Which structure produces a substance that aids in the mechanical breakdown of fats?

Answer Explanation

C) small intestine

- Correct: Chemical digestion in humans is a complex process involving various enzymes acting on different nutrients. While digestion does begin in the mouth with the action of enzymes like salivary amylase on carbohydrates, the majority of chemical digestion occurs in the small intestine. Enzymes secreted by the pancreas (such as pancreatic amylase, lipase, and proteases) and the small intestine itself (such as maltase, sucrase, lactase, and peptidases) break down carbohydrates, fats, and proteins into smaller molecules. Additionally, bile salts produced by the liver and stored in the gallbladder aid in the emulsification and digestion of fats in the small intestine. Therefore, chemical digestion largely concludes in the small intestine before nutrients are absorbed into the bloodstream.

A) esophagus

- Incorrect: The esophagus is primarily involved in the mechanical process of swallowing, which pushes food down into the stomach. While some minor enzymatic activity may occur due to saliva coating the food during swallowing, significant chemical digestion does not occur in the esophagus.

B) stomach

- Incorrect: While the stomach does play a role in chemical digestion, particularly in the breakdown of proteins by the enzyme pepsin and the denaturation of proteins by hydrochloric acid, the majority of chemical digestion occurs in the small intestine. The stomach mainly serves to mechanically churn food and begin the process of protein digestion.

D) gallbladder

- Incorrect: The gallbladder stores and releases bile produced by the liver, which aids in the emulsification and digestion of fats in the small intestine. However, the gallbladder itself is not directly involved in chemical digestion, and the majority of digestive enzymes are not secreted or stored in the gallbladder.

Answer Explanation

A) Mouth, Esophagus, Stomach: This option is incorrect because while saliva in the mouth does contain digestive enzymes (such as amylase for breaking down carbohydrates), the esophagus is not a site of enzyme secretion. The stomach secretes gastric juices which primarily contain hydrochloric acid and pepsinogen (which is converted to pepsin, a protein-digesting enzyme), but the esophagus itself does not secrete digestive enzymes.

B) Stomach, Small Intestine, Large Intestine: This option is incorrect because while both the small intestine and the large intestine play crucial roles in digestion and absorption, enzyme secretion mainly occurs in the stomach and small intestine. The large intestine primarily absorbs water and salts and does not secrete digestive enzymes.

C) Mouth, Stomach, Small Intestine: This option is correct. Enzymes are secreted in the mouth (amylase), stomach (pepsin for protein digestion), and small intestine (various enzymes including pancreatic enzymes like lipase, protease, and amylase, as well as enzymes produced by the intestinal lining).

D) Esophagus, Stomach, Large Intestine: This option is incorrect because while the stomach does secrete digestive enzymes, the esophagus and large intestine do not. The large intestine primarily absorbs water and salts and does not secrete digestive enzymes.

Answer Explanation

D) a lack of essential amino acids in the diet

- Correct: Kwashiorkor is a form of severe acute malnutrition that occurs due to inadequate protein intake, particularly deficient in essential amino acids. When a child's diet is changed from high-protein breast milk to watery cereal, which is often low in protein and deficient in essential amino acids, the child may develop kwashiorkor despite receiving calories. Essential amino acids are necessary for proper growth, immune function, and overall health. Without an adequate supply of essential amino acids, the body cannot synthesize proteins required for various physiological processes, leading to symptoms such as stunted growth, lethargy, edema (swelling), and weakened immune function, which are characteristic of kwashiorkor.

A) too many nucleic acids in the diet

- Incorrect: Kwashiorkor is not caused by an excess of nucleic acids in the diet. Nucleic acids are the building blocks of DNA and RNA and are not directly related to the development of kwashiorkor.

B) an overconsumption of complete protein foods

- Incorrect: Kwashiorkor results from a deficiency in protein intake, particularly inadequate consumption of essential amino acids, rather than an overconsumption of complete protein foods.

C) not enough carbohydrates in the diet

- Incorrect: While a diet lacking in carbohydrates can lead to energy deficiency, it does not directly cause the symptoms of kwashiorkor. Kwashiorkor is primarily associated with inadequate protein intake, not insufficient carbohydrate intake.