What is the source of maltose during digestion?

Correct Answer: D

Rationale: The correct answer is D: carbohydrates. Maltose is a disaccharide composed of two glucose molecules, which are carbohydrates. During digestion, carbohydrates such as starch are broken down into maltose by enzymes like amylase. Lipids (A), proteins (B), and nucleic acids (C) do not directly contribute to the formation of maltose in the digestive process. Therefore, the source of maltose during digestion is carbohydrates, making option D the correct choice.

Correct Answer: C

Rationale: The correct answer is C because salivary glands secrete an enzyme called amylase that catalyzes the breakdown of carbohydrates into maltose. Amylase specifically targets the bonds between glucose molecules in carbohydrates, resulting in the production of maltose. Therefore, the reaction of carbohydrates + H2O -> maltose is catalyzed by salivary gland secretions. Choice A is incorrect because the breakdown of proteins into peptides is not catalyzed by salivary gland secretions. Choice B is incorrect as peptides are broken down into amino acids, not the other way around. Choice D is incorrect as the breakdown of fats into fatty acids and glycerol is not catalyzed by salivary gland secretions.

Correct Answer: A

Rationale: The correct answer is A because during protein digestion, specific enzymes such as proteases break down proteins into amino acids. Proteins are large molecules made up of amino acids, and the body needs to break them down into individual amino acids for absorption and utilization. Choices B, C, and D are incorrect because hormones do not directly break down proteins, and proteins are not broken down into simple sugars or complex starches during digestion. It is essential to understand the role of enzymes in protein digestion to select the correct answer.

Correct Answer: C

Rationale: Rationale for Correct Answer C: 1. Glycogen is a polysaccharide composed of glucose units. 2. It is synthesized and stored in the liver and muscles. 3. Liver glycogen is used to maintain blood glucose levels. 4. Muscle glycogen is used for energy during physical activity. Summary of Incorrect Choices: A: Red blood cells do not store glycogen; they lack organelles. B: Glycogen is not a protein; it is a carbohydrate. D: Glycogen is not a by-product of sucrose digestion; it is a stored form of glucose.

Correct Answer: C

Rationale: The correct answer is C because absorbed food serves as the raw material for metabolism. Once food is digested and absorbed into the bloodstream, it provides the essential nutrients needed for various metabolic processes in the body, such as energy production, growth, repair, and maintenance of tissues. This is crucial for overall body function and health. Explanation for other choices: A: Absorbed food is not toxic to the body; in fact, it provides essential nutrients. B: Absorbed food stimulating reproduction is not directly related to digestion and absorption. D: Absorbed food does not directly aid in respiration; respiration involves the exchange of gases in the lungs.