22313541
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
about 4 years ago
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| Question | Answer |
| After salivary amylase: -pancreatic amylase cleaves straight chains only to produce short ..., ..., and ... - further digestion to monosaccharides by .... | 1. ogliosaccharides 2. Maltose 3. Maltriose 4. Brush border enzymes |
| Detail how the following are absorbed: 1. Free amino acids 2. Di/Tri peptides 3. Larger peptides | 1. AA absorbed via Na+ linked lumenal transporters, then exit cell on basolateral side into capillary 2. Di/Tri peptides absorbed via H+ linked lumenal transporters, hydrolysed into AA, then exit into capillary 3. Larger peptides broken down into peptidases into the above two first |
| Digestive functions are localised where... | 1. optimal pH of enzymes differ 2. Enzymes secreted as inactive precursors and need activation by enzymes 3. Some enzymes bound to membrane |
| How are glucose and galactose absorbed? What kind of transport is involved? | 1. SGLT (Na+ linked transporter) provides secondary active transport into the lumenal membrane 2. GLUT2 transports them out into basolateral membrane via facilitated diffusion |
| How does H20 get reabsorbed in the colon? What stimulates H20 and Na reabsorption? What is the role of microflora in the colon? | 1. Via osmosis down the Na+ gradient 2. RAAS system via Aldosterone 3. produce Vit. K and folic acid (absorbed here) |
| How does malabsorption lead to osmotic diarrhoea? | 1. There is increased solute load in the SI load so water stays with it 2. Increased volume stimulates peristalsis 3. Undigested fats also have laxative effect |
| How is fructose absorbed? What type of transport is involved? | 1. GLUT5 transporter via facilitated diffusion on lumenal membrane 2. GLUT2 transports it out via facilitated diffusion on the basolateral side |
| What are carboxypeptidase and aminopeptidase and what do they do? | 1. They are exopeptidases 2. Carboxypeptidase removes AA from carboxyl terminal, while Aminopeptidase removes AA from amino terminal |
| What are two other causes of diarrhoea (excluding osmotic)? | 1. Secretory activity by intestinal crypt cells in response to bacterial infection 2. Intestinal mucosal damage (eg. coeliac/Crohn's disease) |
| What are some causes of malabsorption? | Failure to: 1. digest macromolecules in chyme 2. absorb certain molecules (eg. lactose) 3. absorb B12 (needs intrinsic factor0 4. absorb iron (need acid pH) |
| What are the 3 places carbohydrate digestion occurs? What are their optimal pHs? | 1. Salivary amylase in mouth (pH 6.8) 2. Pancreatic amylase (pH 7.1) 3. Small intestine membrane bound disaccharides (pH 6-7) |
| What are the main components of the small intestine villus? | 1. Villi to increase SA 2. Single epithelial layer so macromolecules have short diffusion distance 3. Goblet cells that secrete mucus 4. Enterocytes absorb nutrients 5. Stem cells at base of crypt 6. Lymph system for fat-->lacteal 7. Microvilli on brush border w transporters/digestive enzymes |
| What are the steps of fat absorption? | 1. Free fatty acids/monoglycerides diffuse into membrane 2. Resynthesis of triglyceride in SER 3. Packaging of triglyceride into chylomicrons 4. Chylomicrons exocytosed, enter a lacteal |
| What are the steps of fat digestion? | 1. Emulsification of fat in lumen with bile salts 2. Lipase converts triglycerides to monoglycerides/fatty acids 3. Formation of micelles 4. Diffusion of micelles to epithelial brush border |
| Fat ... happens then at the epithelial brush border fat... happens | 1. Digestion 2. Absorption |
| What cell junctions are there in the small intestine? | Tight junctions for a barrier function |
| What does the chief cell and parietal cell secrete? | The chief cell secretes pepsinogen The parietal cell secretes intrinsic factor and HCl |
| What is the role of pepsinogen and HCl in protein digestion in the stomach? | Pepsinogen is broken down into pepsin by the Hcl secreted by the parietal cell First step in protein digestion |
| What gradient is maintained inside a small intestine enterocyte? How is this maintained? | 1. Low Na+ within the cell to drive Na+ reabsorption from the lumen 2. Maintained via Na+/K+ ATPase |
| What is chyme? Where is it released? What other factors are required for the digestion of food? | 1. Acidic fluid w partially digested c/p/f/intrinsic factor 2. Released from stomach in duodenum 3. enzymes (pancreas/enterocytes), pH neutralised, bile salts |
| What is required for fat digestion/absorption? | 1. Pancreatic/gastric lipase 2. Colipase in duodenum 3. Bile salts in duodenum 4. Right pH in duodenum 5. B-lipoprotein in RBC to package chylomicrons |
| What is the role of intrinsic factor from parietal cell? | Enables VitB12 absorption in small intestine |
| What is the second stage of protein digestion? 1. In the duodenum, enzyme ... on brush border of enterocytes activate ...-->... 2. Trypsin activates... of the pancreas 3. ..., ... and ... cleave peptide bonds to produce short peptides 4. ... remove amino acids from terminals of peptides | 1. Enterokinase 2. Trypsinogen-->trypsin 3. Proteolytic enzymes of the pancreas 4. Trypsin, elastase, chymotrypsin 5. Exopeptidases |
| What is the unstirred layer of the small intestine? | A layer which does not get churned about even with passing food stuff |
| Where are bile salts reabsorbed? How do they reach to liver and be reused? How much bile salt is lost? | 1. Terminal end of ileum 2. Portal vein transports in back into liver, where RBC reextracts it 3. 5-10% lost in faeces |
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