Production Of Proteases Flashcards
What do chief cells produce?
Pepsinogen
How is pepsin secreted?
As an inactive form zymogen (pepsinogen)
Why is pepsin secreted in inactive form?
To prevent it digesting the chief cells and rest of the body
What is pepsinogen mediated by?
Input from the enteric nervous system via neurotransmitter ACh parasympathetic NS
What is the secretion pepsinogen similar to?
Parallels HCL secretion
Where is pepsinogen released into?
Stomach lumen
What happens when pepsinogen is released into stomach lumen?
The low pH of the stomach due to HCl activates a rapid autocatalytic process in which pepsinogen is converted to pepsin
What is the pathway of pepsinogen to pepsin?
Chief cells release pepsinogen —> pepsin —-> (protein to peptides)
(positive feedback with making of pepsin causes more pepsinogen to form pepsin)
(parietal cells release IF & HCl and HCl activates pepsinogen to pepsin)
When is the conversion of pepsinogen to pepsin most efficient?
pH<2
Once some pepsin is produced, how can more be produced?
Positive feedback loop
Pepsin also catalysts the reaction of pepsinogen to pepsin
When is pepsin only active and what would inactivate it?
Only active at low pH
HCO3- released in duodenum- irreversibly inactive pepsin
Is pepsin from the stomach essential for protein digestion?
Not essential, protein digestion can still occur if stomach is removed
What does pepsin in the stomach do to protein digestion and how much protein digestion does it account for?
Accelerates protein digestion
20% of total protein digestion
What does pepsin in the stomach also help to do?
Breaks down collagen in meat-helps shred meat into smaller pieces with greater SA for digestion
Can we live without a stomach?
what changes would we make?
Yes
smaller meals
B12 Deficiency (stomach secretes IF for absorption of it)
