cell

Table of Contents

Introduction & Top Questions
The nature and function of cells
- The molecules of cells
  - The structure of biological molecules
  - Coupled chemical reactions
    - Photosynthesis: the beginning of the food chain
    - ATP: fueling chemical reactions
- The genetic information of cells
  - DNA: the genetic material
  - RNA: replicated from DNA
- The organization of cells
  - Intracellular communication
  - Intercellular communication
The cell membrane
- Chemical composition and membrane structure
  - Membrane lipids
  - Membrane proteins
  - Membrane fluidity
- Transport across the membrane
  - Permeation
  - Membrane channels
  - Facilitated diffusion
    - The glucose transporter
    - The anion transporter
  - Secondary active transport
    - Counter-transport
    - Co-transport
  - Primary active transport
    - The sodium-potassium pump
    - Calcium pumps
    - Hydrogen ion pumps
  - Transport of particles
    - Endocytosis
    - Exocytosis
Internal membranes
- General functions and characteristics
- Cellular organelles and their membranes
  - The vacuole
  - The lysosome
  - Microbodies
  - The endoplasmic reticulum
    - The smooth endoplasmic reticulum
    - The rough endoplasmic reticulum
  - The Golgi apparatus
  - Secretory vesicles
- Sorting of products by chemical receptors
The nucleus
- Structural organization of the nucleus
  - DNA packaging
    - Nucleosomes: the subunits of chromatin
    - Organization of chromatin fibre
  - The nuclear envelope
- Genetic organization of the nucleus
  - The structure of DNA
  - Rearrangement and modification of DNA
- Genetic expression through RNA
  - RNA synthesis
  - Processing of mRNA
- Regulation of genetic expression
  - Regulation of RNA synthesis
  - Regulation of RNA after synthesis
The mitochondrion and the chloroplast
- Mitochondrial and chloroplastic structure
- Metabolic functions
  - The mitochondrion
    - Formation of the electron donors NADH and FADH₂
    - The electron-transport chain
    - The chemiosmotic theory
  - The chloroplast
    - Trapping of light
    - Fixation of carbon dioxide
- Evolutionary origins
  - The mitochondrion and chloroplast as independent entities
  - The endosymbiont hypothesis
The cytoskeleton
- Actin filaments
- Microtubules
- Intermediate filaments
The cell matrix and cell-to-cell communication
- The extracellular matrix
  - Matrix polysaccharides
  - Matrix proteins
  - Cell-matrix interactions
- Intercellular recognition and cell adhesion
  - Tissue and species recognition
  - Cell junctions
    - Adhering junctions
    - Tight junctions
    - Gap junctions
- Cell-to-cell communication via chemical signaling
  - Types of chemical signaling
  - Signal receptors
  - Cellular response
- The plant cell wall
  - Mechanical properties of wall layers
  - Components of the cell wall
    - Cellulose
    - Matrix polysaccharides
    - Proteins
    - Plastics
  - Intercellular communication
    - Plasmodesmata
    - Oligosaccharides with regulatory functions
Cell division and growth
- Duplication of the genetic material
- Cell division
  - Mitosis and cytokinesis
  - Meiosis
- The cell division cycle
  - Controlled proliferation
  - Failure of proliferation control
Cell differentiation
- The differentiated state
- The process of differentiation
- Errors in differentiation
The evolution of cells
- The development of genetic information
- The development of metabolism
The history of cell theory
- Formulation of the theory
  - Early observations
  - The problem of the origin of cells
  - The protoplasm concept
- Contribution of other sciences

References & Edit History Quick Facts & Related Topics

Images & Videos

How are plant cells different from animal cells?

similarities and differences between cells

Consider how a single-celled organism contains the necessary structures to eat, grow, and reproduce

eukaryotic cell

Understand how cell membranes regulate food consumption and waste and how cell walls provide protection

Understand the importance and role of chloroplasts, chlorophyll, grana, thylakoid membranes, and stroma in photosynthesis

Examine the structures adenine, ribose, and a three-phosphate chain in adenosine triphosphate molecule and their role in releasing energy for cellular activities

tricarboxylic acid cycle

For Students

Read Next

H1N1 influenza virus particles. Colorized transmission electron micrograph. Surface proteins on surface of the virus particles shown in black. Influenza flu

10 Ways of Looking at Cells

Cell transport - illustration of a diffusion of liquid molecules through cell membrane. Phospholibid bilayer

Fast Facts about the Cell Membrane

Endoplasmic reticulum. cell biology

6 Cell Organelles

Discover

A Factory Interior, watercolor, pen and gray ink, graphite, and white goache on wove paper by unknown artist, c. 1871-91; in the Yale Center for British Art. Industrial Revolution England

Inventors and Inventions of the Industrial Revolution

Pluto. The Changing Faces of Pluto. Most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003.

10 Important Dates in Pluto History

Stylish light blue jeans on wooden background, closeup of inset pocket

Why Do Jeans Have That Tiny Pocket?

earthquake. Heavily damaged school in the town of Yingxiu after a major earthquake struck China's Sichuan Province on May 12, 2008.

The 6 Deadliest Earthquakes Since 1950

In this aerial photo, structures are damaged and destroyed October 15, 2005 in Balakot, Pakistan. It is estimated that 90% of the city of Balakot was leveled by the earthquake. The death toll in the 7.6 magnitude earthquake that struck northern Pakistan on October 8, 2005 is believed to be 38,000 with at least 1,300 more dead in Indian Kashmir. SEE CONTENT NOTES.

6 of the World’s Deadliest Natural Disasters

Person paying with a credit card using a credit card terminal. Cashless payment, credit card reader

What Is a Cashless Society and How Does It Work?

Albert Einstein in Washington, D.C. c. 1921-1923. Physicist

The Solar Eclipse That Made Albert Einstein a Science Celebrity

cell: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	cell system

Photos and Videos

eukaryotic cell

tricarboxylic acid cycle

messenger RNA; translation

early stages of human development

molecular view of the cell membrane

red blood cells

glycerophospholipid structure

How are plant cells different from animal cells?

similarities and differences between cells

Consider how a single-celled organism contains the necessary structures to eat, grow, and reproduce

Understand how cell membranes regulate food consumption and waste and how cell walls provide protection

Understand the importance and role of chloroplasts, chlorophyll, grana, thylakoid membranes, and stroma in photosynthesis

See All Videos and Images →

Topics

stem cell tissue adipose cell DNA repair membrane cell cycle base excision repair neuroglia cilium flagellum biosphere ecosystem DNA community organ multicellular organism evolution heredity death biology

Dig Deeper: More Articles That Discuss This Topic

Key People

Walther Flemming

German biologist

Lynn Margulis

American biologist

Torbjörn Oskar Caspersson

Swedish cytologist and geneticist

Daniel Mazia

American biologist

Fred H. Gage

American geneticist

Ralph M. Steinman.

Ralph M. Steinman

Canadian immunologist and cell biologist

Günter Blobel

German-American scientist

Ohsumi, Yoshinori

Yoshinori Ohsumi

Japanese biologist

Rothman, James E.

James E. Rothman

American biochemist and cell biologist

Schekman, Randy W.

Randy W. Schekman

American biochemist and cell biologist

Elizabeth Stern

Canadian pathologist

Purkinje, Jan Evangelista

Jan Evangelista Purkinje

Czech physiologist

John Sulston

British biologist

Beneden, Edouard van

Edouard van Beneden

Belgian embryologist and cytologist

Paul Alfred Weiss

American biologist

Albert Claude

Belgian cytologist

George E. Palade

Romanian-born American cell biologist

Keith Roberts Porter

American biologist

Edmund Beecher Wilson

Edmund Beecher Wilson

American biologist

Martin Rodbell.

Martin Rodbell

American biochemist

Quiz

Mechanism of cellular autophagy, illustration for Nobel Prize Award in Medicine 2016. 3D illustration showing fusion of lysosome with autophagosome containing microbes and molecules.

Parts of a Cell Quiz

greylag. Flock of Greylag geese during their winter migration at Bosque del Apache National Refugee, New Mexico. greylag goose (Anser anser)

Biology Bonanza

List

H1N1 influenza virus particles. Colorized transmission electron micrograph. Surface proteins on surface of the virus particles shown in black. Influenza flu

10 Ways of Looking at Cells

Cell transport - illustration of a diffusion of liquid molecules through cell membrane. Phospholibid bilayer

Fast Facts about the Cell Membrane

Endoplasmic reticulum. cell biology

6 Cell Organelles