Chapter 26 | GIT Digestion & Absorption
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Questions and Answers

Where does the digestion of proteins, fats, and complex carbohydrates primarily occur?

  • Salivary glands
  • Liver
  • Small intestine (correct)
  • Stomach

    • Which part of the pancreas is responsible for attacking carbohydrates, proteins, lipids, DNA, and RNA?

  • Endocrine portion
  • Islets of Langerhans
  • Exocrine portion (correct)
  • Acinar cells

    • What aids in the digestive process along with enzymes in the small intestine?

  • Hydrochloric acid from the liver
  • Saliva from the salivary glands
  • Mucus secretion
  • Bile from the pancreas (correct)

    • Which gland secretes enzymes that attack carbohydrates and fats, in addition to proteins?

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

    In which part of the gastrointestinal system do vitamins, minerals, and water cross the mucosa and get absorbed into the body?

    <p>Small intestine</p> Signup and view all the answers

    Which organ secretes hydrochloric acid that aids in digestion alongside enzymes?

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

    What are the end products of α-amylase digestion of polysaccharides in the small intestine?

    <p>Maltose, maltotriose, and α-limit dextrins</p> Signup and view all the answers

    Where are the oligosaccharidases responsible for further digestion of starch derivatives located?

    <p>In the brush border of small intestinal epithelial cells</p> Signup and view all the answers

    Which enzyme is mainly responsible for hydrolysis of 1:6α linkages?

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

    How is sucrase formed in the small intestine?

    <p>By pancreatic proteases hydrolyzing a glycoprotein chain into sucrase</p> Signup and view all the answers

    What is the result of lactase enzyme activity?

    <p>Glucose and galactose</p> Signup and view all the answers

    What symptoms may arise due to a deficiency in brush border oligosaccharidases?

    <p>Diarrhea, bloating, and flatulence</p> Signup and view all the answers

    What are symptoms experienced by individuals with lactose intolerance after ingesting dairy products?

    <p>Bloating, pain, gas, and diarrhea</p> Signup and view all the answers

    Why is yogurt better tolerated than milk in lactose intolerant individuals?

    <p>Yogurt contains its own bacterial lactase</p> Signup and view all the answers

    How are hexoses absorbed across the wall of the small intestine?

    <p>By active transport involving Na+</p> Signup and view all the answers

    What is the role of Na+ in the absorption of glucose and galactose in the intestinal lumen?

    <p>Facilitates sugar influx into epithelial cells</p> Signup and view all the answers

    Why is avoiding dairy products challenging for individuals with lactose intolerance?

    <p>Dairy products are a major part of many diets</p> Signup and view all the answers

    What is the simplest treatment for lactose intolerance?

    <p>Avoiding all carbohydrates</p> Signup and view all the answers

    What is the function of micelles in the context of lipid absorption in the gastrointestinal system?

    <p>Serving as carriers to transport lipids to the enterocytes</p> Signup and view all the answers

    How are lipids maintained in contact with the brush border of mucosal cells during absorption?

    <p>Through micelles that collect lipids</p> Signup and view all the answers

    What is the current understanding regarding how lipids enter enterocytes during fat absorption?

    <p>By carriers involvement</p> Signup and view all the answers

    Which components are found in the hydrophobic center of micelles involved in lipid absorption?

    <p>Cholesterol and amphipathic phospholipids</p> Signup and view all the answers

    What role do micelles play in relation to lipid solubilization?

    <p>Facilitating lipid solubilization and transport</p> Signup and view all the answers

    Why are lipids rapidly esterified inside the enterocytes during fat absorption?

    <p>To maintain a favorable concentration gradient from lumen to cells</p> Signup and view all the answers

    Where does the acylation of glycerophosphate and the formation of lipoproteins occur?

    <p>Rough endoplasmic reticulum</p> Signup and view all the answers

    In which part of the small intestine is absorption of long-chain fatty acids greatest?

    <p>Upper parts</p> Signup and view all the answers

    How much of ingested fat is absorbed on a moderate fat intake?

    <p>95%</p> Signup and view all the answers

    Why are infants more susceptible to the ill effects of disease processes that reduce fat absorption?

    <p>Their fat absorption processes are not fully mature</p> Signup and view all the answers

    How is the amount of iron lost from the body regulated in adults?

    <p>Changes in the rate of absorption from the intestine</p> Signup and view all the answers

    How much iron do men lose daily from their body?

    <p>0.6 mg</p> Signup and view all the answers

    What is the mechanism by which protein antibodies in maternal colostrum cross the mammary epithelium and enter the circulation of the infant?

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

    What is the primary method of absorption for intact proteins in adults?

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

    Which of the following foods is NOT mentioned as being allergenic in the text?

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

    What percentage of children is reported to have food allergies according to the text?

    <p>8%</p> Signup and view all the answers

    In individuals with food allergies, what may cause allergic symptoms upon subsequent consumption of the same protein?

    <p>Antigen–antibody reaction</p> Signup and view all the answers

    What role do foreign proteins that enter the circulation play in relation to allergic responses?

    <p>They provoke the formation of antibodies</p> Signup and view all the answers

    Which enzyme is responsible for hydrolyzing the 1- and 3-bonds of triglycerides in fat digestion?

    <p>Pancreatic lipase</p> Signup and view all the answers

    What is the main function of colipase in fat digestion?

    <p>Facilitating the opening of the active site on pancreatic lipase</p> Signup and view all the answers

    Where is lingual lipase secreted in the digestive system?

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

    What do lingual lipase and stomach lipase generate that signals to the gastrointestinal tract?

    <p>Free fatty acids</p> Signup and view all the answers

    Which bonds of triglycerides are hydrolyzed at a low rate by pancreatic lipase?

    <p>2-bonds</p> Signup and view all the answers

    What facilitates pancreatic lipase activity when acting on emulsified fats?

    <p>-COOHterminal domain</p> Signup and view all the answers

    What causes anemia according to the text?

    <p>Iron overload</p> Signup and view all the answers

    In hemochromatosis, what does the pigmentation of the skin indicate?

    <p>Hemosiderin accumulation</p> Signup and view all the answers

    What is the function of the mutated HFE gene in hemochromatosis?

    <p>Inhibits iron absorption</p> Signup and view all the answers

    Which factor plays a role in regulating intestinal absorption of iron?

    <p>State of erythropoiesis in the bone marrow</p> Signup and view all the answers

    What is a consequence of large amounts of hemosiderin accumulation?

    <p>Hepatic carcinoma</p> Signup and view all the answers

    Where is the mutated HFE gene located in those affected by hemochromatosis?

    <p>Short arm of chromosome 6</p> Signup and view all the answers

    Where do amino acids released from peptides get transported out of the enterocytes?

    <p>Along basolateral borders</p> Signup and view all the answers

    What percentage of the digested protein comes from proteins in digestive juices?

    <p>25%</p> Signup and view all the answers

    Where does the majority of the free amino acids get assimilated, leading to little absorption in the ileum?

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

    What is the fate of almost all the protein found in stools according to the text?

    <p>Comes from bacterial action in the colon</p> Signup and view all the answers

    What do studies suggest about the peptidase activities of brush border and mucosal cell cytoplasm when part of the ileum is resected?

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

    What regulation do the enzyme activities related to peptidases in brush border and mucosal cells appear to be subject to?

    <p>Homeostatic regulation</p> Signup and view all the answers

    What is the role of micelles in the absorption of lipids in the gastrointestinal system?

    <p>Facilitating the diffusion of lipids to the brush border of mucosal cells</p> Signup and view all the answers

    How are lipids maintained in solution during the absorption process in the gastrointestinal system?

    <p>By forming micelles with hydrophobic centers</p> Signup and view all the answers

    What is the main function of carriers in the process of lipid absorption in enterocytes?

    <p>Aiding in the transport of lipids into enterocytes</p> Signup and view all the answers

    How do fatty acids and monoglycerides align themselves within the micelles during lipid absorption?

    <p>Hydrophilic heads outside and hydrophobic tails inside</p> Signup and view all the answers

    What happens to lipids once they reach the brush border of mucosal cells in the gastrointestinal system?

    <p>They are absorbed by the cells</p> Signup and view all the answers

    Why are carriers suggested to be involved in lipid absorption into enterocytes?

    <p>To actively transport lipids across the cell membrane</p> Signup and view all the answers

    What is the optimal pH for salivary α-amylase?

    <p>6.7</p> Signup and view all the answers

    Which molecule constitutes around 75% of dietary starch and is branched?

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

    Which disaccharide is also known as milk sugar?

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

    Which type of carbohydrates are digested to any significant degree in the human gastrointestinal tract by human enzymes?

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

    Where does digestion of starch by salivary α-amylase begin?

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

    Which monosaccharide is ingested along with lactose and sucrose?

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

    What is the primary reason that makes yogurt better tolerated than milk in lactose intolerant individuals?

    <p>Yogurt contains its own bacterial lactase.</p> Signup and view all the answers

    How do hexoses like glucose and galactose get transported into the epithelial cells of the small intestine?

    <p>Facilitated by Na+ ions</p> Signup and view all the answers

    Why is the simplest treatment for lactose intolerance mentioned as avoiding dairy products?

    <p>Lactose in dairy products is not sufficiently digested.</p> Signup and view all the answers

    What is the role of commercial lactase preparations in treating symptoms of lactose intolerance?

    <p>They aid in the breakdown of lactose into absorbable sugars.</p> Signup and view all the answers

    Why are hexoses absorbed rapidly across the wall of the small intestine?

    <p>Because hexoses are actively transported</p> Signup and view all the answers

    What causes symptoms like bloating, pain, and diarrhea in individuals with lactose intolerance?

    <p>Unabsorbed osmoles from lactose digestion</p> Signup and view all the answers

    What is the primary location for rapid absorption of amino acids in the gastrointestinal system?

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

    Where does almost all the protein in stools come from according to the text?

    <p>Bacterial action in the colon</p> Signup and view all the answers

    What percentage of digested protein comes from desquamated mucosal cells?

    <p>25%</p> Signup and view all the answers

    Which location experiences little absorption due to assimilation of free amino acids?

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

    What is the fate of only 2–5% of the protein in the small intestine?

    <p>Bacterial digestion in the colon</p> Signup and view all the answers

    How are peptidase activities of brush border and mucosal cell cytoplasm altered during starvation?

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

    What is the main role of hephaestin (Hp) in iron transport?

    <p>Facilitating basolateral transport</p> Signup and view all the answers

    What is the normal plasma iron level in women according to the text?

    <p>110 μg/dL</p> Signup and view all the answers

    Where is most of the iron stored in the body?

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

    What is the composition of apoferritin?

    <p>24 subunits</p> Signup and view all the answers

    What are deposits containing as much as 50% iron called?

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

    What removes Fe2+ from porphyrin and adds it to the intracellular Fe2+ pool?

    <p>HO-2</p> Signup and view all the answers

    What can lead to hemosiderosis according to the text?

    <p>Iron overload</p> Signup and view all the answers

    What genetic disorder is characterized by pigmentation of the skin, pancreatic damage with diabetes, and cirrhosis of the liver?

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

    Where is the mutated HFE gene that commonly leads to hereditary hemochromatosis located?

    <p>Short arm of chromosome 6</p> Signup and view all the answers

    What is one of the characteristics associated with hemochromatosis?

    <p>Gonadal atrophy</p> Signup and view all the answers

    How do individuals who are homogenous for HFE mutations absorb excess iron?

    <p>Due to inhibited expression of duodenal transporters</p> Signup and view all the answers

    Which area is closely linked to the locus where the mutated HFE gene responsible for hemochromatosis is located?

    <p>HLA-A locus</p> Signup and view all the answers

    What is the primary function of the gastrointestinal tract?

    <p>To absorb nutrients and water into the body</p> Signup and view all the answers

    Where do glandular structures deliver secretions in the gastrointestinal tract?

    <p>In the stomach and mouth</p> Signup and view all the answers

    What organs drain secretions into the gastrointestinal tract?

    <p>Pancreas, gallbladder, and salivary glands</p> Signup and view all the answers

    Which part of the gastrointestinal tract is encountered first by a meal or its residues?

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

    Where is the acylation of glycerophosphate and the formation of lipoproteins important in the digestive process?

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

    What is an essential function of secretions from the pancreas and biliary system in digestion?

    <p>To aid in lipid digestion</p> Signup and view all the answers

    Which pancreatic enzyme is released as an inactive precursor and activated by trypsin?

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

    Why does the pancreas secrete a trypsin inhibitor?

    <p>To prevent self-digestion of the pancreas</p> Signup and view all the answers

    What is the role of somatostatin in the gastrointestinal system?

    <p>Inhibits the secretion of GIP and secretin</p> Signup and view all the answers

    What is the primary cause of gastric and duodenal ulceration related to in humans?

    <p>Breakdown of the mucosa barrier</p> Signup and view all the answers

    Where is ghrelin primarily secreted from?

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

    What is the primary function of bile in the gastrointestinal system?

    <p>To aid in the digestion and absorption of fats</p> Signup and view all the answers

    What disrupts the barrier preventing irritation and autodigestion of the mucosa according to the text?

    <p>Aspirin and NSAIDs</p> Signup and view all the answers

    What stimulates the secretion of somatostatin?

    <p>Acid in the gastrointestinal lumen</p> Signup and view all the answers

    What color is bile primarily responsible for?

    <p>Golden yellow</p> Signup and view all the answers

    What is a common cause of ulceration besides infection and overproduction of acid mentioned in the text?

    <p>Zollinger–Ellison syndrome</p> Signup and view all the answers

    What controls the secretion of pancreatic juice primarily?

    <p>Hormonal regulation</p> Signup and view all the answers

    Which cells secrete motilin in the gastrointestinal system?

    <p>Enterochromaffin cells</p> Signup and view all the answers

    How does somatostatin impact the absorption of nutrients in the gastrointestinal system?

    <p>Inhibits glucose absorption</p> Signup and view all the answers

    Which substance is released into the bloodstream along with protons to neutralize gastric acidity?

    <p>Bicarbonate ions</p> Signup and view all the answers

    How is bile similar to pancreatic juice?

    <p>Both contain electrolytes</p> Signup and view all the answers

    What is the function of somatostatin in relation to pancreatic exocrine secretion?

    <p>Inhibits pancreatic exocrine secretion</p> Signup and view all the answers

    What is the effect of NSAIDs on gastric mucosa that can contribute to ulcer development?

    <p>Inhibition of prostaglandin production</p> Signup and view all the answers

    Where are most gastrinomas found in patients with Zollinger–Ellison syndrome?

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

    What is the primary function of the myenteric plexus in the gastrointestinal system?

    <p>Motor control of smooth muscle layers</p> Signup and view all the answers

    Which neurotransmitter is NOT mentioned as part of the gastrointestinal system?

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

    What is the main purpose of digestive secretions in the gastrointestinal system?

    <p>To digest meals into absorbable components</p> Signup and view all the answers

    Which component is NOT part of the sequential action on meal components in the gastrointestinal system?

    <p>Cerebrospinal fluid</p> Signup and view all the answers

    Which area of the body is functionally continuous with the outside environment according to the text?

    <p>Gastrointestinal system</p> Signup and view all the answers

    Which substance's presence is NOT associated with the regulation of intestinal functions in the gastrointestinal system?

    <p>Hyaluronic acid</p> Signup and view all the answers

    Study Notes

    Digestion of Macromolecules

    • Proteins, fats, and complex carbohydrates are primarily digested in the small intestine.
    • Pancreatic juice contains enzymes that break down carbohydrates, proteins, lipids, DNA, and RNA.

    Carbohydrate Digestion

    • Amylase breaks down polysaccharides into oligosaccharides in the small intestine.
    • Oligosaccharidases, such as sucrase, are responsible for further digestion of starch derivatives in the brush border of enterocytes.
    • Sucrase is formed in the small intestine and breaks down sucrose into glucose and fructose.
    • Lactase breaks down lactose into glucose and galactose.
    • α-Amylase is primarily responsible for breaking down starch into oligosaccharides in the small intestine.

    Lipid Digestion

    • Lipase breaks down triglycerides into fatty acids and monoglycerides in the small intestine.
    • Bile salts emulsify lipids, increasing the surface area for enzymatic digestion.
    • Micelles are formed from bile salts and lipids, facilitating lipid absorption.
    • Fatty acids and monoglycerides are transported across the enterocyte membrane via carriers.
    • Lipoproteins are formed in the enterocytes and transported to the lymphatic system.

    Fat Absorption

    • Micelles play a crucial role in lipid solubilization and absorption in the small intestine.
    • Lipids are maintained in contact with the brush border of mucosal cells during absorption.
    • Acylation of glycerophosphate and formation of lipoproteins occur in the enterocytes.

    Iron Absorption

    • Iron is absorbed in the duodenum and proximal jejunum.
    • The amount of iron lost from the body is regulated in adults.
    • Men lose approximately 1 mg of iron daily from their bodies.
    • Hemochromatosis is a genetic disorder characterized by increased iron absorption and storage.

    Protein Digestion

    • Proteins are primarily digested in the small intestine by pancreatic enzymes.
    • Amino acids are absorbed in the small intestine and transported to the liver.
    • The primary location for rapid absorption of amino acids is the proximal small intestine.
    • Almost all protein in stools comes from desquamated mucosal cells.

    Gastrointestinal System

    • The primary function of the gastrointestinal tract is to break down and absorb nutrients.
    • Secretions from the pancreas and biliary system aid in digestion.
    • Glandular structures deliver secretions into the gastrointestinal tract.
    • The small intestine is the primary site for nutrient absorption.

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    Description

    Learn about lactose intolerance and the symptoms individuals experience when ingesting dairy products. Explore therapeutic highlights and treatment options for managing lactose intolerance symptoms.

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