For biology students, knowing the components of eukaryotic cells and how they work is fundamental to understanding how organisms function. This table provides an overview of the most important eukaryotic cell structures and functions and how to recognize them.
| Structure | Function | How to Recognize |
|---|---|---|
| Cell wall | Rigid boundary around some cells | Outermost boundary in plant, algal, fungal, and bacterial cells. Cells with a cell wall are usually very regular in shape, like they’ve been cut with a cookie cutter. |
| Chloroplasts | Make food, transferring energy from sun to food molecules | Organelles with two membranes and internal stacks of membranes called grana, which look like layers of stripes. |
| Cytoskeleton | Reinforces cell structures; helps move materials around cell | Looks like cables running through the cell. |
| Endoplasmic reticulum (ER) | Rough ER has ribosomes, makes proteins; smooth ER makes lipids | Folded sheets of membrane that ripple off of the nucleus of cells. The rough ER has ribosomes stuck to it, so has a speckled appearance. Smooth ER may look tubular, like coral, and has an unspeckled surface. |
| Golgi | Receives molecules from ER and modifies, tags, and ships them out | Looks like a stack of pancakes surrounded by little membrane spheres. |
| Lysosomes | Break down worn-out cell parts | Small spheres within the cell; may contain partially broken down materials. |
| Mitochondria | Transfer energy from food to useful form for cells (ATP) | Organelles with two membranes. The inner membrane is crinkled into folds called cristae. |
| Nucleus | Houses the genetic material | Largest organelle, surrounded by a double membrane that has little holes in it. May contain dark spots called nucleoli. |
| Plasma membrane | Selective boundary of cell | Outermost boundary in animal cells. Cells that have only a plasma membrane for their boundary may be variable in shape. |
| Ribosomes | Where proteins are made | Look like tiny dots in the cell. May be loose in the cytoplasm or attached to the rough endoplasmic reticulum. |