Nokea
Which of the following carbohydrates can be transported across the absorptive cells of the intestinal surface?
- A. starch, sucrose, lactose
- B. glycogen, maltose
- C. glucose, fructose, galactose
- D. amylase, maltose, lactose
Correct Answer: C
Rationale: The correct answer is C because glucose, fructose, and galactose are all monosaccharides, which are the simplest form of carbohydrates and can be directly absorbed by the intestinal cells through specific transport proteins. This process occurs through facilitated diffusion or active transport mechanisms. In contrast, choices A and B consist of disaccharides or polysaccharides, which need to be broken down into monosaccharides before absorption can occur. Choice D includes enzymes and disaccharides, which are not directly absorbed but rather involved in the digestion process. Thus, only choice C aligns with the mechanism of carbohydrate absorption in the intestines.
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Which of these processes occurs throughout most of the alimentary canal?
- A. ingestion
- B. propulsion
- C. segmentation
- D. absorption
Correct Answer: B
Rationale: The correct answer is B: propulsion. Propulsion is the process of moving food along the alimentary canal through peristalsis, which is the contraction and relaxation of muscles in the digestive tract. This process occurs throughout most of the alimentary canal, including the esophagus, stomach, small intestine, and large intestine. Ingestion (choice A) occurs at the beginning of the digestive process when food enters the mouth. Segmentation (choice C) is a mixing movement that occurs mainly in the small intestine to aid in digestion. Absorption (choice D) takes place primarily in the small intestine, where nutrients are absorbed into the bloodstream. Therefore, propulsion is the correct answer as it is the continuous movement of food along the digestive tract.
The di- and tripeptides are transported in the enterocytes by peptide transporter 1 that requires:-
- A. Na+
- B. Ca++
- C. H+
- D. Cl-
Correct Answer: C
Rationale: The correct answer is C: H+. Peptide transporter 1 requires a proton gradient for the active transport of di- and tripeptides across the enterocytes. This proton gradient is maintained by the H+ ions. Na+ (Choice A), Ca++ (Choice B), and Cl- (Choice D) are not directly involved in the transport of di- and tripeptides by peptide transporter 1. Na+ is primarily involved in glucose and amino acid transport, Ca++ in bone formation and muscle contraction, and Cl- in maintaining osmotic balance. Therefore, the correct answer is H+ as it is crucial for the functioning of peptide transporter 1.
The pacemaker signal generated by the SA node spreads to the ventricles by passing through the AV node. What would happen to the contraction of the ventricles if there was a complete block at the AV node?
- A. the ventricles would cease beating
- B. the ventricles would beat very fast and uncontrollably
- C. the ventricles would contract rhythmically, but more slowly
- D. the ventricles would contract at the same rate as the atria
Correct Answer: C
Rationale: Rationale: A complete block at the AV node would prevent the transmission of the pacemaker signal from the SA node to the ventricles. As a result, the ventricles would not receive the signal to contract at their normal rate. Instead, they would rely on their inherent ability to generate impulses, resulting in a slower, but still rhythmic contraction. This scenario is known as an escape rhythm, where a lower pacemaker takes over in the absence of the SA node signal.
Summary:
A: the ventricles would cease beating - Incorrect, as the ventricles have their own intrinsic pacemaker.
B: the ventricles would beat very fast and uncontrollably - Incorrect, as a complete AV block would lead to a slower rhythm.
D: the ventricles would contract at the same rate as the atria - Incorrect, as the ventricles and atria have different intrinsic rates.
Which of the following mechanisms most accurately describes how pseudo-membranous colitis caused by Clostridium difficile is produced?
- A. elaboration of an enterotoxin following colonization of the colon
- B. ingestion of a preformed toxin
- C. invasion and destruction of mucosa by the organism
- D. host immune response to the organism
Correct Answer: A
Rationale: The correct answer is A because Clostridium difficile produces toxins, specifically enterotoxins, which cause damage to the intestinal mucosa leading to pseudo-membranous colitis. The organism colonizes the colon and then elaborates the toxins, which disrupt the mucosal barrier.
Choice B is incorrect as there is no preformed toxin ingested; the toxin is produced by the organism after colonization. Choice C is incorrect as Clostridium difficile does not invade and destroy the mucosa directly. Choice D is incorrect as the host immune response is a consequence of the toxin production, not the primary mechanism of disease.
Which of these structures is responsible for the production of bile?
- A. pancreas
- B. liver
- C. gallbladder
- D. small intestine
Correct Answer: B
Rationale: The correct answer is B: liver. The liver is responsible for the production of bile, which is a greenish-yellow fluid that aids in digestion by emulsifying fats. Bile is stored and concentrated in the gallbladder (not produced by it). The pancreas produces digestive enzymes, not bile. The small intestine is where bile is released to help with the digestion of fats, but it is not responsible for its production. Therefore, the liver is the correct answer as it is the primary organ involved in bile production.