[4] Digestion and Absorption Flashcards
Small Intestine Surface Area gets amplified how many times?
600x
Composition:
Sucrose
Lactose
Maltose
Glu-Fru
Glu-Gal
Glu-Glu
Carbohydrates compose what % of our diet
50-60%
What is more effective? Ptaylin or Pancreatic Amylase?
Ptyalin: 20-40%
Pancreatic Amylase: 50-80%
% Digestion
Triglycerides require _____ and _____ to become ____ and ____
Colipase and Lipase
Fatty Acids and Monoglycerides
Phospholipids require _____ to become ____ and ____
Phospholipase A2
Fatty Acids and Lysolecithin
In a normal intestine which is greater? Absorption or Secretion?
Absorption > Secretion
SCFA’s are taken up by?
Colonocytes
Fat-Soluble Vitamins
ADEK
Where are Bile Acids and Vitamin B12 absorbed?
Ileum
What do you need to properly absorb Calcium?
Vitamin D
Should you take calcium before, during, or after meals?
2 hours after
Some food can interfere with Ca uptake
What state is it easier to uptake iron in? Ferrous or Ferric?
Ferrous (Fe2+)
What can decrease iron absorption?
Tannins (Non-herbal Teas)
Phytates, wheat, and other cereals
What is the storage form of iron in the body?
Ferritin
Best site of absorption of Carbohydrates?
Duodenum
[Effect on Absorption]
- Lipid Solubility
- Size
- Presence of Special Carrier
- Electrochemical Gradient
- = +
- Smaller = +
- W/ special carriers = +
- = +
Effect of Plicae Circulares on Surface Area
x3
Effect of Villi on Surface Area
x10
Effect of Microvilli on Surface Area
x20
How is sucrose digested?
Membrane Digestion
Occurs at the immediate vicinity of the brush border
How are proteins digested?
Luminal Digestion
With proteases occuring within GI lumen
How are some tri and dipeptides absorbed?
Intracellular Hydrolysis
How are triglycerides taken up?
Luminal hydrolysis by lipase -> Simple diffusion to enterocyte -> Intracellular resynthesis into triglyceride
[T/F]
Lipids have brush border digestion
F
How many g/day of Carbohydrates should be consumed?
250-800g/day
Luminal Digestion Enzymes Components
Ptyalin: 20-40%
Pancreatic Amylase: 60-80%
Enzyme found in the mouth
Salivary alpha-amylase
% of starch digestion in the mouth
20%
Enzyme found in the Duodenum
Pancreatic alpha-amylase
What breaks down disaccharides in the duodenum?
Brush Borders
How are Glucose and Galactose transported?
Enter through the apical side together with Na+ through SGLT-1 (Sodium Glucose Transporter 1)
How many sodium ions to one glucose or galactose?
2 Na+ : 1 GLU/GAL
How is Fructose absorbed?
GLUT-5
How do Glucose, Galactose, and Fructose pass the basolateral side to the interstitial space?
GLUT-2 Facilitated Diffusion
Order of Absorbability of Monosaccharides
Galactose Glucose Fructose Mannose Xylose Arabinose
Daily Dietary Protein Requirement
0.5-0.7g/kg
[Endogenous Proteins]
Amount per day?
Where are they from?
30-40g/day
From secretory proteins and desquamated cells
Sources of the protein in stools
[Exogenous Proteins]
Amount per day?
Where are they from?
70-100g/day
Dietary Proteins
Where does protein digestion start?
Stomach
Proteins are acted upon by _____ to produce _______?
Pepsin
Proteoses, peptones, and polypeptides
Proteoses, peptones, and polypeptides are acted upon by ______ to produce _______?
Trypsin, chymotrypsin, carboxypolypeptidase, proelastase
Polypeptides + Amino Acids
Polypeptides + Amino Acids are acted upon by _____ to produce ______
Peptidases
Amino Acids
Complete digestion of food requires?
Pancreatic and Brush Border Enzymes
What activates Trypsin?
Enterokinase
Where are enterokinases produced?
Duodenum and Jejunum
What is the transport protein for di/tripeptides?
PepT1
Common Cause of Fat Malabsorption
Obstruction of common bile duct or tumor in the pancreatic head/bile duct
Function: Colipase
Anchors lipase displayed by bile acids
Phospholipids are acted upon by ______ to become ______ and ______
Phospholpase A2
Fatty Acids and Lysolecithin
Cholesterol Esters (CE) are acted upon by _______ to become _______ and ________
Cholesterol Esterase
Fatty Acids and Cholesterol
Gastric Lipase is responsible for what % of fat digestion?
15%
Can chylomicrons enter the capillary?
No, because they are too large.
Only Medium-Chain FAs can go into capillaries
Define: Steatorrhea
Failure of fat absorption due to the lack of bile
Where is sodium mainly absorbed?
Small Intestine and Colon
Where are vitamins absorbed?
Proximal Portion of the Small Intestine