What is the function of the capsule in prokaryotic cells?

The capsule in prokaryotic cells functions primarily as a protective structure. It plays a crucial role in safeguarding the cell against desiccation or drying out, which is essential for maintaining cell viability in variable environments. Additionally, the capsule serves as a barrier against phagocytosis, a process by which immune cells engulf and destroy foreign entities. By making the bacterium less recognizable to the host’s immune system, the capsule enhances the organism's virulence and ability to cause disease.

The capsule is typically composed of polysaccharides or polypeptides, contributing to its protective properties and making it more difficult for the immune system to detect. This structural feature is especially important for pathogenic bacteria, which rely on the capsule to evade immune responses in the host.

In contrast, the other functions listed are attributed to different cellular components or processes within the prokaryotic cell. Energy production occurs primarily in the cytoplasmic membrane through processes such as cellular respiration or fermentation, whereas DNA replication is managed by specific enzymes and occurs at the origin of replication in the cell. Protein synthesis takes place at the ribosomes, where messenger RNA is translated into polypeptide chains. Therefore, the capsule's main role is centered around protection, aligning with the chosen answer.