen (18 carbon atoms) and progesterone (21 carbon atoms) are produced in the ovaries and placenta. Estrogen is involved in the development of female sex organs, secondary female sex characteristics, and has an anabolic effect. Progesterone prepares the uterus for implantation of the fertilized egg, and is a hormone of pregnancy.
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Adrenal cortex hormones: Include glucocorticoids (21 carbon atoms) and mineralocorticoids (21 carbon atoms).
- Glucocorticoids such as cortisol increase blood glucose levels (hyperglycemic), suppress immune and inflammatory responses, and are involved in allergic responses.
- Mineralocorticoids such as aldosterone promote sodium retention and potassium excretion by the kidneys, and are involved in sodium and chloride reabsorption and potassium reabsorption.
Vitamin D
- Vitamin D3 is synthesized in the skin from 7-dehydrocholesterol by exposure to ultraviolet (UV) rays.
- Vitamin D2 is synthesized from ergosterol by UV rays.
- Both vitamin D3 and D2 require activation in the liver and kidney.
- Vitamin D increases calcium absorption from the gastrointestinal tract and promotes bone ossification.
Bile Acids
- Bile acids are formed from cholesterol in the liver.
- Primary bile acids include cholic acid and chenodeoxycholic acid.
- Secondary bile acids are formed by the action of intestinal bacteria on primary bile acids. Examples include lithocholic acid and deoxycholic acid.
- Bile acids unite with glycine (forming glycocholic acid) or taurine (forming taurocholic acid).
- Glycocholic acid or taurocholic acid, in turn, forms bile salts when combined with sodium or potassium.
Functions of Bile Salts
- Assist in lipid digestion.
- Assist in lipid absorption.
Cardiac Glycosides
- Cardiac glycosides are composed of a steroid structure coupled with a sugar (glucose or galactose).
- Digitalis, a type of cardiac glycoside, is a potent cardiac stimulant widely used in the treatment of arrhythmias and congestive heart failure.
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