L8: DIgestion and Absorption Flashcards
Absorption in the Duodenum?
Iron
Calcium
Fat
Sugars
Amino Acids
Absorption in the Jejunum?
Sugars
Amino Acids
Absorption in the Ileum?
Bile Salts
Vitamin B12
Absorption in the Colon?
Water
Electrolytes
Anemia and osteoporosis are symptoms of ______________________due to poor iron and mineral absorption as a consequence of ________________
Anemia and osteoporosis are symptoms of coeliac disease due to poor iron and mineral absorption as a consequence of villous atrophy
Carbohydrate digestion occurs via ______________, _________ and ____________enzymes
Different bond types acted on by different enzymes:
- Straight chain (1:4 alpha) acted on by __________________
- __________________ breaks down 1:6a bond
Carbohydrate digestion occurs via Salivary, Pancreatic and Brush border enzymes
Different bond types acted on by different enzymes:
- Straight chain (1:4 alpha) acted on by glucoamylase
- Alpha Limit Dextranase breaks down 1:6a bond
Only _________________ can cross the epithelial barrier so carbohydrates must be digested to their simplest form
Only mono-saccharides can cross the epithelial barrier carbohydrates must be digested to their simplest form
Dimer of Glucose and Fructose?
Sucrose
Dimer of Galactose and Glucose?
Lactose
Dimer of Glucose with 1:4 Alpha Linkages?
Maltose (Not absorbed by small intestine)
_______________________:
Deficiency in Lactase at the brush border
>50% of adults globally
Lactose Malabsorption Syndrome:
Deficiency in Lactase at brush border
>50% of adults globally
____________________________:
Rare congenital disorder associated with inability to digest Lactose
Also affects infants
Congenital Lactose Intolerance
Rare congenital disorder associated with inability to digest Lactose
Also affects infants
___________________________:
Inherited digestion disorder (Greenland Inuit)
Treated w/ low sucrose diet
Sucrase-Isomaltose deficiency
Inherited disorder (Greenland Inuit)
Treated w/ low sucrose diet
Absorption of Carbohydrates in Low Glucose Conditions (FASTING STATE)?
Secondary active transport coupled to Na+ (Maintained by basolateral Na/K Exchanger)
- Glucose/Galactose:: hitches a ride across apical w/ Na via SGLT1 Co-Transporter (Sodium/Glucose enter at 2:1 ratio)
- Fructose has its own transporter: GLUT (facilitated diffusion across apical)
Facilitated transporter (GLUT2) allows all to exit on the Basolateral Surface (along concentration gradient w/o ATP)
Absorption of Carbohydrates in High Glucose Conditions (AFTER MEAL)?
Adults vs. Neonates Protein Absorption?
Adults: Peptides, Dipeptides and Tripeptides transported across brush border (Proteins do NOT Need to be in simplest form to be absorbed)
Neonates: In addition to the above are also capable of taking up larger protein molecules via receptor mediated endocytosis of immunoglobulins in colostrum
Transport of single amino acids usually ________ than di/tripeptides
Stereospecific: higher affinity for____-amino acids
Transport of single amino acids usually slower than di/tripeptides
Stereospecific: higher affinity for L-amino acids
Digestion of proteins begins in the _______________
_________, _____________ and ____________ proteases digest peptides
Digestion of proteins begins in the Stomach
Pancreatic, Brush Border and Intracellular Proteases digest peptides
Amino Acids vs. Peptide Absorption?
Dipeptides/Tripeptides: co-transported into cell w/ Hydrogen ions. Catabolized to AAs by peptidases within cell
Amino Acids: Absorbed by SPECIFIC amino aid transporters for acid, basic and neutral amino acids!! (FAST)
- Absorption of neutral amino acids is very similar to the mechanism used for absorption of glucose (Na- Contransporter)
3 lipases secreted by Pancreas:
- ____________________________=> 2 free fatty acids + monoglyceride
- _____________________________=> 1 free fatty acid + cholesterol
- ____________________________ => 1 free fatty acid + lysophosphatide
3 lipases secreted by Pancreas:
- Triacylglycerol Hydrolase => 2 free fatty acids + monoglyceride
- Cholesterol Ester Hydrolase => 1 free fatty acid + cholesterol
- Phospholipase => 1 free fatty acid + lysophosphatide
Steps of Absorption of Lipids?
Step 1: Emulsification of fat via Bile Salts and Phospholipids
Step 2: Smaller Emulsion Droplets via Bile Salts and Pancreatic Lipase (Lipases water soluble, only access lipids at the interface)
Step 3: Micelle Formation (Biles Salts/Phospholipids)
Step 4: Passive Diffusion across epithelial cell
Step 5: Resynthesis of lipids in SMOOTH ER of epithelial cells
- 2-monoglycerides => Triglycerides
- Lysophospholipids => Phospholipids
- Cholesterol is re-esterified (some free cholesterol remains)
Step 6: Chylomicron Formation and Transport
Bile acids require __________ to emulsify lipids into 1μm droplets
Bile acids require lecithin to emulsify lipids into 1μm droplets
Bile salts and phospholipids form _________ for the transport of Monoglycerides , cholesterol and Fat soluble vitamins
Bile salts and phospholipids form micelles for the transport of Monoglycerides , cholesterol and Fat soluble vitamins
In the __________________ the bile salts are re-cycled by Enterohepatic Re-Circulation:
- _____________ – Apical sodium-dependent bile salt transporter
- _____________ – Baslolateral sodium-independent bile acid transporter
In the Terminal Ileum the bile salts are re-cycled by Enterohepatic Re-Circulation:
- ASBT – Apical sodium-dependent bile salt transporter
- OSTa/b- Baslolateral sodium-independent bile acid transporter
> ____ g of fat in faeces/day is defined as fat malabsorption. Causes?
>7g of fat in faeces/day is defined as fat malabsorbtion
Causes:
- RAPID TRANSIT
- LUMINAL DIGESTION REDUCED
- BILE ACID DEFICIENCY - Gall Bladder Removal
- MUCOSAL/LYMPHATIC TRANSPORT REDUCED
- GLUTEN ENTEROPATHY Lipid malabsorption
Triglyceride Transport
- Triglycerides delivered to adipose tissue via __________ from the GIT (Mainly Triglycerides, some cholesterol, phospholipids, and protein)
- Triglycerides are delivered to the adipose tissue via ________ from liver
- Remnant Chylomicrons are processed in the liver where new _________________ are formed
Triglyceride Transport
- Triglycerides delivered to adipose tissue via Chylomicrons from the GIT (composed mainly of Triglycerides, some cholesterol, phospholipids and protein)
- Triglycerides are delivered to the adipose tissue via VLDL from liver
- Remnant Chylomicrons are processed in liver where new liposomes (HDL + LDL) are formed
TG Storage in Adipose Tissue: TAG Synthesis (_____________)?
Chylomicron (via __________________ in adipose endothlium)=> Fatty Acid Release (Via _________________________) => Triglycerides Storage
TG Storage in Adipose Tissue: TAG Synthesis (Esterification)?
Chylomicron (via Lipoprotein Lipase in adipose endothlium)=> Fatty Acid Release =(Via a- glycerol phosphate (from glucose)) => Triglycerides Storage
