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The Physiological Roles of Lipids: Steroid Hormones, Bile Salts, and Eicosanoids

This chapter explores the critical physiological roles of lipids, focusing on steroid hormones derived from cholesterol and their diverse functions in the body, including aldosterone and cortisol. It examines bile salts, which are oxidized cholesterol products that facilitate lipid digestion. Furthermore, the chapter delves into the significance of eicosanoids, such as prostaglandins and thromboxanes, which play crucial roles in inflammation and blood clotting, alongside the enzymes that mediate their synthesis. Essential for understanding lipid biology and metabolism.

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The Physiological Roles of Lipids: Steroid Hormones, Bile Salts, and Eicosanoids

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  1. Chapter 13 – Lipids13.10 – 13.12 By: Mackenzie Stuck & Carlie Strawser

  2. 13.10 What are some of the physiological roles of steroid hormones? • Cholesterol: Starting material for the synthesis of steroid hormones • Aliphatic side chain on the D ring is shortened • Removal of the six – carbon unit • Secondary alcohol group • Oxidized to a ketone • Progesterone: resulting molecule

  3. Adrenocorticoid Hormones • Product of Adrenal Glands • “Adjacent to the renal” • Two groups • Mineralocorticoids • Regulates concentration of ions • Glucocorticoids • Control carbohydrate metabolism • “Corticoid” • Indicates the secretion is the cortex of the gland

  4. Ex: Mineralocorticoids • Aldosterone • Enhances re-absorption of Na ions in the kidneys • Increases the loss of Potassium • Controls tissue swelling

  5. Ex: Glucocorticoids • Cortisol • Increases glucose and glycogen concentrations • Expense of other nutrients • Cortisone (ketone derivative) • Used to treat: • Inflammatory diseases • Rheumatoid arthritis • Bronchial asthma

  6. Sex Hormones • Testosterone (male) • Promotes normal growth of the male genital organs • Increased testosterone • Deep voice • Facial and body hair

  7. Estradiol • Synthesized from testosterone • Aromatization of the A ring • Regulates cyclic changes in the uterus and ovaries • Menstrual cycle • Increases the level of Estradiol • Luteinizing Hormone (LH) causes Ovulation • Prepare uterine lining for fertilization • No fertilization = decrease

  8. 13.11 What are bile salts? • Bile Salts • Oxidized products of cholesterol • 1st: cholesterol is oxidized to the trihydroxy derivative • 2nd: end of aliphatic chain is oxidized to the carboxylic acid • 3rd: forms an amide bond with an amino acid • Taurine • Sports drinks

  9. Physical properties of bile salts • Powerful detergents • 1 end • Strongly hydrophilic • Rest of the molecule • Largely hydrophobic • Can disperse dietary lipids • facilitates digestion • Similar to the action of soap on dirt • Remove bile salts in 2 ways • Break down products of cholesterol • Solubilize cholesterol

  10. 13.12 What are prostaglandins, Thromboxanes, and Leukotriens? • Prostaglandins • A group of fatty-acid-like substances • Discovered in the 1930’s by • Kurzrok • Leib • Ulf Von Euler • Named it thinking it came from prostate gland • Small amount in both sexes

  11. Cyclooxygenase (COX) • Catalyzing enzyme in the presence of arachidonic acid synthesized in the body creating prostaglandins • Two types • COX – 1 • PGE2 (Prostaglandin E group) • Carbonyl group at the 9th carbon • Lowers blood pressure • Used as a decongestant • Induces labor

  12. COX – 2 • Responsible for making prostaglandins • Occurs when inflammatory cells interact with resident cells because the tissue is injured

  13. Thromboxanes • A class of arachidonic acid • Drived from PGH2 • Has a cyclic acetal ring • induces platelet aggregation • thromboxanes A2 causes blood to clot more • NSAI in COX enzymes • can cause excessive bleeding

  14. THE END !!!!!!!!!!!!

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