Topic 11 Endocrine System: Hormone Types

Question 1

• Synthesized in the rough ER and modified in Golgi (requires vesicles to cross membrane). They act on surface receptors typically via secondary messengers (e.g., cyclic AMP)

Answer 1

1. Peptide Hormone

Question 2

• → cleaved in ER lumen to prohormone → cleaved again and modified with carbohydrates in Golgi to final form → packaged by Golgi into secretory vesicles for release via exocytosis

Answer 2

a. Manufactured in rough ER as a larger pre-prohormone

Question 3

• They can move freely though blood but cant diffuse well through the cell membrane of effector (target cell). Instead they attach to membrane-bound receptor -> can trigger one of several effects
  a. Receptor may act as an ion channel, increasing membrane permeability to specific ions
  b. Receptors may activate or deactivate other intrinsic membrane proteins to act as ion channels
  c. Receptor may activate intracellular second messenger systems (hormone is the ‘first’ messenger, and other chemicals act as the ‘second’ messenger) that can create cascade of effects

Answer 3

b. Peptide hormones are water soluble

Question 4

• Protein stimulates production of second messengers (G protein → cAMP produced from ATP; IP3 produced from membrane phospholipids which triggers Ca release from ER)
  a. Note that a G protein doesn’t phosphorylate GDP → GTP; GDP is swapped for GTP, which activates the G protein

Answer 4

c. Example of Receptor-mediated endocytosis

Question 5

• The pancreases is both an exocrine and endocrine gland - it releases digestive enzymes via the pancreatic duct, and insulin + glucagon into blood

Answer 5

Note

Question 6

a. Anterior pituitary: follicle stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH), human growth hormone (hGH), thyroid stimulating hormone (TSH), prolactin
b. Posterior pituitary: anti-diuretic hormone (ADH), parathyroid hormone (PTH)
c. Pancreas: glucagon and insulin

Answer 6

d. Examples of peptide hormones

Question 7

• Synthesized from cholesterol in the smooth ER; are hydrophobic, which means they freely diffuse but require a protein transport molecule to dissolve in blood; have intracellular receptors

Answer 7

2. Steroid Hormone

Question 8

• Steroid hormone diffuses past the plasma membrane and binds to receptors in the cytoplasm → hormone + receptor are transported to the nucleus → binding activates a portion of DNA, acting at the transcription level

Answer 8

a. Direct Stimulation

Question 9

a. Adrenal Cortex: glucocorticoids and mineralocorticoids (cortisol and aldosterone)
b. Gonads: estrogen, progesterone, testosterone (estrogen and progesterone are also produced by the placenta)

Answer 9

b. Examples of steroid hormone

Question 10

• Formed by enzymes in cytosol or on the rough ER

Answer 10

3. Tyrosine Derivatives

Question 11

• Are lipid soluble, require a protein carrier in the blood, and bind to receptors in the nucleus. The response has a latent period and increased duration. These hormones increase transcription of many genes in nearly all cells of the body

Answer 11

a. Thyroid Hormones

Question 12

• Epinephrine and norepinephrine are tyrosine derivatives that are water soluble, dissolve in blood, bind receptors on target tissue, and mainly act via second messenger cAMP

Answer 12

b. Catecholamine

Question 13

• T3 and T4 (thyroxine)

Answer 13

c. Thyroid Hormones