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In an analysis of the amino acid composition of foods, the amino acid occurring in the smallest amount is called:
- A. indispensable.
- B. dispensable.
- C. complementary.
- D. limiting.
Correct Answer: D
Rationale: The correct answer is D, 'limiting.' In the analysis of the amino acid composition of foods, the amino acid that occurs in the smallest amount is referred to as the limiting amino acid. This term is used because when one essential amino acid is deficient, it limits the synthesis of proteins, making it crucial in determining protein quality. Choices A, B, and C are incorrect. 'Indispensable' and 'dispensable' refer to the essentiality of amino acids, and 'complementary' does not describe the concept of the amino acid occurring in the smallest amount.
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Amino acids that can be synthesized by the body in sufficient amounts are known as:
- A. indispensable.
- B. dispensable.
- C. simple.
- D. complex.
Correct Answer: B
Rationale: The correct answer is B, 'dispensable.' Dispensable amino acids are those that the body can synthesize in sufficient amounts, so they are not required to be obtained from the diet. Indispensable amino acids, on the other hand, are essential and must be obtained from the diet because the body cannot produce them in sufficient quantities. Choices C and D, 'simple' and 'complex,' are incorrect as they do not accurately describe amino acids in terms of synthesis by the body.
Pepsinogen secreted by the gastric cells is converted into pepsin by:
- A. enterokinase
- B. hydrochloric acid
- C. gastric lipase
- D. pancreatic lipase
Correct Answer: B
Rationale: Pepsinogen is converted into its active form, pepsin, by hydrochloric acid in the stomach. Hydrochloric acid helps in unfolding the pepsinogen molecule to transform it into pepsin, which is crucial for protein digestion. Therefore, the correct answer is hydrochloric acid (choice B). Enterokinase (choice A) is an enzyme produced in the small intestine that activates trypsinogen into trypsin, not pepsinogen. Gastric lipase (choice C) is an enzyme that digests fats, not involved in converting pepsinogen to pepsin. Pancreatic lipase (choice D) is an enzyme produced by the pancreas that aids in breaking down fats in the small intestine, not part of the process of pepsin activation.
How is the enzyme trypsin activated?
- A. By zymogen.
- B. By bile.
- C. By gastrin.
- D. By enterokinase.
Correct Answer: D
Rationale: The correct answer is D: By enterokinase. Trypsin is activated by enterokinase, an enzyme secreted by the small intestine. Enterokinase plays a crucial role in converting trypsinogen into its active form, trypsin. Choices A, B, and C are incorrect because trypsin is specifically activated by enterokinase, not by zymogen, bile, or gastrin.
What role do the amino acids methionine, tyrosine, and tryptophan play?
- A. Forming neurotransmitters.
- B. Blocking excess protein breakdown.
- C. Increasing production of insulin and thyroxine.
- D. Decreasing energy expenditure.
Correct Answer: A
Rationale: The correct answer is A: Forming neurotransmitters. Methionine, tyrosine, and tryptophan are important amino acids involved in the production of neurotransmitters in the body. Neurotransmitters are chemical messengers that transmit signals across nerve cells, influencing various functions such as mood, memory, and muscle control. Choices B, C, and D are incorrect because these amino acids do not primarily play a role in blocking protein breakdown, increasing insulin and thyroxine production, or decreasing energy expenditure.
What are dextrins?
- A. Polysaccharides.
- B. End products of starch digestion.
- C. Formed in the liver.
- D. Rapidly excreted.
Correct Answer: A
Rationale: Failed to generate a rationale of 500+ characters after 5 retries.