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Lecture 38
Digestion and Absorption
| Term | Definition |
|---|---|
| Carbohydrate Digestion | must be reduced to monosaccharides to be absorbed |
| Complex Carbohydrates | chains of sugars,usually glucose. diff complex carbs have diff links btw sugars.starch is diff than cellulose-we cannot digest cellulose.sugar in fruit is often monosaccharide,fructose or glucose |
| Enzymes | produced in the mouth and in the pancreas. amylase converts starch into disaccharides. dissach are in the wall of the SI. disacch convert dissach into monosacch.sucrose is converted to glucose and fructose |
| Lactose Intolerance | lactose is milk sugar-disac of glucose and gelatose. if no lactase is produced-no degestion of lactose. bacteria in LI use lactose as food source. gas and diarrhea produced |
| Absorption | complete-all sugars totally absorbed.no diffusion-use glucose transporters. |
| Sodium Dependence | glucose co-transport w/ na+ into epithelial cells.transport of glucose from epithelial cells to interstitial fluid uses a non na+ glucose transporter |
| Protein Digestion | some in stomach,most in small intestine |
| Proenzymes | released in protected form.acid,then pepsin,converts pepsinogen into pepsin. enterokinase in SI wall converts trypsinogen into trypsin.trypsin then converts other pancreatic proteases into active form |
| Peptidases | both from pancreas and on SI wall.convert peptides into amino acids.some di-and tri-peptides absorbed |
| Absorption | use amino acid transporters in mucosal wall.some use na+,cl- or no cotransporter |
| Sources of Protein | 50% food,25% digestive enzymes,25% mucosal cells.no dietary proteins in feces |
| Infant Protein Absorption | newborns can absorb protein directly until tight junctions form IgG in colostrum provides protection |
| Lipid Digestion | mouth and stomach lipases umimportant.pancreatic lipases enter duodenum in an active form |
| Lipases | convert lipids to absorb form.lipases convert trigylcerides into monoglycerides and free fatty acids |
| Micelles | bile cells from liver emulsify MG and FFA and cholesterol. fats diffuse into mucous at brush border |
| Absorption | MG and FFA cross and reform into TG in mucosal cells.TG and cholesterol form chylomicron. chylomicrons enter lymph,thru thoracic duct to blood |
| Portal Vein | carries water soluble foods directly to liver.liver processes and detoxifies foods. fats causes lymph causes blood causes everywhere causes liver (eventually) |
| Electrolyte Absoption | salts all h2o soluble leads to portal vein.SI has tight junc. salts use carries,channels,and pumps to go thru cells |
| Water | 2000 mL/daY ingestion,7000mL/day secretions.200mL/day in stool.follows other absorption osmotically |
| Sodium | most na+ enters through cells,energy gradient from na+ pumps on basolateral side of mucose (as in kidney).some na+ entry through leaky tight junctions |
| Potassium | k+ enters through down concentration gradient through k+ channels K+ exchanged for na+ last electrolyte absorb.during diarrhea k+ loss too fast for k+ reab.active transport of k+ in colon. |
| Bicarbonate | huge secretion by pancreas,buffers acids in duodenum.reab by concentration gradient in SI |
| Vitamins | water soluble B and C vitamins rapidly absorb,rapid loss in urine.must take in b and c vitamins daily.b12 absorp needs intrinsic factor from stomach.vitamins a,d,e,k fat soluble leads to micells leads to lymph |
| Minerals | ca2+ 30-80% absorbed-vit D dependent.ca2+ binding proteins and ca2+ ATPase inc ca2+ entry |
| Digestion and Absorption | the breaking down of food into absorbable units and their absorption |
Created by:
danamarie9323
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