Which base is found in RNA but not in DNA? MCQ with Answer and Explanation

Explanation:
The liver uses the urea cycle (ornithine cycle) to convert highly toxic ammonia, produced from amino acid deamination, into less toxic urea, which is excreted by the kidneys. The kidneys filter urea but do not synthesize it. Pancreas is digestive/endocrine, intestine absorbs nutrients.

Explanation:
While the Blood-Brain Barrier (BBB) protects most of the brain, there are specific areas where the BBB is absent or highly permeable. These are the circumventricular organs (CVOs), which are located around the third and fourth ventricles. Because they lack a typical BBB, they can directly sample the chemical composition of the blood and cerebrospinal fluid. This is essential for their functions, which include neuroendocrine regulation (e.g., the area postrema for vomiting, the organum vasculosum of the lamina terminalis for osmoregulation, and the median eminence for hormone release).

Explanation:
Lysosomes are membrane-bound vesicles budded off from the Golgi apparatus. They contain powerful hydrolytic enzymes capable of breaking down proteins, lipids, and nucleic acids. They play a crucial role in autophagy, digesting worn-out cellular organelles. Thus, all three statements are biologically accurate and correct.