Small Intestine Digestion of Carbohydrates and Proteins Flashcards
Structure of small intestine
Hypoxia at the tip of villus
Anything leading to dec BP leads to ischemic or necrotic bowel dz
Epithelia lcells constantly turning over
Carbs in general
Some are indigestible…cellulose has beta-glycosidic bonds cleaved by bacteria
No required
Straight chains - alpha 1,4
branch - alpha 1,6 (digested by alpha-dextrinase)
Hydrolysis
Alpha-amylase only cleave non-terminal 1-4 alpha linakges
Saivary from parotids cleaves starch to maltose and oligos…not required
Pancreatic amylase - completes digestion within 10 min after chyme enters….developmental delay
BB disachs - primary sub is disach but can work on others…INCREASES rate of absorption of some disachhs
Disaccharidases
Lactase
Sucrase
Alpha-dectrinase
Tend to be highly glycosylated to protect from proteases
Lactose to glucose and glaactose
Sucrose to fruct and glu
Oligos to flucose
Abs of monos
Active mostly in the duodenum and jenunum
SUgars are osmotically active and must be rapidly abosrped to prevent excessive water lfux into the lumen
Active transport mech of carbs
Majority of glucose absorption
Very rapid uptake of glucose by SGLT1 creates a low conc at luminal surgfce
GLUT2 on basolateral
Needs Na/K ATPase on basolateral
SGLT1 is same as kidney but function unaffected by insulin
Fructose
More likely to be malabsorped due to GLUT5 low transport maximum
Conseuqences of CHO malabsorption
Bact metabolize CHO to smaller things that lead to gas, mootility diarrhea
Most common dysfunction is lactose intolerance…lactase may dec after infancy if not a lot of milk products
Protein intake and in general
Animal includes all essential
Amost 4g per day lost in stool
Required 45 g/day due to NH4 loss
Hydrolysis of proteins
Endopeptidases break internal bonds
All secretes as zymogens
Pepsin is about 15% and is not mandatory
Intestinal proteolsysi via trypsin, chymotrypsin and carboxypeptidases…activated by enteropeptidase/trypsin cascade…NNEED pancreatic fxn in order to work
Most brush border in the proximal jejunum
Similarities of CHO and protein
Na important in uptake
Some slight pinocytosis of larger
Lysosomes and ER play role in trnasport
Dipeptides absorbed more quickly than free AAs
Uptake of proteins
ENergy dep and need Na/H exchange on apical
Celiac
Harnups
CF
Creatorrhea
Lack of BB, microvilli so def in enzymes and trnasporters
Loss of transport of neutral AA
Pancreatic enzynmes almost completely absnet
Protease def or AA uptake issues
