What is the function of plasmids in prokaryotic cells?

Plasmids serve a significant role in prokaryotic cells by carrying non-essential genes that can be advantageous for survival in specific environments. These small, circular DNA molecules exist independently of the chromosomal DNA and often harbor genes that provide various benefits, such as antibiotic resistance, the ability to metabolize unusual substances, or virulence factors in pathogenic bacteria.

The genes present on plasmids can be transferred between bacteria through processes such as conjugation, which contributes to genetic diversity and the rapid adaptation of bacterial populations to changing conditions. This capability is particularly valuable in competitive or hostile environments, where survival can depend on having certain traits that are not part of the essential genetic toolkit found in the chromosomal DNA.

The other options do not accurately represent the primary role of plasmids. Essential genes necessary for basic growth are typically found in the chromosomal DNA, cell movement is primarily managed by structures like flagella rather than plasmids, and energy storage is a function carried out by molecules like glycogen or lipids, not plasmids.