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Questions and Answers

What is the primary route by which absorbed protein products exit the villous epithelial cell and enter the blood?

  • Through the basolateral membrane
  • As dipeptides, tripeptides, or tetrapeptides
  • As individual amino acids (correct)
  • Via luminal proteases

    • How are substantial amounts of protein absorbed from the intestinal lumen?

  • Through the basolateral membrane
  • As dipeptides, tripeptides, or tetrapeptides (correct)
  • By luminal proteases
  • As intact proteins

    • What is the general consensus about the number of distinct transport systems present at the apical membrane for amino acids?

  • Only one distinct transport system
  • Three distinct transport systems
  • Seven distinct transport systems (correct)
  • At least five distinct transport systems

    • How do amino acids exit enterocytes into the blood during protein assimilation?

    <p>Through Na+-dependent transporters</p> Signup and view all the answers

    What mediates the exit of amino acids from enterocytes into the blood during protein assimilation?

    <p>Basolateral membrane transporters</p> Signup and view all the answers

    Which process involves hydrolyzing proteins to peptides and then to amino acids before absorption?

    <p>Protein Digestion</p> Signup and view all the answers

    What is the primary function of luminal enzymes in protein digestion?

    <p>Digesting Proteins to Peptides</p> Signup and view all the answers

    Which transporter is responsible for the exit of monosaccharides across the basolateral membrane?

    <p>GLUT2</p> Signup and view all the answers

    What is the primary mechanism of fructose absorption when SGLT1 cannot carry it?

    <p>Facilitated Diffusion through GLUT5</p> Signup and view all the answers

    Which step is essential for proteins to be absorbed by enterocytes?

    <p>Digestion into Amino Acids</p> Signup and view all the answers

    How are proteins absorbed when luminal enzymes digest proteins to peptides that are taken up as oligopeptides?

    <p>As Oligopeptides by Enterocytes</p> Signup and view all the answers

    What type of proteins are essential amino acids derived from?

    <p>Digested proteins</p> Signup and view all the answers

    How are gastric and pancreatic proteases different from digestive enzymes for carbohydrates and lipids?

    <p>They require conversion to their active form for digestion to occur.</p> Signup and view all the answers

    During what period does the absorption of whole protein by apical pinocytosis occur?

    <p>During the neonatal period</p> Signup and view all the answers

    What is the uncertainty in adults regarding the absorption of intact proteins?

    <p>The cellular route by which these substances are absorbed</p> Signup and view all the answers

    What is the fate of virtually all absorbed protein products as they exit the villous epithelial cell?

    <p>They exit as amino acids</p> Signup and view all the answers

    How does the movement of amino acids across the basolateral membrane occur?

    <p>Bidirectionally through one or more amino acid transporters</p> Signup and view all the answers

    What type of transporters are responsible for amino acid exit from enterocytes into the blood during protein assimilation?

    <p>Na+-dependent transporters</p> Signup and view all the answers

    Name the 3 Accessory glands

    <p>Pancreas, Liver, Salivary glands</p> Signup and view all the answers

    Order of digestion

    <p>Mouth = 1 Stomach = 2 Small Intestine = 3 Large Intestine = 4</p> Signup and view all the answers

    Which one is NOT a monosaaccharide

    <p>Sucrose</p> Signup and view all the answers

    Which one is NOT a Polysaccharide

    <p>Maltose</p> Signup and view all the answers

    The small intestine can directly absorb monomers but not polymers

    <p>True</p> Signup and view all the answers

    What happens to CHO during intraluminal hydrolysis?

    <p>starch to oligosaccharides</p> Signup and view all the answers

    The products of starch hydrolysis are monosaccharides

    <p>False</p> Signup and view all the answers

    Disaccharides can be absorbed by the SI

    <p>False</p> Signup and view all the answers

    What happens in membrane digestion of CHO

    <p>Oligosaccharides to monosaccharides by brush border disaccharidases</p> Signup and view all the answers

    Glucose, Fructose, and Galactose are all absorbed the same way

    <p>False</p> Signup and view all the answers

    What transport process does Glucose and Galactose undergo?

    <p>Active transport</p> Signup and view all the answers

    All 3 monosaccharides use the same facilitated sugar transporter (GLUT2) to exit the basolateral membrane

    <p>True</p> Signup and view all the answers

    Protein has to be digested into what, before being taken up by the enterocytes

    <p>Oligopeptides and amino acids</p> Signup and view all the answers

    Describe the 4 digestion-absorption pathways of protein in the SI

    <p>3 of them involve protein hydrolysis into peptides and then into AAs. In these 3 pathways, the location where peptides are broken into AAs is different. Luminal enzymes, or proteases break down peptides in the SI, or peptides can be broken down at the brush border before being aborbed, and finally peptides get absorbed by the enterocytes and are broken down to AAs intracellularly before relased into blood. The 4th, and rare pathway is similar to the last, except the peptides never get broken down into AAs, and instead released into blood as peptides</p> Signup and view all the answers

    What is the key step before lipids can be digested?

    <p>The transformation of ingested solid fat and oil masses into an emulsion of fine oil droplets in water</p> Signup and view all the answers

    Only 15% of lipid digestion occurs in the stomach

    <p>True</p> Signup and view all the answers

    Why does most of lipid digestion happen in the SI?

    <p>Gastric and lingual lipases (that digest fats) are inactive in the stomach because of the present pancreatic proteases and they are inactive at a neutral pH</p> Signup and view all the answers

    What enzyme completes lipid hydrolysis, and what is it aided by?

    <p>Pancreatic lipase, and aided by bile salts</p> Signup and view all the answers

    What happens when the fatty acids (generated from lipid hydrolysis in the stomach) reach the duodenum?

    <p>They trigger the release of CCK and GIP from the duodenal mucosa</p> Signup and view all the answers

    What is the role of CCK and how is it released?

    <p>It is released when fatty acids from the stomach reach the duodenum. It stimulates the flow of bile into the duodenum and the secretion of pancreatic enzymes</p> Signup and view all the answers

    What form do lipids diffuse across the enterocytes as?

    <p>Micelles and monomers</p> Signup and view all the answers

    What are the 2 steps to CHO digestion?

    <p>Intraluminal hydrolysis and membrane digestion</p> Signup and view all the answers

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