Digestion and Absorption Overview
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Questions and Answers

Where does protein digestion begin?

  • In the small intestine
  • In the large intestine
  • In the stomach (correct)
  • In the mouth

What type of bond does pepsin primarily break down during protein digestion?

  • Ionic bonds
  • Disulfide bonds
  • Peptide bonds (correct)
  • Hydrogen bonds

Which substance is secreted in the stomach to aid protein digestion?

  • Bile
  • Pepsin (correct)
  • Lactase
  • Amylase

What role does HCl play in protein digestion?

<p>It activates pepsinogen to pepsin. (D)</p> Signup and view all the answers

What is the main site of iron absorption in the digestive system?

<p>Upper small intestine (A)</p> Signup and view all the answers

Which form of iron is more readily absorbed?

<p>Fe++ (ferrous iron) (A)</p> Signup and view all the answers

Why is protein digestion limited in the stomach?

<p>Pepsin and HCl cannot attack the interior of the food mass. (A)</p> Signup and view all the answers

Which of the following factors increases calcium absorption?

<p>Vitamin D (A)</p> Signup and view all the answers

Which of the following is NOT directly involved in iron absorption?

<p>Parathyroid hormone (B)</p> Signup and view all the answers

Which of these statements is TRUE about iron absorption?

<p>Iron absorption is increased by factors like gastric acid and certain proteins. (B)</p> Signup and view all the answers

What is the primary function of Brush border enzymes located at the surface of microvilli?

<p>Final digestion of carbohydrates and proteins (D)</p> Signup and view all the answers

Where are Brush border enzymes predominantly found?

<p>On the luminal membrane of microvilli (B)</p> Signup and view all the answers

Which of the following statements best describes Brush border enzymes?

<p>They are involved in the final digestion process (A)</p> Signup and view all the answers

What types of macromolecules are specifically aided by Brush border enzymes during digestion?

<p>Carbohydrates and proteins (C)</p> Signup and view all the answers

Which of the following is NOT a role of Brush border enzymes?

<p>Hormonal regulation of digestion (B)</p> Signup and view all the answers

What is the role of the bush border enzymes mentioned?

<p>They initiate the breakdown process. (D)</p> Signup and view all the answers

What does the term 'awaiting yet further breakdown' suggest about the substances mentioned?

<p>They require additional processing. (D)</p> Signup and view all the answers

Which of the following best describes the timing of the action of the bush border enzymes?

<p>They are activated in response to further breakdown requirements. (D)</p> Signup and view all the answers

What implication does the use of the word 'yet' in 'awaiting yet further breakdown' have about the process?

<p>There have been multiple breakdowns already. (C)</p> Signup and view all the answers

What can be inferred about the state of the substances needing breakdown?

<p>They are partially processed and need enzymes for completion. (A)</p> Signup and view all the answers

What form does food take when it is being acted upon by enzymes like pepsin?

<p>Semisolid mass (B)</p> Signup and view all the answers

At what pH level does pepsin become inactivated?

<p>pH 5 (D)</p> Signup and view all the answers

Why is the exterior of the semisolid mass important for enzyme action?

<p>Only the exterior is exposed to enzymes. (D)</p> Signup and view all the answers

Which pH level would be optimal for the function of pepsin?

<p>pH 2 (D)</p> Signup and view all the answers

What happens to pepsin when the pH rises above 5?

<p>It undergoes denaturation. (D)</p> Signup and view all the answers

What process is primarily responsible for water movement into epithelial cells?

<p>Transport of Na+ ions into the cell (A)</p> Signup and view all the answers

How does the tight junctions contribute to water absorption in epithelial cells?

<p>They facilitate water flow specifically into cells (C)</p> Signup and view all the answers

Which ion's transport is directly associated with water absorption in epithelial cells?

<p>Na+ (D)</p> Signup and view all the answers

What role do epithelial cells play concerning water and electrolyte balance?

<p>They help absorb both water and electrolytes (C)</p> Signup and view all the answers

Which of the following statements is false regarding water absorption mechanisms in epithelial cells?

<p>Tight junctions inhibit water movement into cells. (B)</p> Signup and view all the answers

Flashcards

Bush Border Enzymes

Enzymes that play a critical role in breaking down substances within the body.

Breakdown

The process of breaking down large molecules into smaller ones.

Carried

The process of carrying out tasks or processes.

Microvilli

Tiny finger-like projections on the surface of cells, increasing surface area for absorption.

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Luminal Membrane

The outer layer of a cell that faces the outside environment.

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Digestion

The process of breaking down large food molecules into smaller ones.

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Macromolecules

Carbohydrates and proteins are examples of these.

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Protein Digestion Start

Protein digestion begins in the stomach, where pepsin and hydrochloric acid (HCl) break down peptide bonds between amino acids, resulting in large polypeptides.

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Pepsin

Pepsin is an enzyme secreted by the stomach that helps break down proteins into smaller units called polypeptides.

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Hydrochloric Acid (HCl)

Hydrochloric acid (HCl) is produced by the stomach and aids in protein digestion. It creates an acidic environment optimal for pepsin activity.

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Peptide Bonds

Peptide bonds are the chemical links that hold amino acids together in a protein.

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Water absorption in the gut

Movement of water from the outside of the epithelial cell to the inside, through the tight junctions.

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Polypeptides

Large polypeptides are the partially digested proteins resulting from the initial breakdown in the stomach. They will be further broken down in the small intestine.

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Sodium transport (Na+)

The process of transporting sodium ions across the cell membrane.

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Tight junctions

A type of cell junction that limits the passage of substances between cells.

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Basolateral membrane

The side of the epithelial cell facing the bloodstream.

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Cell membrane

A membrane that determines what enters and exits a cell.

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Chyme

The semi-solid mass of food in the stomach, with only the exterior exposed to digestive enzymes.

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Pepsin's Optimal pH

The enzyme pepsin works best in a highly acidic environment, with a pH level between 2 and 3.

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Pepsin Deactivation

Pepsin's activity is significantly reduced and eventually stopped when the pH rises above 5.

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Surface Digestion

The outer layer of the food mass in the stomach is the only part exposed to digestive enzymes.

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Stomach Churning

The stomach's churning action helps expose more of the food mass to digestive enzymes.

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Calcium Absorption

Calcium absorption is increased by vitamin D and parathyroid hormone, promoting bone health and mineral balance.

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Iron Absorption Location

Iron absorption primarily occurs in the upper part of the small intestine.

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Iron Absorption: Fe++ vs Fe+++

Ferrous iron (Fe++) is more easily absorbed by the body than ferric iron (Fe+++).

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Role of Vitamin D & PTH in Calcium Absorption

Vitamin D and parathyroid hormone increase calcium absorption in the body.

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Importance of Iron Absorption

Iron absorption is crucial for red blood cell production and oxygen transport.

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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!

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