Cell | Definition, Types, Functions, Diagram, Division, Theory,
2025年1月6日 · Cell, in biology, the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed. A single cell may be a complete organism in itself, such as a bacterium, or it may acquire a specialized function, becoming a building block of a multicellular organism.
Cell membrane | Definition, Function, & Structure | Britannica
2024年11月18日 · Cell membrane, thin membrane that surrounds every living cell. The cell membrane functions as a barrier, keeping cell constituents in and unwanted substances out, and as a gate, allowing transport into the cell of essential nutrients and movement from the cell of waste products.
Cell - Structure, Organelles, Metabolism | Britannica
2025年1月6日 · Cell - Structure, Organelles, Metabolism: Like the cell membrane, membranes of some organelles contain transport proteins, or permeases, that allow chemical communication between organelles.
Human body | Organs, Systems, Structure, Diagram, & Facts
2024年12月10日 · The cell is the basic living unit of the human body—indeed, of all organisms. The human body consists of trillions of cells, each capable of growth, metabolism, response to stimuli, and, with some exceptions, reproduction. Although there are some 200 different types of cells in the body, these can be grouped into four basic classes.
Structure and types of cells | Britannica - Encyclopedia Britannica
A single cell can be a complete organism in itself, as in bacteria and protozoans. Groups of specialized cells are organized into tissues and organs in multicellular organisms such as higher plants and animals. There are two distinct types of cells: prokaryotic cells and eukaryotic cells.
Mitochondrion | Definition, Function, Structure, & Facts | Britannica
2024年11月29日 · mitochondrion, membrane-bound organelle found in the cytoplasm of almost all eukaryotic cells (cells with clearly defined nuclei), the primary function of which is to generate large quantities of energy in the form of adenosine triphosphate (ATP).
cell - Students | Britannica Kids | Homework Help
The smallest unit of living matter that can exist by itself is the cell. Some organisms, such as bacteria, consist of only a single cell. Others, such as large animals and trees, are composed of many billions of cells. Each human is made up of trillions of cells.
cell - Kids | Britannica Kids | Homework Help
Most cells have three main parts—the cell membrane, the cytoplasm, and the nucleus. The cell membrane is like the skin of the cell. The cytoplasm performs many functions to keep the cell alive.
Nucleus | Definition, Function, Structure, & Facts | Britannica
2024年12月16日 · Nucleus, in biology, a specialized structure occurring in most cells (except bacteria and blue-green algae) and separated from the rest of the cell by a double layer, the nuclear membrane. The nucleus controls and regulates the activities of the cell (e.g., growth and metabolism) and carries the genes.
Golgi apparatus | Definition, Function, Location, & Facts | Britannica
2024年11月27日 · The Golgi apparatus, also called Golgi complex or Golgi body, is a membrane-bound organelle found in eukaryotic cells (cells with clearly defined nuclei) that is made up of a series of flattened stacked pouches called cisternae.