Cholesterol is a major component of atherosclerotic plaque. Cholesterol carried by ______ is linked to coronary heart disease.

Correct Answer: C

Rationale: The correct answer is C: low-density lipoprotein (LDL). LDL is often referred to as "bad cholesterol" because it carries cholesterol from the liver to the cells, leading to the buildup of plaque in the arteries, which can result in coronary heart disease. Micelles are small lipid structures, not carriers of cholesterol. Chylomicrons are large lipoprotein particles that transport dietary fats, not primarily cholesterol. HDL is known as "good cholesterol" as it helps remove cholesterol from the bloodstream back to the liver for excretion, reducing the risk of atherosclerosis.

Correct Answer: C

Rationale: The correct answer is C: Amylase. Amylase is primarily responsible for digesting carbohydrates in the small intestine. It breaks down complex carbohydrates into simpler sugars like maltose and glucose. Pepsin (A) is a stomach enzyme that breaks down proteins, not carbohydrates. Lipase (B) digests fats, not carbohydrates. Trypsin (D) is a pancreatic enzyme that digests proteins, not carbohydrates. Amylase is the only enzyme among the choices that specifically targets carbohydrates for digestion in the small intestine.

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.

Correct Answer: B

Rationale: The correct answer is B: cancer. T suppressor cells play a crucial role in regulating the immune response to prevent excessive activation, which can lead to the development of cancer. In cancer, T suppressor cells may become dysfunctional, allowing cancer cells to evade immune surveillance and proliferate. Autoimmune diseases (choice A) are more associated with a breakdown in immune tolerance, leading to an overactive immune response against self-antigens. Allergies (choice C) involve an exaggerated immune response to harmless substances, primarily driven by IgE antibodies and other immune cells, rather than T suppressor cells. Graft rejection (choice D) is typically mediated by T helper cells and cytotoxic T cells targeting foreign antigens present in transplanted tissues, rather than T suppressor cells.

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.