Digestion Of Protein And Carbohydrates Flashcards
What stimulates the secretion of pancreatic amylase?
CCK
Which enzymes are involved in the digestion of starch to oligosachharides?
Salivary amylase
Pancreatic amylase
Which Oligosaccharides are produced form the hydrolysis of starch?
Alpha limit dextrins
Maltose
Maltotriose
What are the three brush border oligosaccharides?
- lactase
- maltase
- sucrase-isomaltase
Where does brush border digestion for oligosaccharides mainly occur?
Proximal Jejunum
Which enzymes are involved in the digestion of alpha limit dextrins?
Isomaltase
Maltase
What are the products of lactose digestion?
Galactose
Glucose
What are the products of sucrose digestion?
Glucose
Fructose
How does the absorption of glucose, galactose and fructose occur in the small intestine?
- Uptake across the apical membrane into the epthelial cell
- Glucose, Galactose- Na/glucose transporter SLGT1
- secondary active transport, glucose inlux occurs against glucose concentration gradient, Na+ gradient maintained by basolateral Na-K pump
- Fructose- GLUT5 transporter- facilated diffusion
- Glucose, Galactose- Na/glucose transporter SLGT1
- Exit across the basolaterla membrane
- facilated sugar transporter GLUT2
What transporter is involved in the transport of glucose and galactose across the apical cell membrane?
SLT-1
What does SLT-1 transporter do?
Transport glucose and galactose across apical cell membrane
What transporter is involved in the transport of fructose across apical cell membrane?
GLUT-5
What is the transport of glucose and galactose called and why?
secondary active transport because its Na driven
How does the three monosaccharides exit the basolateral membrane
through GLUT-2 transporter
What are the symptoms of lactase deficiency after ingestion of lactose
GI symptoms, diarrhea and cramps
Why does individuals with primary lactase deficiency have increased breath H2
Non absorbed lactose is metabolised by colonic bacteria to form H2, which is absorbed into the blood and excreted by the lungs
Which dietry proteins are absorbed intact?
Antigenic proteins
Who can absorb intact proteins in substantial amounts?
Neonates- up to 6 months. From colostrum through endocytosis
What is the first pathway for digestion of proteins
Digestion of proteins into peptides by luminal enzymes. Digestion of peptides into amino acids by luminal enzymes
What is the second pathway for digestion of proteins
Digestion of protein into peptides by luminal enzymes Digestion of peptides into amino acids by brush border enzymes
What is the third pathway for digestion of proteins
Digestion of proteins into oligopeptides by luminal enzymes Oligopeptides are taken up by enterocyte Digestion into intracellular amino acids by cytosolic enzymes Transport across the basallateral membrane into the blood by transporter
What is the fourth pathway for digestion of proteins
Digestion of proteins into oligopeptides by luminal enzymes Oligopeptides are taken up by enterocyte Move directly into the blood
What does gastric chief cells secrete
Pepsinogen
How does pepsinogen get activated
Low intragastric pH
What is pepsin
An endopeptidase with primary specificity for peptide linkages of aromatic and larger amino acids
What are the 5 pancreatic proenzymes
Trypsinogen Chymotrypsinogen Proelastase Procarboxylase A Procarboxylase B
How does the pancreatic proenzymes activate
Trypsinogen by enterokinase. The rest by trypsin
What are the 5 pancreatic enzymes
Trypsin Chymotrypin Elastase Carboxylase A Carboxylase B
What are the products of endopeptidase
oligosachharides with 2 to 6 amino acids
What are the products of exopeptidase
Amino acids
Which pancreatic enzymes are endopeptidase
Tryspin Chymotrypsin Elastase
Which pancreatic enzymes are exopeptidase
Carboxylase A Carboxylase B
For individuals with primary lactase deficiency, what does ingestion of lactose have on plasma glucose concentration?
Smaller rise in plasma glucose
What does brush border peptidase have an affinity towards?
relatively larger oligopeptides- 3-8AAs
What does cytoplasmic peptidase primarily hydrolyse?
di and tri peptides
What transporter is responsible for the uptake of luminal oligopeptides?
PEPT-1
What system is responsible for the uptake of cationic and cystine?
b0
What does b0 system involve?
an Na+ independent transporter for cationic amino acids and cystine. This transporter is an antiporter coupling the uptake to the efflux of neutral amino acids
What system is responsible for the uptake of neutral amino acids?
B0
What does B0 system involve?
an Na+ dependent transporter
What system is responsible for the transport of glycine and proline?
IMINO system
What does IMINO system involve?
Na+ dependent IMINO system and H+ dependent imino acid carrier for the transport of glycine and proline
What system is responsible for the transport of anionic amino acids?
EAAT3 (XAG)
Why is the transport system for anionic amino acids named XAG?
because it involves a Na+ dependent transporter for aspartate and glutamate
Which transporter is involved in the transport of cationic amino acids across the basolateral membrane?
heteromeric antiporter 4F2hc/y*LAT1
Which transporter is involved in the efflux of neutral amino acids
4F2hc independent LAT transporters of the SLC43 family
Hartnup and cystinuria- inheritance
autosomal recessive
What transport is affected in Hartnup and cysteria?
Apical membrane amino acid trasnport
What are the clinical signs associated with Hartnup disease?
Most evident in children- Skin changes of pellagra, cerebellar ataxia and psychiatric abnormalities
Which systems are affected in Hartnup diesease?
System B- neutral amino acids uptake However, oligopeptides containing neutral amino acids are absorbed normally in Hartnup disease
What are the clinical signs assocaited with cystinuria?
kidney stones
Which systems are affected in Cystinuria?
b0+ and B0+ system Cysteine and basic amino acids import are affected
Why is there lack of evidence of protein deficiency in Hartnup and Cystinuria?
More than one transport system for different amino acids Seperate transporter for oligopeptides
What are the two routes responsible for the uptake of intact protein?
Enterocyte-phagocytosis M cells
What happens in Enterocyte phagocytosis?
A small amount of intact protein makes it to the interstitial space. The vast majority is degraded in lysosomes
Where are M cells located?
Payers patches. They have few microvilli and are specialised for protien uptake
What does M cells do?
They package ingested proten in Clathrin-coated vesicles, which they secrete at their basolateral membranes into the lamina propria There, the immunocompetent cells process the target antigen s and transfer them to lymphocytes to initiate an immune response
Give some examples of insoluble dietry fibre
Cellulose and hemicellulose
Give some examples of soluble fibre
Pectins, gums and mucilage
