GI absorption and digestion

Which of the following macromolecules is digested in the small intestine?

• Proteins

• Carbohydrates

• Lipids

• Nucleic acids

• All of the above

Answer explanation

All macromolecules - proteins, carbohydrates, lipids, and nucleic acids - are digested in the small intestine.

Which of the following is true about types of digestion?

• Luminal digestion is carried out by the enzymes secreted by enterocytes.

• Luminal digestion is carried out by the enzymes secreted by salivary glands only.

• Membrane digestion is carried out by the enzymes secreted by salivary glands, stomach, and pancreas.

• Membrane digestion is carried out by the enzymes secreted by enterocytes.

• None of the above

Answer explanation

1.Luminal or cavity digestion takes place in the lumen of the GI tract and is carried out by the enzymes secreted by salivary glands, stomach and pancreas.

2.Membrane or contact digestion is carried out by hydrolytic enzymes synthesized by the enterocytes and inserted in their brush border as integral parts of the microvillar membrane.

Which of the following chemical characteristics of digestive enzymes is not true?

• Protein

• Water soluble

• Optimum pH

• broad range substrates to digest

• Be inactivated by the inappropriate pH

Answer explanation

The chemical characteristics of the digestive enzymes is protein and water soluble. Each enzyme has the optimum pH and is specific for its substrate to digest. Also, it can be inactivated by the inappropriate pH.

Which of the following is the same basic process for the chemical digestion of all ingested food?

• Catalysis

• Hydrolysis

• Genesis

• Synthesis

• None of the above

Answer explanation

•The chemistry of digestion of all food stuffs id the same basic process of hydrolysis which required the different GI enzymes to promote the reaction for each type of food.

Where does the majority of nutrient absorption take place in the human digestive system?

• Stomach

• Large intestine

• Esophagus

• Small intestine

• Colon

Answer explanation

The majority of nutrient absorption takes place in the small intestine, where nutrients from food are absorbed into the bloodstream for distribution throughout the body.

Which of the following is true about the characteristics of tight junction and fluid absorption?

• Tight epithelia promotes absorption of isotonic absorbate.

• Tight epithelia promotes absorption of hypotonic absorbate.

• Leaky epithelia promotes absorption of isotonic absorbate.

• Leaky epithelia promotes absorption of hypertonic absorbate.

• None of above

Answer explanation

Tight epithelia promote absorption of hypertonic absorbate while leaky epithelia promote absorption of isotonic absorbate.

Which following is not true about the enzymes responsible for breaking down carbohydrate in the small intestine?

• Salivary α-amylase

• Pancreatic α-amylase

• Isomaltase (α-dextrinase)

• Maltase (Glucoamylase)

• Sucrase

Answer explanation

Salivary α-amylases is inactivated at pH below 5.0 after mixing with the gastric acids in stomach. The enzymes responsible for breaking down carbohydrate in the small intestine are pancreatic α-amylases, lactase, sucrase, α-dextrinase (isomaltase) and glucoamylase (maltase) in the small intestine.

Which following is not true about the absorption of carbohydrate in the small intestine?

• Glucose and galactose are uptaken by sodium-glucose cotransporter 1 (SGLT1) at luminal membrane of enterocytes.

• Fructose is uptake by glucose transporter 5 (GLUT5) at luminal membrane of enterocytes.

• Glucose, galactose and fructose are transported to blood stream via glucose transporter 2 (GLUT2).

• Glucose and galactose are uptaken by secondary active transport.

• Glucose transporter 5 helps facilitate diffusion of glucose.

What is the cause of lactose intolerance?

• Lactate deficiency

• Colonic bacteria

• Lack of water intake

• Peptic ulcer

• Chronic irritation of intestinal mucosae

Where does protein digestion begin in the human digestive system?

• Stomach

• Small intestine

• Esophagus

• Mouth

• Colon

Answer explanation

Protein digestion begins in the mouth in the human digestive system where enzymes like amylase start breaking down proteins into smaller peptides.