Lipid Digestion & Absorption Quiz
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Questions and Answers

What configuration is described when the two hydrogen atoms stick out on the same side of the chain in a fatty acid?

  • Cis configuration (correct)
  • Saturated configuration
  • Trans configuration
  • Partially hydrogenated configuration

    • How does the number of double bonds in a fatty acid affect its flexibility when in a cis configuration?

  • More double bonds increase flexibility
  • Double bonds do not affect flexibility
  • Flexibility is only determined by carbon chain length
  • More double bonds decrease flexibility (correct)

    • Which of the following fatty acids contains three double bonds based on the provided structure?

  • Linoleate (correct)
  • Stearic acid
  • Oleic acid
  • Arachidonic acid

    • Which statement is true about fatty acids with a cis configuration?

    <p>They are less stable than trans fatty acids</p> Signup and view all the answers

    Which of these compounds is characterized by having an 18-carbon chain and three double bonds at specified positions?

    <p>Alpha-linolenic acid</p> Signup and view all the answers

    What makes up 95% of nutritional lipids?

    <p>Fats and oils</p> Signup and view all the answers

    Which of the following statements about triglycerides is true?

    <p>Triglycerides are the primary form of dietary fats.</p> Signup and view all the answers

    What is the ideal substrate for lingual lipase?

    <p>Short chain triglycerides</p> Signup and view all the answers

    Which of the following is a major dietary source of lipids from animal sources?

    <p>Fish and poultry</p> Signup and view all the answers

    Which type of lipid accounts for less than 10% of dietary lipids?

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

    What pH range is lingual lipase active in?

    <p>2.0 - 7.5</p> Signup and view all the answers

    How much lipid do we typically ingest daily?

    <p>100g</p> Signup and view all the answers

    Which of the following is primarily a plant source of lipids?

    <p>Cooking oils</p> Signup and view all the answers

    What is the primary function of mixed micelles in lipid absorption?

    <p>Solubilize ingested lipids for efficient absorption</p> Signup and view all the answers

    Which enzyme found in blood capillaries facilitates the hydrolysis of triglycerides?

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

    What must happen to dietary triglycerides before absorption can occur?

    <p>They must be hydrolyzed into fatty acids and glycerol</p> Signup and view all the answers

    What is steatorrhea commonly associated with?

    <p>Increased lipid losses in feces</p> Signup and view all the answers

    What can cause lipid malabsorption?

    <p>Liver disease leading to bile salt deficiency</p> Signup and view all the answers

    How much lipid loss in feces is typically observed in lipid malabsorption?

    <p>30g/day</p> Signup and view all the answers

    What is the role of chylomicrons in lipid transport?

    <p>Transport lipids from the enterocytes to the bloodstream</p> Signup and view all the answers

    Fatty acids need to be partitioned into which phase for absorption?

    <p>Micellar phase</p> Signup and view all the answers

    What is the primary function of gastric lipase in lipid digestion?

    <p>It is primarily effective for short to medium chain fatty acids.</p> Signup and view all the answers

    Which substances stimulate the secretion of pancreatic juices?

    <p>Presence of lipids and partially digested proteins.</p> Signup and view all the answers

    What role do bile salts play in fat digestion?

    <p>They act as effective emulsifying agents for fats.</p> Signup and view all the answers

    How does cholecystokinin (CCK) affect gastric motility?

    <p>It decreases gastric motility, slowing the release of contents.</p> Signup and view all the answers

    What triggers the release of secretin in the intestine?

    <p>Low pH of the chyme entering the intestine.</p> Signup and view all the answers

    Which digestive enzyme is primarily responsible for fat digestion in the small intestine?

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

    In which group of individuals is gastric and lingual lipase crucial for digestion?

    <p>Neonates whose primary calorie source is milk fat.</p> Signup and view all the answers

    What is the effect of bicarbonate released by the pancreas?

    <p>It neutralizes the pH of the intestinal contents.</p> Signup and view all the answers

    What is the primary enzyme that hydrolyzes cholesteryl esters?

    <p>Pancreatic cholesteryl ester hydrolase</p> Signup and view all the answers

    Which product is NOT formed during the degradation of phospholipids?

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

    What products result from lipid digestion in the jejunum?

    <p>Free fatty acids, free cholesterol, and 2-monoacylglycerol</p> Signup and view all the answers

    What percentage of bile salts is typically lost in feces after reabsorption?

    <p>5%</p> Signup and view all the answers

    Where does the resynthesis of triacylglycerols and cholesteryl esters primarily occur?

    <p>Endoplasmic reticulum of enterocytes</p> Signup and view all the answers

    What is primarily absorbed by the enterocytes following lipid digestion?

    <p>Fatty acids and 2-monoacylglycerol</p> Signup and view all the answers

    Which enzyme acts on lysophospholipid to form glycerylphospholipid base?

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

    What role do bile salts play in cholesteryl ester degradation?

    <p>They increase the activity of pancreatic cholesteryl ester hydrolase.</p> Signup and view all the answers

    Study Notes

    Lipid Digestion & Absorption

    • Mixed Micelles transport poorly water-soluble lipids like cholesterol and fat-soluble vitamins (A, D, E, K).
    • Bile Salts are essential for efficient lipid absorption, solubilizing ingested lipids.
    • Chylomicrons are formed in enterocytes and transport fats via lymphatic capillaries into the bloodstream.
    • Lipoprotein Lipase, found on blood capillary walls, hydrolyzes triglycerides in chylomicrons into fatty acids and glycerol for energy or storage.

    Triglyceride Assimilation

    • Dietary Triglycerides must be hydrolyzed into fatty acids, monoglycerides, and glycerol before absorption.
    • Micelles form to promote absorption of fatty acids into the intestinal wall.
    • Chylomicrons are formed from the resynthesis of triglycerides from absorbed glycerol and fatty acids.

    Malabsorption

    • Lipid Malabsorption leads to elevated lipid excretion in feces due to impaired digestion or absorption.
    • Conditions like cystic fibrosis (CF) and short bowel syndrome can cause lipid malabsorption.
    • Steatorrhea refers to significant fat losses (around 30g/day) in stool, including fat-soluble vitamins and essential fats.
    • Bile Salt Deficiency caused by liver disease or bile duct obstruction contribute to steatorrhea.

    Sources of Fats for Metabolism

    • Dietary Fats are the primary source.
    • Stored Fat in adipose tissue is another source.
    • Synthesized Fat from excess carbohydrates is a third source.

    Dietary Composition of Lipids

    • We consume approximately 100g of lipids daily.
    • Triglycerides make up over 90% of our lipid intake.
    • Other lipids: cholesterol, cholesteryl esters, phospholipids, and free fatty acids.

    Dietary Sources

    • Animal Sources: Dairy products (milk, cheese, butter), meat, eggs, fish, poultry.
    • Plant Sources: Cooking oils, nuts, seeds, avocados.

    Digestion in Mouth

    • Lingual Lipase is secreted by the tongue.
    • Works optimally at low pH (2.0-7.5).
    • Primarily breaks down short-chain triglycerides (e.g., milk fat).

    Digestion in Stomach

    • Gastric Lipase is secreted in small quantities.
    • Less effective on long-chain fatty acids; mainly works on short to medium chain fatty acids.
    • Plays a significant role in lipid digestion for infants and those with pancreatic insufficiency.

    Digestion in Small Intestine

    • Main Site for fat digestion due to pancreatic lipase and bile salts.
    • Bile Salts are emulsifiers for fats, increasing their surface area for pancreatic lipase action.
    • Pancreatic Juices are secreted upon stimulation by:
      • Acidic gastric content entering the duodenum
      • Secretin and cholecystokinin (CCK) hormones.

    Control of Digestion

    • Cholecystokinin (CCK) is released by the duodenum in response to lipids and proteins, stimulating gallbladder bile release, decreasing gastric motility, and promoting satiety.
    • Secretin is released in response to low pH of chyme, stimulating pancreatic bicarbonate secretion for neutralization.
    • Bile Salts are reabsorbed after aiding lipid absorption.

    Cholesteryl Ester Degradation

    • Dietary cholesterol is mainly in the free form, with a small portion as cholesteryl esters.
    • Pancreatic Cholesteryl Ester Hydrolase (Cholesterol Esterase) hydrolyzes cholesteryl esters to cholesterol and free fatty acids.
    • Bile Salts enhance the activity of this enzyme.
    • Phospholipase A2 removes one fatty acid from phospholipids, forming lysophospholipids.
    • Lysophospholipase further breaks down lysophospholipids.

    Lipid Absorption

    • Free Fatty Acids, Cholesterol, 2-monoacylglycerol: Products of lipid digestion in the jejunum.
    • Mixed Micelles deliver these products to the enterocyte brush border membrane.
    • Enterocytes absorb the lipids.
    • Bile Salts are largely reabsorbed back into circulation with only a small amount lost in feces.

    Resynthesis

    • Absorbed lipids are transported to the endoplasmic reticulum of enterocytes.
    • Triglycerides and cholesteryl esters are re-synthesized in the enterocytes.

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    Related Documents

    Lipid Metabolism Lecture Notes PDF

    Description

    Test your knowledge on the complex processes of lipid digestion and absorption. This quiz covers mixed micelles, bile salts, chylomicrons, and the role of lipoprotein lipase. Understand the implications of lipid malabsorption and how dietary triglycerides are assimilated.

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