Nokea
At what pH does the digestion of protein by pepsin in the stomach require?
- A. 1.8 and 3.5.
- B. 4.8 and 7.0.
- C. 6.8 and 8.5.
- D. 7.8 and 10.0.
Correct Answer: A
Rationale: The correct answer is A: 1.8 and 3.5. Pepsin, an enzyme involved in protein digestion, functions optimally in an acidic environment, specifically between pH 1.8 and 3.5. This low pH is necessary for pepsin to break down proteins effectively. Choices B, C, and D are incorrect because pepsin requires a highly acidic environment, ruling out the pH ranges listed in those options.
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The interrelated network of nerves within the gastrointestinal wall that regulates its muscular action is known as the:
- A. gastric nerve plexus.
- B. biliary nerve plexus.
- C. intramural nerve plexus.
- D. intestinal nerve plexus.
Correct Answer: C
Rationale: The correct answer is C - intramural nerve plexus. This network of nerves regulates the muscular movements within the gastrointestinal wall. The gastric nerve plexus (choice A) specifically relates to the stomach, not the entire gastrointestinal tract. The biliary nerve plexus (choice B) is associated with the bile ducts and gallbladder, not the regulation of muscular action. The intestinal nerve plexus (choice D) is a general term that doesn't specifically refer to the network of nerves within the gastrointestinal wall.
Ketones are produced when:
- A. carbohydrate stores are depleted.
- B. excess protein is consumed.
- C. protein stores are depleted.
- D. fat stores are depleted.
Correct Answer: A
Rationale: Ketones are produced when the body uses fat for energy due to the depletion of carbohydrate stores. When carbohydrate stores are depleted, the body turns to fat as its primary source of energy, leading to the production of ketones. Excess protein consumption does not directly lead to ketone production. Similarly, the depletion of protein stores or fat stores is not directly related to the production of ketones.
The lining of the stomach and intestine is protected from self-digestion by:
- A. pepsinogen.
- B. bile.
- C. mucus.
- D. fat.
Correct Answer: C
Rationale: The correct answer is C: mucus. Mucus forms a protective barrier that prevents the stomach and intestine from digesting themselves. Pepsinogen (choice A) is an inactive form of pepsin, a digestive enzyme, and does not protect the stomach lining. Bile (choice B) aids in the digestion and absorption of fats but does not protect the stomach lining. Fat (choice D) is a nutrient and energy source; it does not play a role in protecting the stomach and intestine from self-digestion.
What are the small, fingerlike projections into the intestinal lumen called?
- A. Villi
- B. Goblets
- C. Lacteals
- D. Polyps
Correct Answer: A
Rationale: The correct answer is A: Villi. Villi are small fingerlike projections in the intestine that increase the surface area for nutrient absorption. Goblets (choice B) are mucus-secreting cells in the intestines. Lacteals (choice C) are lymphatic vessels in the small intestine that absorb dietary fats. Polyps (choice D) are abnormal tissue growths.
What is the chemical structure that forms the base component of an amino acid?
- A. carboxyl group
- B. carbon chain
- C. radicals
- D. amino group
Correct Answer: D
Rationale: The correct answer is the amino group. Amino acids consist of an amino group (NH2), a carboxyl group (COOH), a hydrogen atom, and a variable side chain attached to a central carbon atom. The amino group is essential for the formation of proteins. The carboxyl group is not the base component but another important functional group in amino acids. Carbon chain and radicals are not specific chemical structures that form the base component of an amino acid.