3.3.3 Absorption

What is required for the co-transport of amino acids into epithelial cells in the ileum?

• Potassium ions

• Sodium ions

• Calcium ions

• Chloride ions

Answer explanation

Sodium ions are essential for the co-transport of amino acids into epithelial cells in the ileum. They create a gradient that facilitates the uptake of amino acids via sodium-dependent transporters.

How do amino acids move across the epithelial cell into the capillaries?

• Active transport

• Simple diffusion

• Facilitated diffusion

• Osmosis

Answer explanation

Amino acids move across epithelial cells into capillaries primarily through facilitated diffusion, which utilizes specific transport proteins to help them cross the cell membrane without expending energy.

What maintains the concentration gradient of sodium ions in the epithelial cells?

• Sodium-glucose pump

• Sodium-potassium pump

• Calcium pump

• Proton pump

Answer explanation

The sodium-potassium pump actively transports sodium ions out of epithelial cells and potassium ions in, maintaining the concentration gradient essential for various cellular functions.

Which molecules are co-transported with sodium ions into epithelial cells in the small intestine?

• Amino acids

• Glucose

• Fatty acids

• Glycerol

Answer explanation

In the small intestine, glucose and amino acids are co-transported with sodium ions into epithelial cells via sodium-glucose transporters. This process utilizes the sodium gradient to facilitate glucose and amino acid absorption.

What are the products of lipid digestion?

• Amino acids and peptides

• Monosaccharides and disaccharides

• Fatty acids, monoglycerides, and glycerol

• Nucleotides and nucleosides

Answer explanation

Lipid digestion primarily produces fatty acids, monoglycerides, and glycerol. These components are the end products of breaking down fats, unlike the other options which pertain to proteins, carbohydrates, and nucleic acids.

What is the role of micelles in lipid absorption?

• They transport glucose molecules

• They aid the transport of monoglycerides and fatty acids to the epithelial cells

• They break down proteins into amino acids

• They facilitate the absorption of vitamins

Answer explanation

Micelles are essential in lipid absorption as they encapsulate monoglycerides and fatty acids, facilitating their transport to the epithelial cells of the intestine for absorption into the bloodstream.

How do monoglycerides and fatty acids enter the epithelial cells?

• Active transport

• Facilitated diffusion

• Simple diffusion

• Endocytosis

Answer explanation

Monoglycerides and fatty acids enter epithelial cells primarily through simple diffusion. Their small size and hydrophobic nature allow them to pass freely through the lipid bilayer of the cell membrane.

What happens to longer fatty acid chains within the epithelial cells?

• They are directly absorbed into the blood

• They recombine with monoglycerides and glycerol to form triglycerides

• They are broken down into smaller molecules

• They are stored as energy reserves

Answer explanation

Longer fatty acid chains are not directly absorbed into the blood. Instead, they recombine with monoglycerides and glycerol in epithelial cells to form triglycerides, which are then transported in lipoproteins.

What structure do triglycerides form to be transported in the body?

• Micelles

• Chylomicrons

• Liposomes

• Vesicles

Answer explanation

Triglycerides are transported in the body as chylomicrons, which are lipoprotein particles that carry dietary lipids from the intestines to other locations in the body. Micelles, liposomes, and vesicles serve different functions.

Where are chylomicrons transported after being formed in the epithelial cells?

• Directly into the bloodstream

• Into the lymphatic system via lacteals

• Into the liver for processing

• Into the stomach for further digestion

Answer explanation

Chylomicrons are large lipoproteins formed in the intestinal epithelial cells and are transported into the lymphatic system via lacteals, not directly into the bloodstream or other options.