Answer: C. 10

Explanation: There are 10 essential amino acids that must be obtained from the diet because the human body cannot synthesize them. These amino acids are vital for protein synthesis and overall metabolic function.

Answer: D. 8

Explanation: Carotenoids are biosynthesized from eight isoprene units. This assembly creates long, conjugated chains that contribute to their vibrant colors and antioxidant properties in plants and other organisms.

Answer: B. Lysozyme

Explanation: Bacteriophages often carry lysozyme, an enzyme that degrades the bacterial cell wall to facilitate the release of viral progeny. Its presence is critical for the lytic cycle in phage replication.

Answer: B. Biotin

Explanation: While FAD, NAD+, lipoic acid, and vitamin C are coenzymes involved in redox reactions, biotin functions as a coenzyme in carboxylation reactions rather than electron transfer, making it the exception.

Answer: D. Apoptosis

Explanation: The p53 protein is a tumor suppressor that normally promotes apoptosis in response to DNA damage. By triggering programmed cell death, p53 prevents the propagation of mutated cells and helps maintain genomic stability.

Answer: B. 29

Explanation: Glucagon is composed of 29 amino acids. This linear peptide hormone is crucial for blood glucose regulation by promoting glycogenolysis and gluconeogenesis in the liver.

Answer: C. Cytomegalovirus

Explanation: Cytomegalovirus does not use reverse transcriptase, unlike retroviruses such as HIV and HTLV, or partially double-stranded DNA viruses like hepatitis B, which require reverse transcription during replication.

Answer: C. Cytoplasm

Explanation: Glycolysis is a metabolic pathway that occurs in the cytoplasm. It is the initial step in cellular respiration, breaking down glucose into pyruvate and generating a small amount of ATP.

Answer: A. Complement proteins

Explanation: Complement proteins are integral to the immune system; they participate in processes such as opsonization, cell lysis, and inflammation, enhancing the ability of antibodies to clear pathogens.

Answer: D. 6

Explanation: Triterpenes are constructed from six isoprene units, which combine to form complex molecules with diverse biological functions. This assembly is central to the structure of many naturally occurring terpenoids.

Answer: A. Bacillus

Explanation: Bacillus is a genus of bacteria known for its ability to form endospores, which help the organism survive harsh environmental conditions through dormancy and resistance.

Answer: B. 1,3,7

Explanation: In a purine ring, the nitrogen atoms are located at positions 1, 3, and 7. This precise arrangement is critical for the structure and base-pairing properties of purines in nucleic acids.

Answer: C. C25H40

Explanation: A compound assembled from five isoprene units typically has the formula C25H40. This reflects the standard biosynthetic pathway in terpenoid formation with the correct number of carbon atoms.

Answer: D. a base + a sugar + phosphate

Explanation: A nucleotide is composed of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. This tripartite structure forms the building blocks of nucleic acids.

Answer: A. Cytosol

Explanation: Most phase II drug-metabolizing enzymes, apart from those involved in glucuronidation, are located in the cytosol. Their cytosolic localization facilitates conjugation reactions that increase drug solubility.

Answer: A. Sialic acid

Explanation: Oseltamivir and Zanamivir mimic the structure of sialic acid, which allows them to competitively inhibit the influenza virus neuraminidase enzyme, thereby preventing viral release and spread.

Answer: D. Geranyl pyrophosphate

Explanation: Isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) condense to form geranyl pyrophosphate, a key precursor molecule in the biosynthesis of terpenes and terpenoids.

Answer: A. K

Explanation: Lysine (K) is generally not phosphorylated during enzyme regulation. In contrast, serine, threonine, and tyrosine are common targets for phosphorylation, which modulates enzyme activity and cell signaling.

Answer: C. C27H46O

Explanation: Cholesterol is a sterol with the molecular formula C27H46O. Its structure includes a four-ring steroid nucleus and a hydrocarbon tail, playing an essential role in membrane structure and as a precursor for steroid hormones.

Answer: A. Eicosanoids

Explanation: Eicosanoids are bioactive lipid mediators derived from arachidonic acid. They play essential roles in inflammation, immunity, and other cellular signaling pathways, and are produced via enzymatic oxidation.