Understand the difference between prokaryotic and eukaryotic cells: Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and organelles.
Identify the organisms listed: Saccharomyces cerevisiae (yeast) is a eukaryote (fungus), human skeletal muscle cells are eukaryotic animal cells, and plant leaf mesophyll cells are eukaryotic plant cells.
Recognize that Escherichia coli is a bacterium, and bacteria are classified as prokaryotes because they do not have a nucleus or membrane-bound organelles.
Conclude that among the options, Escherichia coli is the only prokaryotic cell, while the others are eukaryotic cells.
Summarize that the key characteristic to identify a prokaryotic cell is the absence of a nucleus and membrane-bound organelles, which applies to Escherichia coli.