Hormone Synthesis and Action ADDITIONAL

Question 1

What is the function of the signal sequence?

Answer 1

Signal sequence allows the protein to be sequenced within a protein granule.

Question 2

Synthesis of insulin

Answer 2

1) Transcription to mRNA
2) Excision of introns to messenger RNA
3) Removal of signal sequence and formation of disulphide bonds in RER
4) Pre-proinsulin -> proinsulin
5) Transfer to Golgi apparatus, excision of C peptide and packaging into secretory granules

Question 3

Outline steroid synthesis

Answer 3

1) Cholesterol -> Pregnenolone
2) Pregnenolone:
a) -> Progesterone
b) -> 17αOH Progesterone
3a) Progesterone -> Aldosterone
3b) 17αOH Progesterone:
• Cortisol
• Androgens (Aromatase needed to make oestrogen in women) - Oestrogen is important in bone formation and epiphyseal closure of bones.

• Aromatase deficiency in men - unable to synthesise oestrogens from androgens -> no epiphyseal closure -> long stature

Question 4

What is Graves disease?

Answer 4

Grave’s Disease is when you have a faulty, overactive receptor. Antibodies to the TSH receptor act on the thyroid gland, stimulating excess hormones. This can also cause eye disease.
– overactive thyroid stimulating receptor – due to autoimmune disease (not a mutation). – phenotypes include enlargement of glands and protruding eyes.

Question 5

What is AIS?

Answer 5

Androgen insensitivity syndrome.

• when you cannot respond to steroid hormones
• due to mutations in the receptors, or lack of synthesis of the receptors.