Hormone synthesis Flashcards Preview

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Flashcards in Hormone synthesis Deck (15):
1

What type of hormone is insulin?

Protein hormone

2

What are the steps of making insulin?

1. Gene expresses the protein coding for insulin and is transcribed to make RNA

2. Splicing of RNA = mRNA

3. mRNA leaves the cell nucleus and goes to the ribosome

4. In ribososme preproinsulin is formed

6. Preproinsulin travels to the ER

7. Here, preproinsulin is modified into proinsulin

8. Proinsulin travels to the Golgi and is modified to form mature insulin

3

What is the structure of preproinsulin?

This is a preliminary protein

Composed of three chains: A, B and C

Contains signal sequence: makes the insulin inactive

4

What is the role of the signal sequence?

Direct the insulin from the ribosome to the ER

5

What happens when signal sequence is cleaved off?

Preproinsulin -> proinsulin

6

What modifications happen in the ER?

Signal sequence is cleaved off

Disulphide bridges form between A and B chains

7

Which enzymes cleave off the signal sequences?

Proteolytic enzymes

8

What are disulphide bridges?

Oxidation of thiol groups

9

What happens to the proinsulin when it enters the Golgi?

Modified to form mature insulin

Splice away the C chain

10

What is the process of synthesising peptide hormones?

1. Gene codes for POMC

2. This is transcribed and translated

3. Split via proteolytic enzymes to form hormones

11

What does POMC stand for?

Proopiomelanocortin

12

What hormones are synthesised by the cleavage of POMC?

MSH

ACTH

Endorphins

13

How are steroid hormones synthesised?

Made from cholesterol

1. Cholesterol makes pregnenolone precursor

2. Modification of cholesterol can happen anywhere alonng the carbon chain to form the hormones

3. Different enzymes catalyse these reactions

14

What are examples of enzymes that modify cholesterol?

11 hydroxylase - enzyme that hydroxylates (adds OH) to cholesterol on C-11

21 hydroxylase - enzyme that hydroxylates C-21 on cholesterol

15

What are examples of steroid hormones?

Glucocorticoids - further modified to make mineralocorticoids

GC : Cortisol

MC: Aldosterone

Androgens - further modified to make oestrogens