Construct explanations comparing prokaryotic and eukaryotic cells in terms of their structures and relative complexity (North Carolina Standard Course of Study, Biology, LS.Bio.1).

What this topic is asking

North Carolina LS.Bio.1 asks you to compare prokaryotic and eukaryotic cells by structure and complexity. For the Biology EOC that means knowing the one defining difference (a true nucleus and membrane-bound organelles), the features the two types share, and the typical differences in size and organization. Items often show a labeled cell or a short description and ask you to classify it, so use the clues rather than guessing.

What all cells share

Before the differences, fix what every cell has, because the EOC uses these as the "shared feature" answers.

• A cell membrane (plasma membrane) that controls what enters and leaves.
• Cytoplasm, the watery interior where reactions happen.
• Ribosomes, the structures that build proteins.
• DNA, the genetic material that carries the instructions.

Because both cell types have all four, a question that asks for the difference will never be "a cell membrane" or "DNA." Those are traps. The real difference is how the DNA and the rest of the machinery are organized.

The defining difference: the nucleus

Membrane-bound organelles let a eukaryotic cell compartmentalize its work, keeping different chemical processes in separate spaces (energy release in mitochondria, photosynthesis in chloroplasts, protein processing in the endoplasmic reticulum and Golgi). A prokaryote does all of its chemistry in one open compartment, which works because the cell is small and the processes are simpler.

Size and complexity

Prokaryotic cells are typically 1 to 5 micrometers across; eukaryotic cells are typically 10 to 100 micrometers, often around ten times larger in each dimension. Size matters because a small cell has a high surface-area-to-volume ratio, so materials diffuse in and out fast enough without internal transport systems. As cells get larger, compartments and transport networks become necessary, which is part of why eukaryotic cells are more complex.

In organization, all prokaryotes are bacteria and archaea, and they are usually unicellular. Eukaryotes include the animals, plants, fungi, and protists, and they can be unicellular (yeast, amoeba) or multicellular (you). A common EOC mistake is to assume eukaryotic always means multicellular; many eukaryotes are single cells.

Try this

Q1. Name two features found in a eukaryotic cell but not a prokaryotic cell. [2]

• Cue. A membrane-bound nucleus and membrane-bound organelles (for example mitochondria or endoplasmic reticulum).

Q2. Explain why prokaryotic cells can manage without internal transport systems but large eukaryotic cells cannot. [2]

• Cue. Prokaryotes are small with a high surface-area-to-volume ratio, so diffusion is fast enough; larger eukaryotic cells need compartments and transport to move materials over greater distances.