Which is TRUE?

Correct Answer: D

Rationale: Step-by-step rationale for choice D being correct: 1. ATP is an energy carrier molecule. 2. Adenosine triphosphate (ATP) is a precursor of cyclic AMP. 3. Cyclic AMP is a secondary messenger involved in cellular signaling. 4. Therefore, choice D is true. Summary of incorrect choices: A: Adenosine triphosphate is a high-energy phosphate, not low. B: Reduction involves gain, not loss, of electrons. C: Oxidative phosphorylation occurs in the mitochondria, not the endoplasmic reticulum.

Correct Answer: D

Rationale: The correct answer is D: insulin. Elderly individuals are more likely to develop type 2 diabetes due to a decrease in insulin production by the pancreas and decreased sensitivity to insulin in tissues. Insulin plays a crucial role in regulating blood sugar levels by facilitating the uptake of glucose into cells for energy production. A decline in insulin production or sensitivity can lead to elevated blood sugar levels, contributing to the development of type 2 diabetes. Estrogen (choice A), thyroid hormone (choice B), and follicle-stimulating hormone (choice C) do not directly impact insulin production or sensitivity in the context of type 2 diabetes development in elderly individuals.

Correct Answer: A

Rationale: The correct answer is A: The mouth. Starch digestion begins in the mouth due to the enzyme amylase present in saliva. Amylase breaks down starch into maltose. This process initiates digestion before food reaches the stomach or small intestine. The other choices are incorrect because oesophagus primarily serves as a passage for food, the small intestine is where most digestion and nutrient absorption occur, and the stomach's main role is to break down proteins with the enzyme pepsin, not starch.

Correct Answer: C

Rationale: The correct answer is C: Fats. Fats take the longest to digest due to their complex structure, requiring more time and effort for the stomach to break them down. This slow digestion process leads to fats staying in the stomach longer compared to carbohydrates and proteins. Carbohydrates are typically broken down relatively quickly, while proteins take longer than carbohydrates but are still processed more efficiently than fats. Therefore, fats remain in the stomach longest among the given options.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.