Digestive System Functions

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Questions and Answers

What is the primary role of the digestive system?

  • To mechanically break down food only
  • To break down food into absorbable molecules and facilitate absorption (correct)
  • To transport food directly to the bloodstream
  • To absorb liquids without processing food

Where does the majority of nutrient absorption occur in the digestive system?

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

What initiates the enzymatic digestion of proteins in the digestive system?

  • Brush-border enzymes in the small intestine
  • Salivary enzymes in the oral cavity
  • Enzymes secreted by the pancreas
  • Acid secretion in the stomach (correct)

Which enzyme converts trypsinogen to its active form?

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

What are brush-border enzymes?

<p>Enzymes attached to the surface of epithelial cells in the digestive tract (D)</p> Signup and view all the answers

What happens to carbohydrate digestion when food reaches the stomach?

<p>It stops due to denaturation of the enzyme (C)</p> Signup and view all the answers

Which food molecule is primarily broken down into amino acids?

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

Which of the following statements about pancreatic proenzymes is true?

<p>They remain inactive until released into the digestive tract (B)</p> Signup and view all the answers

What type of enzyme does the pancreas secrete to help in carbohydrate digestion?

<p>Pancreatic amylase (D)</p> Signup and view all the answers

Which monosaccharides result from the digestion of carbohydrates by brush-border enzymes?

<p>Glucose, fructose, galactose (A)</p> Signup and view all the answers

How are triglycerides and long-chain fatty acids processed in the small intestine?

<p>Broken down into monoglycerides and free fatty acids (B)</p> Signup and view all the answers

What is the purpose of brush-border digestive enzymes like sucrase, maltase, and lactase?

<p>To digest carbohydrates into monosaccharides (B)</p> Signup and view all the answers

What happens to the chylomicrons after they are assembled in the epithelial cells?

<p>They are exocytosed into interstitial fluid (A)</p> Signup and view all the answers

How are amino acids absorbed in the small intestine?

<p>They are absorbed in the form of di- and tripeptides (B), They diffuse across the epithelial cells (D)</p> Signup and view all the answers

Which of the following is NOT a function of lipids in the body?

<p>Provide fiber (C)</p> Signup and view all the answers

The final absorption of nutrients in the small intestine primarily occurs at which cellular structure?

<p>Epithelial cells (A)</p> Signup and view all the answers

Flashcards

Pancreatic amylase

An enzyme that continues carbohydrate digestion

Brush-border enzymes

Digestive enzymes on the surface of small intestine cells

Sucrase, Maltase, Lactase

Brush-border enzymes that digest disaccharides (into monosaccharides)

Monosaccharides absorption

Glucose, fructose, and galactose enter the bloodstream from the small intestine

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Protein digestion products

Amino acids, dipeptides, and tripeptides are absorbed into the bloodstream

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Chylomicron formation

Fat molecules (monoglycerides/free fatty acids) are packaged with cholesterol & proteins in the small intestine

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Chylomicron transport

Fat particles enter the lymph system, then the bloodstream

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Nutrient fate

The cell's metabolic state determines how absorbed nutrients are used

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Digestion in the Oral Cavity

Mechanical and enzymatic breakdown of food, starting with chewing and saliva secretion containing enzymes for carbs and fats.

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Digestion in the Stomach

Enzymatic digestion of proteins begins, and some fat digestion continues, with acid secretion aiding protein breakdown. Carb digestion stops.

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Small Intestine Digestion

Primary site for digestion and absorption of nutrients (like glucose) in the digestive tract; most of the enzymes are from the pancreas.

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Pancreatic Proenzymes

Inactive enzymes secreted by the pancreas that are activated later in the digestive tract to prevent self-digestion.

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Trypsinogen Activation

Trypsinogen (a proenzyme) is activated into trypsin by enteropeptidase, an enzyme on the small intestine cell membrane.

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Trypsin Action

Trypsin, activated from trypsinogen, further digests proteins and activates other pancreatic proenzymes.

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Types of ingested food

Carbohydrates, proteins, and fats form the main types of ingested molecules that must be broken down, digested and absorbed.

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Study Notes

Digestive System Functions

  • The digestive system breaks down food into absorbable molecules.
  • It absorbs these molecules for use by the body.
  • The main food molecules are carbohydrates, proteins, and fats.

Digestion in the Oral Cavity

  • Digestion begins in the mouth.
  • Food is chewed, and enzymes in saliva start breaking down carbohydrates and fats.
  • The food is swallowed, passing to the esophagus.

Stomach Digestion

  • Stomach acid denatures enzymes that began digesting carbohydrates.
  • Protein digestion begins in the stomach.
  • Fat digestion continues.

Digestion in the Small Intestine

  • Most digestion and absorption of nutrients occur in the small intestine.
  • Enzymes from the pancreas are crucial for this process.
  • Many pancreatic enzymes are initially inactive (proenzymes).
  • Proenzymes are activated in the small intestine.
  • An example of a pancreatic proenzyme is trypsinogen, which becomes trypsin.
  • This conversion is catalyzed by enteropeptidase, an enzyme attached to the cell membrane of small intestine epithelial cells.
  • Brush-border enzymes (on the surface of the epithelial cells) carry out further digestion of carbohydrates, proteins, and fats. Examples are sucrase, maltase, lactase.
  • Carbohydrate digestion products (monosaccharides) are absorbed into the bloodstream.
  • Protein digestion products (amino acids) are absorbed into the blood.
  • The absorbed triglycerides combine with cholesterol and proteins to form chylomicrons.
  • Chylomicrons are absorbed into lymph vessels (lacteals).
  • Chylomicrons enter the venous circulation through the thoracic ducts.

Further processing

  • The absorbed cholesterol is also transported in the intestines and is processed in cells

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