Final answer:
The eukaryotic cell's proteome is larger than its genome primarily due to alternative splicing, a process that generates multiple protein isoforms from a single gene.
Step-by-step explanation:
The proteome of a eukaryotic cell is usually much larger than its genome because of a process known as alternative splicing. This mechanism allows a single gene to produce multiple proteins by splicing the mRNA transcript in different ways, resulting in many different protein isoforms.
These isoforms can also play different roles in various tissues or under different conditions, increasing proteome diversity without the need to expand the size of the genome. This splicing process showcases one of the complexities of eukaryotic gene regulation.
Eukaryotic genomes also have the challenge of coordinating more genes compared to prokaryotes, and gene expression can be regulated at multiple levels due to the sophisticated packaging of their genome.