Biochemistry Prelab Exercises

BCH2022- WEEK 11 PRECLASS EXERCISE

What is the mechanism of action and biological actions of?

1. Testosterone:

• Androgen, synthesised in the testes
• Synthesis involves cytochrome p-450 enzymes that cleave the side chain of cholesterol and introduce oxygen atoms
• Affect sexual development, sexual behaviour, and a variety of other reproductive and non-reproductive functions
• Travels to target cells through the blood stream, bound to carrier proteins, they act through nuclear receptors to change the level of expression of specific genes.

1. Luteinising hormone:

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1. Follicle stimulating hormone:

• Follicle-stimulating hormone (FSH) is a glycoprotein hormone found in humans and other animals.
• It is synthesized and secreted by gonadotropes of the anterior pituitary gland.
• Regulates the development, growth, pubertal maturation, and reproductive processes of the body.
• FSH and luteinizing hormone (LH) act synergistically in reproduction.

1. Cortisol:

• A steroid hormone, a major glucocorticoid produced by the adrenal cortex.
• It is released in response to biological and environmental stressors such as low blood glucose levels or public speaking.
• Presence of cortisol in the blood maintains concentrations of the key liver and adipose tissue enzymes required for gluconeogenesis and lipolysis.  
• Stimulates gluconeogenesis from amino acids and glycerol in the liver, thus raising blood glucose and counteracting the effects of insulin.

1. Growth hormone:

• Stimulates growth and protein synthesis
• Having too little or too much can cause abnormalities in the metabolism of carbohydrates and lipids.
• It increases the responsiveness of adipocytes to lipolytic stimuli
• Stimulates gluconeogenesis  by the liver
• Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue

1. Oestradiol:

• Androgen, synthesised in the ovaries
• Synthesis involves cytochrome p-450 enzymes that cleave the side chain of cholesterol and introduce oxygen atoms
• Affect sexual development, sexual behaviour, and a variety of other reproductive and non-reproductive functions
• Travels to target cells through the blood stream, bound to carrier proteins, they act through nuclear receptors to change the level of expression of specific genes.

1.  17-OH-progesterone

• 17-Hydroxyprogesterone (17-OHP) is an endogenous progestogen as well as chemical intermediate in the biosynthesis of other steroid hormones, including the corticosteroids and the androgens and the estrogens.
• It is derived from progesterone via 17-hydroxylase, a P450c17 enzyme, or from 17-hydroxypregnenolone via 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase.
• 17-OHP increases in the third trimester of pregnancy primarily due to fetal adrenal production.
• This steroid is primarily produced in the adrenal glands and to some degree in the gonads, specifically the corpus luteum of the ovary

1. Aldosterone

• Aldosterone is a steroid hormone (mineralocorticoid family) produced by the outer section (zona glomerulosa) of the adrenal cortex.
• It plays a central role in the regulation of blood pressure mainly by acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium, increase in water retention, and increase in blood pressure and blood volume.
• The corticosteroids are synthesized from cholesterol within the zona glomerulosa of adrenal cortex. Most steroidogenic reactions are catalysed by enzymes of the cytochrome P450 family. They are located within the mitochondria and require adrenodoxin as a cofactor

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