Topic 7: Endocrine System - Types of Hormones

Question 1

What does the endocrine system regulate? (3)

Answer 1

• growth
• reproduction
• metabolism (long-term events)

Question 2

What generally occurs in the endocrine system? (2)

Answer 2

• glands and tissues secrete hormones which travel in blood to target cells (cells w/ specific receptors for that hormone)
• binds to receptors and changes cell activity

Question 3

Where are receptors (proteins) found? (2)

Answer 3

• on cell membrane
• intracellular (nuclear)

Question 4

what type of hormones are water soluble? (3)

Answer 4

• peptides
• proteins
• catecholamines (1st messengers)
  ex. NE, Epinephrine

Question 5

What occurs when a WATER SOLUBLE hormone binds to a receptor? (3 steps. 5 points)

Answer 5

1. hormone binds to cell membrane receptors
   - do not enter cell for their actions
2. hormone-receptor complex activates membrane proteins like G-proteins
3. G-proteins then activate 2nd messenger systems
   - ex. cAMP, Ca2+

Question 6

Name the steps in which cAMP acts as a second messenger when it bind s to a receptor. Remember that it is water soluble! (5 steps, 7 points)

Answer 6

1. Hormone binds to cell surface receptor and activates a G-protein
2. G-protein activates adenylate Cyclase (membrane protein)
3. Adenylate Cyclades converts ATP to see a cAMP
   - second messenger; therefore increased conc
4. cAMP activates protein kinases in cytosol
5. Protein kinase acts on other proteins (phosphorylates) to alter their activity, therefore changing cell activity

Question 7

Give an example of cAMP and epinephrine acting (3)

Answer 7

1. epinephrine on liver cells activates cAMP
2. causes breakdown of glycogen to glucose
3. released to blood
   - in lecture, it occurs when low blood glucose levels

Question 8

Why do we use second messenger systems? (4 steps, 5 points)

Answer 8

• hormones cannot enter cell (water-soluble)
• rapid acting (enzyme is already present, just activate)
• 1 hormone molecule = many enzyme molecules activated and then multiplies signals (cascade)
• limited, where messenger is broken down or removed
  ie. cAMP broken down by phosphodiesterase in the cell

Question 9

What are two examples of lipid soluble hormones? (2)

Answer 9

• steroids (ie. cortisol)
• thyroid hormones

Question 10

What is the function of lipid soluble hormones?

Answer 10

• triggers protein synthesis

Question 11

How long is the time for lipid soluble hormones to take effect? (2)

Answer 11

• takes time (slow)
• BUT long lasting response

Question 12

What occurs when a lipid soluble hormone binds to a receptor? (3)

Answer 12

1. enters target cell and bind to intracellular (Nuclear) receptors in cytosol or nucleus
2. Hormone-receptor complex binds to a specific region on DNA, which activates genes to start gene transcription to produce mRNA
3. mRNA attaches to ribosomes to produce proteins (translation)