Question

Which of these statements about fat digestion and absorption is false? a. Emulsification by bile salts increases the rate of fat digestion. b. Triglycerides are hydrolyzed by the action of pancreatic lipase. c. Triglycerides are resynthesized from monoglycerides and fatty acids in the intestinal epithelial cells. d. Triglycerides, as particles called chylomicrons, are absotbed into blood capillaries within the villi.

Short answer

The false statement is (d): Triglycerides, as particles called chylomicrons, are absorbed into blood capillaries within the villi. In reality, chylomicrons enter the lymphatic vessels called lacteals within the villi and are transported through the lymphatic system before entering the bloodstream.

Step-by-step solution

Understand each statement

Let's go through each of the four statements to understand the processes they are describing: a. Emulsification by bile salts increases the rate of fat digestion: This statement explains that bile salts aid in breaking down large fat globules into smaller ones (a process called emulsification), which increases the rate at which fats are digested. b. Triglycerides are hydrolyzed by the action of pancreatic lipase: This statement explains that triglycerides (a type of fat) are broken down into their components (glycerol and fatty acids) by an enzyme called pancreatic lipase. c. Triglycerides are resynthesized from monoglycerides and fatty acids in the intestinal epithelial cells: This statement explains that once triglycerides are broken down into monoglycerides and fatty acids, they are reassembled in the intestinal cells to be transported across the intestinal barrier and into the body. d. Triglycerides, as particles called chylomicrons, are absorbed into blood capillaries within the villi: This statement explains that triglycerides are absorbed in the form of particles called chylomicrons, which are taken up by blood capillaries within the finger-like projections (villi) on the surface of the small intestine.

Identify the false statement

Among the four statements, only one is false: a. Emulsification by bile salts increases the rate of fat digestion: This statement is true as bile salts indeed emulsify fats, facilitating their digestion. b. Triglycerides are hydrolyzed by the action of pancreatic lipase: This statement is also true, as pancreatic lipase is the enzyme responsible for breaking down triglycerides. c. Triglycerides are resynthesized from monoglycerides and fatty acids in the intestinal epithelial cells: This statement is true, as the broken-down components of triglycerides are reassembled and transported across the intestinal barrier in the form of triglycerides. d. Triglycerides, as particles called chylomicrons, are absorbed into blood capillaries within the villi: This statement is false. While it is true that triglycerides are assembled into chylomicrons within the intestinal cells, they are not absorbed directly into the blood capillaries. Instead, chylomicrons enter the lymphatic vessels called lacteals within the villi and are transported through the lymphatic system before entering the bloodstream. So, the answer is (d): Triglycerides, as particles called chylomicrons, are absorbed into blood capillaries within the villi is the false statement.

Key concepts

Bile Salts

Bile salts play a crucial role in the digestion of fats. These compounds are made in the liver and stored in the gallbladder until needed. When you consume a meal that contains fat, bile salts are released into the small intestine. Here, they act like "detergents" by emulsifying large fat droplets into much smaller ones. The smaller droplets have a larger surface area that makes it easier for digestive enzymes to break them down.
Bile salts are amphiphilic, which means they have both water-attracting and fat-attracting sides. This unique property helps them stabilize the small fat droplets, preventing them from coming together again. This action significantly increases the efficiency of fat digestion. Without bile salts, fats would not be absorbed efficiently, leading to nutrient deficiencies.

Triglycerides

Triglycerides are the main form of fat found both in your diet and in your body. They are composed of a glycerol molecule attached to three fatty acids. In the context of digestion, triglycerides must be broken down into their individual components, which can be transported across the intestinal wall.
Once ingested, triglycerides come into contact with the pancreatic enzymes in the small intestine. This is necessary because triglycerides are too large and complex to be absorbed intact into the bloodstream. The breaking down of triglycerides is a critical step, allowing them to be turned into monoglycerides and free fatty acids, which are smaller and much more manageable for absorption.

Pancreatic Lipase

Pancreatic lipase is an enzyme that plays an essential role in fat digestion. This enzyme is secreted by the pancreas and activated in the small intestine. One of its primary functions is to break down triglycerides into monoglycerides and free fatty acids. This process is known as hydrolysis.
Hydrolysis is where water molecules are used to break chemical bonds. In the case of triglycerides, the bonds between the glycerol and fatty acids are cleaved, freeing them up for better absorption by intestinal cells. Without pancreatic lipase, fats in your diet would remain in large globules and pass through the digestive tract without being absorbed.

Chylomicrons

Chylomicrons are small particles that encapsulate reassembled triglycerides, phospholipids, cholesterol, and proteins after fat digestion. These particles are formed in intestinal epithelial cells after the digestion and initial absorption steps are complete.
The job of chylomicrons is to transport fats through the lymphatic system before they enter the bloodstream. Unlike other nutrients that go straight into blood capillaries, these are transported via lymph vessels, enabling them to bypass the liver initially. The specialized structure of chylomicrons ensures that lipids, which are not water-soluble, can move easily through the watery environments of the body.

Intestinal Absorption

Intestinal absorption is the final stage of nutrient processing in the digestive system. During this phase, digested nutrients, including fats, are absorbed through the lining of the small intestine. The inner walls of the intestine have tiny hair-like projections called villi and microvilli, which increase the surface area for absorption significantly.
After triglycerides are broken down into monoglycerides and free fatty acids, these molecules diffuse into the cells lining the intestine. They are then reassembled into triglycerides and packaged into chylomicrons for transport. This absorption process is highly efficient, ensuring that a maximum amount of fat from the diet is absorbed and utilized by the body.