digestion and absorption Flashcards
Which saccharide bonds does amylase breakdown?
alpha 1-4
What is a glycocalyx?
glycoprotein layer on the microvilli
Where is there NO carbohydrate breakdown?
The stomach
Name the 3 brush border enzymes on the intestinal mucosa
Lactase, Maltase, Sucrase
What is alpha dextrin?
an oligosaccharide that contains alpha 1-4 and 1-6 bonds
Name two enzymes that can break down alpha 1-6 bonds
isomaltase and glucoamylase
Which three disaccharides are broken down by just one specific enzyme?
lactose, trehalose, sucrose
What is the rate limiting step of glucose uptake?
absorption
Which transporter does fructose use?
GLUT5 - apical mem
GLUT2 - basolateral mem
Name two facilitated diffusion transporters
GLUT2 and GLUT5
Where is the main site of protein digestion?
Duodenum
What does enterokinase do?
activate trypsinogen to trypsin
what are endopeptidases?
enzymes that split polypeptides
What are exopeptidases?
enzymes that split end terminal amino acids
How are proteins absorbed?
Via PepT1 on apical mem. This co-transports H+ and the peptide into the cell. Na+ / K+ ATPase required. Then Na+ / H+ exchanger on apical membrane required. H+ gradient used to transport peptide.
What is the function of bile?
Help to solubilise fat and cholesterol
Why do fatty acids head for the smooth ER after diffusing across the cell?
in order to reform into triglycerides to maintain the concentration gradient allowing the free diffusion of the fatty acids into the cell.
How do chylomicrons absorb into the bloodstream?
Via the lacteals of the lymphatic system. Large gaps between lacteals (lymphatic capillary).
What happens in glucose-galactose malabsorption syndrome?
Mutation in SGLT1 transporter, poor uptake. Excess glucose and galactose in lumen of the intestine. Diarrhoea, flatulence, muscle wasting. give lactose instead (uses different transporter)
What is lactose intolerance?
deficiency or dysfunctional lactase
What is hartnup’s disease?
defect in transport of amino acids, appear in urine. Kidney problems
What is gluten enteropathy?
flattened microvilli, poor absorption of gluten. Large amount of fat excreted.
