GI Digestion and absorbtion. Flashcards
What confirmation of amino acids are found in proteins in the human body?
L
What are the two phases of protein digestion?
Gastric and Intestinal.
Which enzymes causes the breakdown of proteins in the stomach and how?
Pepsin which causes the breakdown of proteins into smaller peptides by breaking the collagen links.
What are the precursors to pepsin and where are they produced?
Pepsinogen I= In HCl secreating regions of the stomach only.
Pepsinogen II= Only in the pyloric region.
What occurs in the intestinal phase of protein digestion.
Pancreatic juices and intestinal juices mix and completely break down peptides to amino acids.
What protease enzyme is found in the pancreatic juices?
Chymotrypsinogen and trypsinogen (inactive form)
What causes the activation of the pancreatic proteases in the small intestine?
Enteropeptidase activates tripsinogen to trypsin and trypsin activaes chymotrypsinogen to chymotrypsin.
What does the digestion in the intestinal lumen produce?
Oligopeptides.
What is the first stage of protein absorption?
Olgiopeptides are further broken down by membrane amino-oligopeptidase enzymes.To single, di or tri peptides.
What is the second stage of protein absorption?
Transport of single di/tri peptides to cytoplasmic space via transport pumps. Amino acids enter via a sodium pump. Di and Tri enter together by a transport protien.
What is the third stage of protein absorption?
Cytoplasmic digestion to amino acids via di and tri peptidases.
What is the final stage of protein absorption?
Passive diffusion out of the cell into local capillaries.
What are the two forms of carbohydrates?
Free sugars which cause a rapid shift in blood glucose as are quickly absorbed.
Slow digesting.
What is the first stage of carbohydrate digestion?
Alpha amylase in the saliva starts digestion.
How does alpha amylase work?
It hydrolyses alpha amylase bonds in large polysaccharides to make glucose and maltose.
Where does alpha amylase function?
From the mouth to the stomach where it is deactivated by low pH.
What is the second stage of carbohydrate digestion?
Pancreatic amylase continues digestion to maltose, maltriose and larger polysaccharides.
What is the final stage of carbohydrate breakdown?
Microvilli in small intestine have oligosacharidases e.g. maltase, lactase, sucrase and dextrinase.
What are the oligosaccharidases in the SI?
Maltase, lactase, sucrase and dextrinase.
What causes lactose intolerance?
Amount of lactase produced decreases with age. If lactose is not broken down it continues to the colon causing more water to be excreted .
How are hexoses and pentoses absorbed?
Passes easily across intestinal mucosa to the portal vein.
How is glucose absorbed?
Via na+/glucose co-transporter into cells. THen via GLUT2 pump into the blood.
How is galatose absorbed?
It follows glucose.
How is fructose absorbed?
An independent fructose carrier.
