Biochemistry LE 5: Hormones that Regulate Fuel Metabolism

What is the structure of somatostatin?

Cyclic peptide with an internal disulfide bond

How many amino acids does somatostatin consist of?

14 amino acids

What is the function of the cysteine residues in somatostatin?

They form an internal disulfide bond

What type of hormones are generally mediated by the cAMP pathway?

Lipophobic hormones Signup and view all the answers

What is the characteristic of lipophobic hormones in terms of the phospholipid bilayer?

They cannot penetrate the phospholipid bilayer Signup and view all the answers

What is the role of cell-surface receptors in the mode of action of lipophobic hormones?

They bind to the hormone and initiate a signaling pathway Signup and view all the answers

What is the term for the type of hormones that include somatostatin?

Class II hormones Signup and view all the answers

What is the effect of Madarcos on penile blood vessels?

Vasodilation Signup and view all the answers

What is the result of somatostatin binding to its receptor?

Inhibition of neurotransmitter secretion Signup and view all the answers

What is the action of phosphotyrosine phosphatase (PTPase)?

Regulate protein phosphorylation Signup and view all the answers

What is the effect of somatostatin on the release of GH from the anterior pituitary gland?

Inhibition Signup and view all the answers

What is the target of the third signaling pathway of somatostatin?

Regulation of PTPase and MAPK Signup and view all the answers

What is the effect of somatostatin on the digestive process?

Inhibition Signup and view all the answers

How many subtypes of somatostatin receptors (SSTRs) are there?

5 Signup and view all the answers

What is formed when epinephrine binds to its cell membrane receptor?

Epinephrine-Receptor Complex Signup and view all the answers

What replaces GDP bound to G protein (𝐺𝑞) in the α-adrenergic pathway?

GTP Signup and view all the answers

What is activated by 𝐺𝑠 with bound GTP in the α-adrenergic pathway?

Phospholipase C Signup and view all the answers

What is cleaved by active Phospholipase C (PLC) in the α-adrenergic pathway?

Phosphatidylinositol 4,5-bisphosphate (PIP2) Signup and view all the answers

What is the water-soluble compound produced by the cleavage of Phosphatidylinositol 4,5-bisphosphate (PIP2)?

Inositol 1,4,5 triphosphate (IP3) Signup and view all the answers

What happens to the sequestered 𝐶𝑎2+ ions when IP3 binds to its receptor?

They are released into the cytoplasm Signup and view all the answers

What is the effect of increasing calcium levels in the cytoplasm?

Promote exocytosis of calcium from the ER Signup and view all the answers

Where does 11-β-Hydroxylase act on 11-Deoxycortisol?

Mitochondria Signup and view all the answers

What is the end product of the cortisol synthesis pathway described in the text?

Cortisol Signup and view all the answers

What is the function of 3-βHSD in the cortisol synthesis pathway?

It reduces oxygen at carbon 3 Signup and view all the answers

What is the effect of increased cortisol levels on the hypothalamus and pituitary gland?

It causes a negative feedback inhibition on the hypothalamus and pituitary gland Signup and view all the answers

What is the role of Corticotropin Releasing Hormone (CRH) in the regulation of cortisol synthesis?

It stimulates the pituitary gland to produce cortisol Signup and view all the answers

What is the difference between cortisol and other hormones in terms of their mechanism of action?

Cortisol can directly stimulate certain segments of DNA Signup and view all the answers

What is the first step in the cortisol synthesis pathway described in the text?

Madarcos, MD → Δ5,4 isomerase moves the double bond from between carbon 5 and 6 to carbon 4 and 5 Signup and view all the answers

What is the primary disorder associated with Congenital Adrenal Hyperplasia (CAH)?

Hyperfunction Signup and view all the answers

What is the result of a defect in the activity or amount of an enzyme in the steroidogenic pathways?

Deficiency in the synthesis of hormones beyond the affected step Signup and view all the answers

What is the clinical manifestation of glucocorticoid deficiency and overproduction of androgens in patients with Congenital Adrenal Hyperplasia (CAH)?

Hypertension and masculinization in females Signup and view all the answers

What is the parent compound in the synthesis of sex hormones, cortisol, and mineralocorticoids?

Cholesterol (C27) Signup and view all the answers

What is the effect of congenital deficiency of steroid hydroxylases on ACTH?

No feedback inhibition of ACTH Signup and view all the answers

What is the result of increased production of deoxycorticosterone?

Hypertension Signup and view all the answers

What is the clinical manifestation of Cushing's Syndrome?