Develop and use a model to compare prokaryotic and eukaryotic cells and explain how their structures relate to their functions (Louisiana Student Standards for Science, High School Biology, HS-LS1-2).

What this topic is asking

Louisiana's LS1 standards (HS-LS1-2) ask you to model how cells are organized and compare the two fundamental cell types. For LEAP 2025 Biology you should be able to distinguish a prokaryotic cell from a eukaryotic cell, name the structures each does and does not have, and compare plant and animal cells. The test often gives a description or a labeled model of a cell and asks you to classify it, which uses the developing-and-using-models practice.

What all cells have in common

Whatever their type, every cell has four things: a cell membrane that surrounds it and controls what enters and leaves, cytoplasm (the fluid interior where reactions happen), ribosomes (the structures that build proteins), and DNA (the genetic instructions). When the test asks for a structure found in both prokaryotes and eukaryotes, any of these four is correct.

Prokaryotic cells: no nucleus

Because they lack internal membranes, prokaryotic cells are simpler and smaller. They still carry out all of life's processes, just without compartments: their reactions happen in the cytoplasm or at the cell membrane. Many prokaryotes also have a cell wall outside the membrane for support, but the defining feature for the test is the absence of a nucleus.

Eukaryotic cells: a true nucleus and organelles

The membrane-bound organelles are the practical advantage of eukaryotic cells: by keeping processes in separate compartments (for example, releasing energy inside mitochondria), the cell can run many reactions at once without them interfering. This is the structure-and-function theme again, applied at the level of the whole cell.

Plant versus animal cells

Both plant and animal cells are eukaryotic, so both have a nucleus and organelles. The differences are the structures plant cells have that animal cells do not:

• A cell wall outside the membrane, made mostly of cellulose, which gives the plant cell a rigid, fixed shape and support.
• Chloroplasts, the organelles where photosynthesis happens, which animal cells lack because animals do not make their own food.
• A large central vacuole that stores water and helps keep the cell firm (turgid).

Animal cells, by contrast, have only a flexible membrane (no wall), no chloroplasts, and usually only small vacuoles, so they have more varied shapes.

Try this

Q1. State two structures found in all cells, prokaryotic and eukaryotic. [2]

• Cue. Any two of: cell membrane, cytoplasm, ribosomes, DNA.

Q2. A plant cell and an animal cell are both eukaryotic. Name two structures the plant cell has that the animal cell does not, and give a function for each. [2]

• Cue. Cell wall (support and fixed shape) and chloroplast (photosynthesis); a large central vacuole (stores water, keeps the cell turgid) is also acceptable.