Flashcards in Nutrient Absorption Deck (47):
How can water obstruct nutrient absorption?
It forms a layer at the mucosal wall with H-bonds when undisturbed
Impediment to nutrient absorption presented by lack of flow in gut
Water forms layer around intestinal wall with H-bonds.
Microviliated apical tip of enterocytes in small intestine
Which cells secrete mucus in stomach?
Which cells secrete acid in stomach?
Which cells secrete pepsinogen in stomach?
Average lifespan of an enterocyte
Migration of entreocytes:
1) Stem cells located in crypts
2) Migrate upwards towards vili
3) Differentiate as migrate
What do crypt cells secrete?
Gluten causes autoimmune disease
Results in epithelium on villi dying
Enzyme that breaks down polysaccharides
Macromolecule broken down by amylase
Environment in which amylase works the best
Efficiency of amylase in mouth
Food not broken down enough for amylase to access much surface area
Method of digestion in stomach
Peristalsis grinds food against pylorus to break it down
Where does amylase become effective?
In the duodenum
Bicarbonate neutralises acid
Hormones released when food enters duodenum
Role of secretin
Activates water secretion
Activates bicarbonate secretion
Inhibits stomach emptying
Action of secretion
Enters blood, stimulates pancreas
Stimulates pancreatic amylase release into duodenum
Types of absorbable sugars
Glucrose, galactose, fructose
How do glucose and galactose cross apical membrane?
Sodium-glucose linked transporter (SGLT)
What powers the sodium-glucose linked transporter?
Sodium gradient across endothelial wall
What converts pepsinogen to pepsin?
Breaks bonds within a polypeptide chain
Limit of endopeptidases
Can't produce individual amino acids
Where does fat sit in the stomach?
On top of carbs and proteins
Which pancreatic proteases are released upon cholecystokinin signalling?
Factors released upon cholecystokinin signalling
Remove amino acids from the ends of proteins
Types of exopeptidases
How are pancreatic proteases secreted?
How is protrypsin converted to trypsin?
Enteropeptidase in the brush-border membrane
Enzyme activated by enteropeptidase in the brush-border membrane
Protrypsin --> trypsin
Which enzymes are activated by trypsin?
Chymotrypsinogen --> Chymotrypsin
Procarboxypeptidase --> Carboxypeptidase
What converts chymotrypsinogen to chymotrypsin?
What converts procarboxypeptidase to carboxypeptidase?
Which factor stimulates trypsin release?
What is the pathway for secreted chymotrypsin?
Cholecystokinin --> Protrypsin --> Trypsin --> Chymotrypsinogen --> Chymotrypsin
Types of exopeptidases in the brush-border membrane
Where are fats mostly broken down?
Which fat can stimulate CCK release?
Free fatty acids
An effect of CCK release
Feel sated, release bile (for fat digestion)