In the tunica mucosa and submucosa of the small intestine, a series of folds called the ______ functions to ______.

Correct Answer: A

Rationale: The correct answer is A: plicae circulares; increase surface area. Plicae circulares are circular folds in the small intestine that increase surface area for nutrient absorption. They help in maximizing contact with digested food. Villi and microvilli are structures on the surface of the small intestine that further increase surface area for absorption but are not the folds themselves. Rugae are folds found in the stomach, not the small intestine.

Correct Answer: A

Rationale: The correct answer is A: chylomicron. After absorption, free fatty acids and glycerol are recombined in the epithelial cell to form triglycerides. These triglycerides are then packaged with proteins to form chylomicrons, which are lipoprotein particles that transport dietary fats through the lymphatic system and bloodstream. Chylomicrons are essential for the absorption of dietary fats and fat-soluble vitamins. Summary: - B: Micelle is incorrect because micelles are formed in the lumen of the small intestine to aid in the absorption of lipids but do not involve recombination of fatty acids and glycerol. - C: Lipoprotein is incorrect because while chylomicrons are a type of lipoprotein, the specific process described in the question is not about general lipoprotein formation. - D: Fatty droplet is incorrect as it does not involve the recombination and protein coating process described in the question.

Correct Answer: B

Rationale: The correct answer is B because the colonic microbiota performs multiple essential functions such as aiding in digestion, producing vitamins, regulating immune function, and maintaining gut barrier integrity. Option A is incorrect as it focuses on dietary fiber intake rather than the microbiota's functions. Option C is incorrect because while acetate, propionate, and butyrate are important organic acids produced, they are not the only ones. Option D is incorrect as the microbiota's establishment of an 'acetate buffer' does not necessarily suppress the growth of all pathogenic bacteria.

Correct Answer: D

Rationale: The correct answer is D because the hypothalamus acts as the body's thermostat and controls temperature regulation. When the body detects an infection or other triggers, the hypothalamus resets the temperature set point higher, causing a fever response to help fight off the infection. Choices A, B, and C are incorrect because while an infection can trigger a fever response, it is the hypothalamus that ultimately controls and initiates the response by resetting the temperature set point, not a local widening of blood vessels or activation of the complement system.

Correct Answer: B

Rationale: The correct answer is B: Resveratrol can mimic the effects of caloric restriction in worms, yeast, and flies. This is true because resveratrol, a compound found in red wine, has been shown to activate certain proteins and enzymes that are also activated during caloric restriction, leading to improved health and longevity in these organisms. A is incorrect because caloric restriction typically leads to decreased insulin signaling, not stimulation. C is incorrect because while CR has been shown to increase lifespan in various animal models, there is limited evidence to support its effects on human lifespan. D is incorrect because not all statements are true - only B is supported by scientific evidence.