Which statement best describes the function of the cytoskeleton?

A. riboflavin: Certain microorganisms, such as fungi and bacteria, are used industrially to synthesize riboflavin (vitamin B2). Microbial fermentation allows large-scale production of this essential vitamin for dietary supplements and food fortification. The use of microbes provides a cost-effective and scalable method compared to chemical synthesis.

B. acetone: Acetone can be produced through microbial fermentation, particularly using Clostridium species in the acetone-butanol-ethanol (ABE) fermentation process. This method was historically important for industrial solvent production before petrochemical methods became widespread. Microbial synthesis allows renewable production from carbohydrate sources.

C. insulin: Recombinant DNA technology uses genetically engineered bacteria or yeast to produce human insulin. Microbes are transformed with the insulin gene, allowing high-yield production of biologically active insulin for diabetes treatment. This method replaced extraction from animal pancreases, improving safety and scalability.

D. aspirin: Aspirin (acetylsalicylic acid) is chemically synthesized from salicylic acid and acetic anhydride. Microorganisms are not typically used in its industrial production, making this an exception among commonly microbially produced compounds.

E. riboflavin, acetone and insulin: Microorganisms are commercially exploited to synthesize riboflavin, acetone, and insulin through fermentation or recombinant DNA technology. These processes demonstrate the economic and therapeutic benefits of microbial biotechnology in vitamins, solvents, and pharmaceuticals.

A. Flagella: Flagella are whip-like appendages used for motility and are commonly found in prokaryotic cells such as bacteria. They are anchored in the cell membrane and cell wall and function to propel the cell toward nutrients or away from harmful stimuli. Their presence is consistent with prokaryotic structure and physiology.

B. Nucleus: Prokaryotic cells lack a membrane-bound nucleus. Instead, their genetic material exists as a single circular DNA molecule located in the nucleoid region of the cytoplasm. The absence of a nucleus is a defining feature that differentiates prokaryotes from eukaryotes.

C. Ribosomes: Prokaryotic cells contain ribosomes, typically 70S in size, which are responsible for protein synthesis. These ribosomes are dispersed throughout the cytoplasm and facilitate translation of messenger RNA into functional proteins.

D. Cell wall: Most prokaryotes possess a rigid cell wall that maintains cell shape, provides structural support, and protects against osmotic stress. In bacteria, the cell wall is primarily composed of peptidoglycan, which differs structurally from eukaryotic cell walls.

E. Cell membrane: The plasma membrane is a phospholipid bilayer that encloses the cytoplasm of prokaryotic cells. It regulates the movement of substances in and out of the cell and houses proteins essential for energy production, nutrient transport, and signal transduction.