Digestion and Absorption of Lipids

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Questions and Answers

What is the primary role of bile salts in lipid digestion?

Produce fatty acids in the mouth

Inhibit the action of lipases

Emulsify large lipid droplets (correct)

Increase the acidity of the stomach

Which enzyme is secreted by the chief cells of the stomach for lipid digestion?

Salivary amylase

Pancreatic lipase

Gastric lipase (correct)

Lingual lipase

What is the end product of lipid digestion in the stomach?

Phospholipids

Diacylglycerides and fatty acids (correct)

Saturated fats

Triglycerides

Which type of fats are suggested to be consumed in moderation?

Saturated fats Signup and view all the answers

What are the products of lipid digestion initiated in the mouth?

Diglycerides, monoglycerides, and fatty acids Signup and view all the answers

Which mechanism facilitates the mechanical digestion of lipids in the small intestine?

Peristalsis Signup and view all the answers

Which type of fats are considered 'good' fats?

Monounsaturated and polyunsaturated fats Signup and view all the answers

What role does lingual lipase play in lipid digestion?

Hydrolyzing triglycerides in the mouth Signup and view all the answers

What condition might be explained by understanding the mechanisms of lipid absorption?

Malabsorption syndromes Signup and view all the answers

What is the main purpose of emulsification during lipid digestion?

To facilitate absorption of fats Signup and view all the answers

What is the primary result of the action of pancreatic lipase and co-lipase on triglycerides?

Hydrolysis to monoacylglycerol and fatty acids Signup and view all the answers

How does cholesterol esterase function in lipid digestion?

Hydrolyzes cholesteryl esters to free cholesterol and fatty acids Signup and view all the answers

What is required for the optimal activity of phospholipase A2?

Bile salts Signup and view all the answers

What component is NOT a primary product of lipid digestion?

Triglycerides Signup and view all the answers

What role do mixed micelles play in the absorption of lipids?

They facilitate transportation of hydrophobic lipids across the unstirred water layer Signup and view all the answers

What component do chylomicrons typically contain after formation in enterocytes?

Triglycerides and vitamins Signup and view all the answers

Which pancreatic enzyme is activated by trypsin?

Phospholipase A2 Signup and view all the answers

What is the function of lysophospholipase in lipid degradation?

To remove a remaining fatty acid from lyso-phospholipid Signup and view all the answers

Which process does NOT take place during lipid digestion?

Synthesis of proteins Signup and view all the answers

What is the result of the hydrolysis of phospholipids by phospholipase A2?

Conversion to lyso-phospholipids Signup and view all the answers

Which of the following types of fats are considered 'good' fats?

Monounsaturated and polyunsaturated Signup and view all the answers

Which of the following statements about lipid digestion in the mouth are correct? (Select all that apply)

Lingual lipase hydrolyzes medium and long-chain triglycerides Signup and view all the answers

Which of the following enzymes are involved in lipid digestion in the stomach?

Gastric lipase Signup and view all the answers

Which of the following statements about gastric lipase is true?

Secreted by the chief cells of the stomach Signup and view all the answers

What do the two enzymes acting on lipids in the stomach do?

They hydrolyse the ester bonds in medium and long chain triglycerides Signup and view all the answers

Which of the following processes are involved in lipid digestion in the small intestine? (Select all that apply)

Further increase surface area of lipid droplets Signup and view all the answers

Which of the following statements about chemical digestion in the small intestine is true?

Pancreatic lipase binds to the surface of the droplet in the presence of pancreatic co-lipase Signup and view all the answers

Which of the following pancreatic enzymes are involved in lipid degradation? (Select all that apply)

Cholesterol esterase Signup and view all the answers

Cholesterol esterase hydrolyzes cholesteryl esters to which of the following?

Cholesterol and free fatty acids Signup and view all the answers

What does Phospholipase A2 digest phospholipid into?

To lyso-phospholipid by removing 1 fatty acid Signup and view all the answers

Which of the following statements about phospholipase A2 are correct? (Select all that apply)

Requires bile salts for optimum activity Signup and view all the answers

What are the functions of lysophospholipase? (Select all that apply)

Removes remaining fatty acid at C1 Signup and view all the answers

Which of the following substances do pancreatic enzymes digest? (Select all that apply)

Triacylglycerol, cholesteryl esters, phospholipids Signup and view all the answers

The products of fat digestion form into which of the following?

Mixed micelles Signup and view all the answers

Which components are included in a mixed micelle? (Select all that apply)

Free fatty acids Signup and view all the answers

Which of the following cells are primarily responsible for the absorption of lipids?

Enterocytes Signup and view all the answers

Which of the following do not require mixed micelles for absorption?

Short-medium chain fatty acids Signup and view all the answers

What is primarily involved in the formation in the enterocyte?

Chylomicron Signup and view all the answers

Fatty acids and monoglycerides are transported into the ........ where they are used to synthesize ......

endoplasmic reticulum, triglyceride Signup and view all the answers

After lipids are synthesized in the endoplasmic reticulum, what is their next step?

Form into chylomicrons and go to the Golgi apparatus Signup and view all the answers

What happens to chylomicrons after they are extruded from the Golgi in enterocytes?

Transported to the basolateral aspect of the enterocyte Signup and view all the answers

Where are chylomicrons dumped after absorption?

Extracellular space and enter the lymph Signup and view all the answers

Study Notes

Learning Outcomes

Understand the digestion process of lipids in the body.
Identify key products generated from lipid digestion.
Explain the absorption mechanism for lipids.
Recognize the significance of malabsorption syndromes.

Sites of Lipid Digestion

Digestion occurs in the mouth, stomach, and small intestine.

Types of Fats

Good Fats: Include monounsaturated and polyunsaturated fats found in vegetable oils (e.g., olive, canola), nuts, seeds, and fish.
Bad Fats: Trans fats are found in processed foods with partially hydrogenated oils.
Saturated Fats: Found in red meat, butter, cheese, and ice cream; should be consumed in moderation.

Lipid Digestion in the Mouth

Mechanical Digestion: Begins with mastication; emulsification breaks down lipid droplets into smaller sizes.
Chemical Digestion: Lingual lipase in saliva hydrolyzes medium and long-chain triglycerides into diglycerides, monoglycerides, and fatty acids.

Lipid Digestion in the Stomach

Two active enzymes:
- Lingual lipase (from the mouth)
- Gastric lipase (secreted by stomach chief cells)
Both enzymes hydrolyze triglycerides, producing diacylglycerides and fatty acids.
Gastric lipase is part of the serine proteases family and is acid-stable.

Lipid Digestion in the Small Intestine

Mechanical Digestion: Continues emulsification, increasing the surface area for enzyme action, aided by peristalsis and bile salts.
Chemical Digestion:
- Pancreatic lipase and co-lipase secreted by the pancreas, bind to lipid droplets.
- These enzymes hydrolyze triglycerides into monoacylglycerol and fatty acids.

Other Pancreatic Enzymes Involved

Cholesterol Esterase: Hydrolyzes cholesteryl esters into cholesterol and free fatty acids, activity enhanced by bile salts.
Phospholipase A2: Digests phospholipids to lyso-phospholipids; activated by trypsin and requires bile salts.
Lysophospholipase: Removes the remaining fatty acid from lyso-phospholipid, yielding a glycerylphosphoryl base.

Lipid Digestion Overview

Pancreatic enzymes digest triacylglycerols, cholesteryl esters, and phospholipids.
Secretion of these enzymes is hormonally regulated.
Primary products of digestion: free fatty acids, free cholesterol, and 2-monoacylglycerol.

Formation of Mixed Micelles

Mixed micelles are composed of bile salts, free fatty acids, free cholesterol, 2-monoacylglycerol, and phospholipids.

Absorption of Lipids by Enterocytes

Hydrophilic surface of micelles aids in transporting hydrophobic lipids across the unstirred water layer to the brush border membrane.
Short and medium-chain fatty acids can directly be absorbed without mixed micelles.

Chylomicron Formation in Enterocytes

Fatty acids and monoglycerides enter the endoplasmic reticulum to synthesize triglycerides.
Triglycerides are combined with cholesterol esters, free cholesterol, phospholipids, vitamins, and apolipoprotein B48 to form chylomicrons.

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Description

This quiz covers the key concepts related to the digestion and absorption of lipids, tailored for the DEM Year 2 course at RCSI. You will explore lipid digestion processes, products of digestion, and the mechanisms involved in absorption. Additionally, the significance of malabsorption will be addressed.

Digestion and Absorption of Lipids - DEM Y2

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