Absorption And Digestion - Dr. Rogers Flashcards
Lactose Intolerance
X digest Dairy Carbohydrates
X lactase enzyme in the brush border (makes it Glucose+Galactose)
Lactose in SI ——> SCFAs and H2 = acetate, butyrate, propionate
= holds H2O in lumen with it
= Osmotic Diarrhea and ferments into methane and H+ gas
Primary Sugars
Sucrose
Lactose
Starch
Secondary sugars
Amylase, Glycogen, EtOH, Lactic Acid, Pyruvic Acid, Pectins, Dextrins
Where does carb metabolism start
Oral cavity, amylase attacks starch
Where is lactose and sucrose attacked in the GI
In the SI most in duodenum (Lactase, Sucrase)
Pancreatic Amylase = starch continues
Most absorption of carbs happens and reason for it
Villi folds called FOLDs of KERCKRING (longitudinal folds) and increase SA
Where are the enzymes found
In the brush border of the villi
Maltose
Trehalose
Lactose
Sucrose
Glucose + Glucose
Glucose + Glucose
Glucose + Galactose
Glucose + Fructose
STARCH breaks down to
- Starch —AMYLASE—> Maltose——> 2Glucose
How is Glucose absorbed
SGLT1 = absorbs glucose and galactose from lumen GLUT5 = fructose absorption from lumen GLUT2 = absorbs glucose + galactose + fructose into blood
SGLT1 inhibitors
Can be used in Diabetes to slow glucose absorption
Which is the fastest sugar transporter
SGLT1 since it used Na+
X GLUT2
Glycogen gets stored in high amounts
How to test for carbohydrate digestion problems
- Breath Tests : methane, CO2 labeled isotope, Lacotse, sucrose
- Ingest D-xylose and see how much is able to get absorbed and present in urine (general statement for carbohydrate digestion problem)
In lactose intolerance what can you find in the tests run
Normal D-xylose
Positive Lactose breath test (H+ and methane sensed)
Protein digestion problems is
X pancreatic enzymes or X transporter of the SI epithelial cells
Chronic Pancreatitis
X pancreatic enzymes - proteases like trypsinogen get activated in pancreas and eats up pancreas and no enzymes are produced
Also no neutralization of stomach
Congenital Trypsin Absence
X trypsin
= no pancreatic enzymes activated
Cystinuria
X SLC3A1 transporter or SLC7A9 (absorb Cysteine, Lys, Arg, Ornithine in proximal tubule of kidney)
= AA secreted in feces and urine
Hartnup Disease
X absorb neutral AA
Pellagra (niacin deficiency)
Mutation in SLC6A19 gene (neutral AA transporter)
Sx: D, mood changes, neuro problems, red scaly skin, photosensitive, NEUTRAL AA in URINE = TRYPTOPHAN + SEROTONIN by products
Cystic Fibrosis
X CFTR transport = cl- channel pumped into cell for HCO-3 facilitated diffusion into stomach and SI to neutralize stomach
= cant move enzymes into GI form ducts
= can lead to pancreatitis
= disrupt gastric and duodenal mucosa
= X protease + X neutralization of stomach
Where does protein get digested initially
STOMACH
Pepsinogen—» Pepsin
10%-20%
Where does most of protein digestion happen
SI from pancreatic enzymes zymogen
Trypsin, chymotrypsin, carboxypeptidase, elastase
——> di and tri peptides