DIGESTION Flashcards
- If lipids provide much more energy than carbohydrates why did we evolve using both food
sources?
Lipids and carbs evolved due AVAILABILITY. If you only had one of these two being able to only metabolize fat not useful when you on,y eat fruit. Likewise if you hunt and kill animal for food, only digesting carbs not very useful.
lipids can on,y be used when oxygen is available. While carbs can be used for either aerobic or anaerobic conditions (during intense workouts, carbs used for more energy)
*Understand where and how the digestive enzymes work, for proteins, carbohydrates and
lipids.
proteins- digested to amino acids by proteolytic enzymes (proteases) secreted by stomach and pancreas
-polysaccharides (carbs) like starch are cleaved into monosaccharides by alpha-amylase from the pancreas and lesser amount of Saliva.
-Lipids converted to fatty acids by lipases secreted by the pancreas.
all the digestive enzymes are hydrolases (cleave their substrates by adding water).
*How does omeprazole work?
Omeprazole is a drug that treats GERD (gastroesophageal reflux disease), acid reflux as it inhibits K+/H+ ATPase (decreases amount of acid in the stomach).
*How does glycocholate work? What is the added issue with digestion of lipids?
Glycocholate is one of the bile salts that faciliates lipid digestion in the intestine.
Bile salts are amphiphatic molecules synthesized from cholesterol in the liver and secreted from gallbladder in response to CCK. The salts insert themselves into lipids making the Triacylglycerols more readily digestible.
*Understand what celiac disease is and what the causes are.
Celiac disease (gluten enteropathy)- an intestinal inflammatory disorder that results because of susceptible individuals are unable to digest certain proteins from wheat, rye and barley. These proteins are called GLUTEN and are rich in Glutamine and proline. The gluten-derived peptides generate an inflammatory response that damages the intestinal lining and impairs nutrient absorption.
What is Digestion?
Digestion- set of biochemical reactions that convert food into molecules further broken down for useful energy and biosynthetic building blocks.
How is a meal digested?
The components of meal (PROTEINS, LIPIDS and POLYSACCHARIDES) must be degraded into small molecules for absorption and transport.
Diverse set of hydrolytic enzymes create this degradation.
Where does Digestion begin?
Digestion begins in the MOUTH, where food is mechanically degraded. Chewing converts the meal into slurry that is more readily attacked by hydrolytic enzymes.
Describe the digestive enzymes in the pancreas, and how they differ in their active form vs inactive form.
The enzymes of pancreas are secreted as inactive precursors called proenzymes or zymogens
ENTEROPEPTIDASE- secreted by intestinal cells, converts inactive TRYPSINOGEN into active Trypsin
TRYPSIN will then activate other proenzymes.
List the different forms of Gastric and pancreatic enzymes in their inactive and active forms.
- Stomach; inactive form: pepsinogen Active: Pepsin. Pancreas enzymes: 1. Inactive form: chymotrypsinogen, active: chymotrypsin
- inactive: trypsinogen; active: Trypsin
- inactive: procarboxypeptidase active: carboxypeptidase
- inactive: proelastase active: elastase
most breakdowns of complex molecules occur in intestines
Describe how proteins are digested in the stomach. What generates the kind of environment of stomach?
How can the stomach environment be an issue, and what is the treatment used for it?
The highly acidic environment of stomach denatures proteins, making them more susceptible to digestion by proteolytic enzymes like pepsin (stomach enzyme)
acid environment of stomach is generated by K+/H+ ATPase.
Excessive acid generation may result in gastroesophageal reflux disease (GERD), where stomach acid leaks back to esophagus
GERD can be treated with inhibitors of K+/H+ ATPase like Omeprazole (converted to sulfenic acid, then sulfonamide).
How is food digestion further continued from the stomach to the intestine
movement of food from stomach to intestine stimulates the secretion of two key hormones by cells of small intestine:
- SECRETIN causes release of sodium bicarbonate, which neutralizes the stomach.
- CHOLECYSTOKININ (CCK)- stimulates the release of digestive enzymes from the pancreas as well as secretion of bile salts from gallbladder.
What are the initial digestion products of intestine-
Secretin and CCK
How are proteins then digested in the intestine? what are peptidases?
proteins are digested into amino acids and small oligopeptides. The amino acids are absorbed by transporters.
-peptidases on the surface of the intestinal cells cleave the oligopeptides into di and tripeptides which are transported into intestinal cells and degraded into amino acids
amino acids are then released into blood by antiporters.
Describe how carbs are digested and which enzymes are involved.
The primary source of carbohydrates is starch.
Several enzymes participated in carbohydrate digestion:
- Alpha-Amylase initiates digestion by cleaving alpha-1,4 bonds but NOT alpha-1,6 bonds.
-other enzymes like maltase, alpha-glucosidase (digest, maltriose, maltose) and alpha-dextranase(digest limit dextrin) complete the digestion.
-Sucrose (fructose and glucose) and lactose (milk sugar), two common disaccharides are digested by sucrase and lactase enzymes.
Glucose and galactose are transported into intestine by Na+ Glucose linked transporter (secondary) and GLUT 5 transporter allows entry of fructose.
