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Questions and Answers
Where does protein digestion begin?
Where does protein digestion begin?
What type of bond does pepsin primarily break down during protein digestion?
What type of bond does pepsin primarily break down during protein digestion?
Which substance is secreted in the stomach to aid protein digestion?
Which substance is secreted in the stomach to aid protein digestion?
What role does HCl play in protein digestion?
What role does HCl play in protein digestion?
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What is the main site of iron absorption in the digestive system?
What is the main site of iron absorption in the digestive system?
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Which form of iron is more readily absorbed?
Which form of iron is more readily absorbed?
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Why is protein digestion limited in the stomach?
Why is protein digestion limited in the stomach?
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Which of the following factors increases calcium absorption?
Which of the following factors increases calcium absorption?
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Which of the following is NOT directly involved in iron absorption?
Which of the following is NOT directly involved in iron absorption?
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Which of these statements is TRUE about iron absorption?
Which of these statements is TRUE about iron absorption?
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What is the primary function of Brush border enzymes located at the surface of microvilli?
What is the primary function of Brush border enzymes located at the surface of microvilli?
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Where are Brush border enzymes predominantly found?
Where are Brush border enzymes predominantly found?
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Which of the following statements best describes Brush border enzymes?
Which of the following statements best describes Brush border enzymes?
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What types of macromolecules are specifically aided by Brush border enzymes during digestion?
What types of macromolecules are specifically aided by Brush border enzymes during digestion?
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Which of the following is NOT a role of Brush border enzymes?
Which of the following is NOT a role of Brush border enzymes?
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What is the role of the bush border enzymes mentioned?
What is the role of the bush border enzymes mentioned?
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What does the term 'awaiting yet further breakdown' suggest about the substances mentioned?
What does the term 'awaiting yet further breakdown' suggest about the substances mentioned?
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Which of the following best describes the timing of the action of the bush border enzymes?
Which of the following best describes the timing of the action of the bush border enzymes?
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What implication does the use of the word 'yet' in 'awaiting yet further breakdown' have about the process?
What implication does the use of the word 'yet' in 'awaiting yet further breakdown' have about the process?
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What can be inferred about the state of the substances needing breakdown?
What can be inferred about the state of the substances needing breakdown?
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What form does food take when it is being acted upon by enzymes like pepsin?
What form does food take when it is being acted upon by enzymes like pepsin?
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At what pH level does pepsin become inactivated?
At what pH level does pepsin become inactivated?
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Why is the exterior of the semisolid mass important for enzyme action?
Why is the exterior of the semisolid mass important for enzyme action?
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Which pH level would be optimal for the function of pepsin?
Which pH level would be optimal for the function of pepsin?
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What happens to pepsin when the pH rises above 5?
What happens to pepsin when the pH rises above 5?
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What process is primarily responsible for water movement into epithelial cells?
What process is primarily responsible for water movement into epithelial cells?
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How does the tight junctions contribute to water absorption in epithelial cells?
How does the tight junctions contribute to water absorption in epithelial cells?
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Which ion's transport is directly associated with water absorption in epithelial cells?
Which ion's transport is directly associated with water absorption in epithelial cells?
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What role do epithelial cells play concerning water and electrolyte balance?
What role do epithelial cells play concerning water and electrolyte balance?
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Which of the following statements is false regarding water absorption mechanisms in epithelial cells?
Which of the following statements is false regarding water absorption mechanisms in epithelial cells?
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Study Notes
Digestion and Absorption
- Digestion involves enzymes catalyzing carbohydrates, proteins, and lipids.
- Absorption is done by specialized epithelial cells.
- Most absorption occurs in the small intestine, with some in the stomach.
- The esophagus' primary function is transporting food.
- Most nutrients are absorbed before reaching the ileum.
- The colon absorbs water and electrolytes.
- The small intestine's structure increases nutrient absorption.
- Mucosal folds (Kerckring folds) increase surface area threefold.
- Villi increase surface area tenfold.
- Microvilli increase surface area twentyfold.
- Total surface area increase is approximately 600-fold.
Carbohydrate Digestion and Absorption
- Carbohydrates are ingested as starch, sucrose, lactose, and cellulose.
- Cellulose isn't digested.
- Digestion begins in the oral cavity with salivary amylase (ptyalin).
- Amylase hydrolyzes 1-4 alpha glycosidic bonds in starch.
- Starch is partially broken down into smaller glucose polymers and alpha-limit dextrins.
- Pancreatic amylase further digests starch in the small intestine.
- Remaining starch is broken down into maltose and maltotriose.
- Brush border enzymes (e.g., lactase, sucrase, maltase) hydrolyze disaccharides into monosaccharides (glucose, galactose, fructose).
- Glucose, fructose, and galactose are absorbed.
Protein Digestion and Absorption
- Protein digestion begins in the stomach with pepsin and HCl.
- Pepsin hydrolyzes peptide bonds in proteins
- Pepsin is inactive at pH 5 and above.
- Proteolytic enzymes in the small intestine (e.g., endopeptidases and exopeptidases) further digest polypeptides.
- Brush border enzymes (peptidases) convert peptides to amino acids.
- Di- and tripeptides are transported into cells by carrier-mediated transport.
- Amino acids are transported into cells using Na+ dependent carriers.
Lipid Digestion and Absorption
- Bile is important for lipid digestion.
- Bile is secreted by the liver.
- Bile salts are amphipathic.
- Bile salts form micelles, which dissolve fats.
- Pancreatic lipase and colipase hydrolyze triacylglycerols into monoglycerides and free fatty acids.
- Micelles transport monoglycerides and free fatty acids to the intestinal cells.
- Monoglycerides and free fatty acids combine to form triglycerides within the cells
- Triglycerides combine with cholesterol, phospholipids, and proteins to form chylomicrons.
- Chylomicrons are expelled from the cells by exocytosis and enter the lymphatic system.
- Some glycerol and short-chain fatty acids are absorbed directly into blood capillaries.
Water and Electrolyte Absorption
- Water is absorbed passively, following Na+ transport.
- Sodium is actively transported.
- Chloride is absorbed passively.
- Potassium is absorbed passively or actively, depending on location.
- Calcium absorption is active, facilitated by vitamin D and parathyroid hormone.
Iron Absorption
- Ferrous iron (Fe++) is more readily absorbed than ferric iron (Fe+++).
- Acidic pH and Vitamin C enhance iron absorption.
- Iron is absorbed through ferritin and endocytosis.
- Excess iron is prevented from entering the bloodstream by a mucosal block.
Vitamin Absorption
- Water-soluble vitamins are absorbed passively, except some, (e.g., Vitamin B12).
- Vitamin B12 absorption requires intrinsic factor.
- Fat-soluble vitamins follow the same pathway as lipids.
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Description
This quiz explores the processes of digestion and absorption with a focus on carbohydrates. You'll learn about enzyme functions, nutrient absorption locations, and the anatomy involved in maximizing surface area for nutrient uptake. Test your understanding of how the digestive system processes food!
