Cell | Definition, Types, Functions, Diagram, Division, Theory, & Facts ...
Dec 1, 2025 · What is a cell? A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all …
What is a cell? | Britannica
A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all living things.
Structure and types of cells | Britannica
cell, In biology, the basic unit of which all living things are composed; the smallest structural unit of living matter that is able to function independently. A single cell can be a complete organism in itself, as in …
Cell membrane | Definition, Function, & Structure | Britannica
Nov 27, 2025 · Enclosed by the cell membrane are the cell’s constituents, which include large, water-soluble, highly charged molecules such as proteins, nucleic acids, carbohydrates, and substances …
cell - Kids | Britannica Kids | Homework Help
Every organism, or living thing, is made up of structures called cells. The cell is the smallest unit with the basic properties of life. Some tiny organisms, such as bacteria…
Cell theory | Definition, History, Importance, Scientists, First ...
Nov 25, 2025 · cell theory, fundamental scientific theory of biology according to which cells are held to be the basic units of all living tissues.
Cell cycle | Description, Stages, & Checkpoints | Britannica
Dec 4, 2025 · The cell cycle is a four-stage process in which the cell increases in size, copies its DNA, prepares to divide, and divides. Learn more about the cell cycle and the proteins that regulate its …
Prokaryote | Definition, Example, & Facts | Britannica
Nov 20, 2025 · The prokaryotic cell membrane is made up of phospholipids and constitutes the cell’s primary osmotic barrier. The cytoplasm contains ribosomes, which carry out protein synthesis, and a …
Membrane | Definition, Structure, & Functions | Britannica
Enclosed by the cell membrane are the cell’s constituents, which include large, water-soluble, highly charged molecules such as proteins, nucleic acids, carbohydrates, and substances involved in …
Ribosome | Definition, Function, Formation, Role, Importance, & Facts ...
Nov 25, 2025 · Ribosome, particle that is present in large numbers in all living cells and serves as the site of protein synthesis. Ribosomes occur both as free particles in prokaryotic and eukaryotic cells …