cell and types of cell


The cell (from Latin cella, meaning "small room") is the basic structural, functional, and biological unit of all known organisms. A cell is the smallest unit of life. Cells are often called the "building blocks of life". The study of cells is called cell biology, cellular biology, or cytology.

Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids.[2] Most plant and animal cells are only visible under a light microscope, with dimensions between 1 and 100 micrometres.[3] Electron microscopy gives a much higher resolution showing greatly detailed cell structure. Organisms can be classified as unicellular (consisting of a single cell such as bacteria) or multicellular (including plants and animals).[4] Most unicellular organisms are classed as microorganisms.

Comparison of features of prokaryotic and eukaryotic cells
  Prokaryotes Eukaryotes
Typical organisms bacteriaarchaea protistsfungiplantsanimals
Typical size ~ 1–5 μm[18] ~ 10–100 μm[18]
Type of nucleus nucleoid region; no true nucleus true nucleus with double membrane
DNA circular (usually) linear molecules (chromosomes) with histone proteins
RNA/protein synthesis coupled in the cytoplasm RNA synthesis in the nucleus
protein synthesis in the cytoplasm
Ribosomes 50S and 30S 60S and 40S
Cytoplasmic structure very few structures highly structured by endomembranes and a cytoskeleton
Cell movement flagella made of flagellin flagella and cilia containing microtubuleslamellipodia and filopodia containing actin
Mitochondria none one to several thousand
Chloroplasts none in algae and plants
Organization usually single cells single cells, colonies, higher multicellular organisms with specialized cells
Cell division binary fission (simple division) mitosis (fission or budding)
Chromosomes single chromosome more than one chromosome
Membranes cell membrane Cell membrane and membrane-bound organelles

Subcellular components

All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell. Inside the membrane, the cytoplasm takes up most of the cell's volume. All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. This article lists these primary cellular components, then briefly describes their function.