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Most cells are only visible under a microscope. Cells emerged on Earth about 4 billion years ago. All cells are capable of replication, protein synthesis, and motility. Cells are broadly categorized into two types: eukaryotic cells, which possess a nucleus, and prokaryotic cells, which lack a nucleus but
Light micrograph of a moss's leaf cells at 400X magnification. The following outline is provided as an overview of and topical guide to cell biology: . Cell biology – A branch of biology that includes study of cells regarding their physiological properties, structure, and function; the organelles they contain; interactions with their environment; and their life cycle, division, and death.
Cellular compartments in cell biology comprise all of the closed parts within the cytosol of a eukaryotic cell, usually surrounded by a single or double lipid layer membrane. These compartments are often, but not always, defined as membrane-bound organelles. The formation of cellular compartments is called compartmentalization.
A drawing of a prokaryotic cell. There are two fundamental classifications of cells: prokaryotic and eukaryotic. Prokaryotic cells are distinguished from eukaryotic cells by the absence of a cell nucleus or other membrane-bound organelle. [10] Prokaryotic cells are much smaller than eukaryotic cells, making them the smallest form of life. [11]
Diagram of a prokaryotic cell, a bacterium with a flagellum. A prokaryote (/ p r oʊ ˈ k ær i oʊ t,-ə t /; less commonly spelled procaryote) [1] is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. [2]
Some eukaryotic cells also use flagella—and they can be found in some protists and plants as well as animal cells. Eukaryotic flagella are complex cellular projections that lash back and forth, rather than in a circular motion. Prokaryotic flagella use a rotary motor, and the eukaryotic flagella use a complex sliding filament system.
Cell physiology is the biological study of the activities that take place in a cell to keep it alive. The term physiology refers to normal functions in a living organism. [1] Animal cells, plant cells and microorganism cells show similarities in their functions even though they vary in structure. [2] [page needed]
For the bacterial (prokaryotic) cells that are bounded by a single cell membrane the term "monoderm bacteria" or "monoderm prokaryotes" has been proposed. [ 4 ] [ 8 ] In contrast to gram-positive bacteria, all archetypical Gram-negative bacteria are bounded by a cytoplasmic membrane as well as an outer cell membrane; they contain only a thin ...