Digestion and Absorption Flashcards
(36 cards)
What is the importance of the Villous Lining of the Small Intestine?
- Allows for absorption
2. Houses Brush Border Enzymes that perform the final digestion of Proteins and Carbs
Brush Border Enzymes are responsible for final digestion of what materials?
- Proteins
2. Carbohydrates
What is the important Cl- Channel on the Villi of the Small Intestine?
The CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) which is stimulated by Secretin to secrete Cl- into the gut which is followed by Na and H2O creating a good buffer
What are the majority of the Carbs we ingest?
- Starches
2. Dissacharides (Sucrose and Lactose)
What monosaccharides make up Sucrose?
- Glucose
2. Fructose
What monosaccharides make up Lactose?
- Glucose
2. Galactose
Where does Starch Digestion start?
IN THE MOUTH
Salivary Alpha-Amylase is activated by Cl- to break Starches down into Malto-Oligosaccharides (Maltose and Isomaltose)
Where can Starch be digested?
- Mouth (25-30%)
2. Small Intestine (70-75%)
How is Starch Digested in the Small Intestine?
- Pancreatic Alpha-Amylase enzymes in the Duodenum break down the Starches into Malto-Oligosaccharides (Maltose and Isomaltose)
- Brush Border enzymes located in the Glycocalyx of the Villus lining in the Small Intestine take the Oligossacharides (Maltose and Isomaltose) and Disaccharides (Sucrose and Lactose) and break them down into Monosaccharides to be absorbed
Name the Brush Border Enzymes of the Small Intestines and the sugars they produce:
- Isomaltase (Glucose)
- Maltase (Glucose)
- Lactase (Glucose and Galactose)
- Sucrase (Glucose and Fructose)
What can undigested Carbohydrates in the Body cause?
- Diarrhea (because sugars are isoosmotic and draw water into the GI tract)
- Cramping and Gas (provides food for bacteria)
How do Monosaccharides enter the Enterocytes of the Small Intestine?
INSULIN-INDEPENDENT TRANSPORTERS
- SGLT-1- Glucose and Galactose enter via Secondary Active Transport with Na
- GLUT-5- Primary Active Transporter that is a Fructose Carrier
Does Glucose increase or decrease water and electrolyte reabsorption of the Small Intestine? How?
Glucose INCREASES Water and Electrolyte reabsorption in the Small Intestine because:
- Enters Enterocytes with Na via SGLT-1 (Na draws water and solute)
- Water follows Glucose as it is ingested and also draws solute with it
Assuming no digestive issues, what is the most easily digested compound that we ingest?
A. Lipids/Fats
B. Proteins
C. Carbohydrates
C. Carbohydrates
AS LONG AS THE AMYLASES AND BRUSH BORDER ENZYMES ARE ALL FUNCTIONAL
What are Olestra and Sucralose?
Carbohydrates that are UNDIGESTIBLE and cause cramps, gas, bloating, and diarrhea if ingested in large quantities because they CANNOT be absorbed leading to Water staying in the GI tract AND they provide food for bacteria
Where does Protein Digestion start? By what enzymes?
Protein Digestion starts in the stomach:
- Pepsinogens are secreted into the stomach as inactive Zymogens
- Pepsinogens are activated by the low pH of the stomach into Pepsin
- Pepsin cleaves Proteins into Oligopeptides
Where does Protein Digestion happen in the body? What enzymes are used? What percentage of the Proteins are hydrolyzed in each place?
- Stomach- Pepsins cleave 25-30% of the Proteins into Oligopeptides
- Small Intestine- Pancreatic Proteases cleave 70-75% of Proteins into Oligopeptides
- Cytoplasmic Peptidases inside of the Enterocytes break down the absorbed Di- and Tri-Peptides into Amino Acids
NOTE: Brush Border Proteases hydrolyze the Oligopeptides into Di- and Tri-Peptides and Amino Acids
What stimulates the release of Pancreatic Enzymes into the Duodenum?
CCK
What stimulates the release of Pancreatic and Intestinal Buffers?
Secretin (increases the pH of the Acidic Chyme)
What are the Pancreatic Proteases released into the Duodenum due to CCK stimulation? How are they activated?
The Pancreatic Proteases are:
- Trypsinogen
- Chymotrypsinogen
- Pre-Colipase
- Proelasatase
Enterokinase (EK) on the Brush Border activates Trypsin and Trypsin activates the others and also self-activates itself
What kinds of Proteins are absorbed in the Small Intestines and how?
- Oligopeptides (created by Gastric and Pancreatic Proteases) are broken down by Brush Border Proteases into Di- and Tri-Peptides and Amino Acids
- Di- and Tri-Peptides AND Amino Acids are absorbed into Enterocytes via various transporters
What part of digested Proteins is able to leave Enterocytes and enter the bloodstream?
Amino Acids are the only part of digested Proteins able to leave Enterocytes and enter the bloodstream:
CYTOPLASMIC PEPTIDASES break down the absorbed Di- and Tri-Peptides into Amino Acids
What happens to Amino Acids in the Liver?
- Shuttled via Lipoproteins to places needed
- Extra AAs are Deaminated to NH3+ which combines with CO2 to make Urea
- Synthesize 90% of Plasma Proteins
Where does Lipid Digestion start? By what enzymes?
The MOUTH via Lingual Lipase (helps with the flavor of food)
