Glossary
eukaryote
A eukaryote is a cell with a true nucleus and membrane-bound organelles — the cells of plants, animals, fungi and protists.
A eukaryote is a cell that keeps its DNA inside a nucleus and does its work in membrane-bound compartments. The nucleus holds the chromosomes and is the reason the name exists — karyon is the kernel. Around it sit the organelles: mitochondria, where energy is released from food; the endoplasmic reticulum and the Golgi apparatus, where proteins are made and packaged; lysosomes, where material is broken down; and, in plants, chloroplasts, where light is captured. Each is a membrane-bound space with its own conditions, which is what lets one cell carry out reactions that would interfere with each other in a single open room. That compartmental arrangement is why eukaryotic cells are far larger than prokaryotic ones and can build tissues. Plant, animal, fungal and protist cells are all eukaryotic; the differences among them are which organelles are present.
Taught in
Related terms
- prokaryote — A prokaryote is a cell with no nucleus and no membrane-bound organelles — its DNA sits loose in the cytoplasm, as it does in bacteria.
- cell theory — The cell theory is the claim that every living thing is made of cells, that the cell is the basic unit of structure and function, and that cells come from existing cells.
- phospholipid bilayer — The phospholipid bilayer is the two-layer sheet that makes up every cell membrane, with water-loving heads facing out and water-fearing tails facing in.
Source: The biology guide in this course: its genetics definitions follow the National Human Genome Research Institute's Talking Glossary of Genomic and Genetic Terms, and its process descriptions follow the US National Cancer Institute's SEER Training Modules. Both are US federal government material, not subject to copyright in the United States. The microbiology entries — the bacterial cell, the Gram stain and the chain of infection — were written for this course from the infection-control guidance the biology guide's own source list names (US Centers for Disease Control and Prevention), which the genetics glossary does not cover. The definitions above are written for this course in our own words. (NHGRI Talking Glossary accessed 2026-10-26; definitions written 2026-10-27; the CDC basis for the microbiology entries — Principles of Epidemiology in Public Health Practice, third edition — accessed 2026-10-28, the date the biology guide's own source list records)