Cell biology
McGraw-Hill Science & Technology Encyclopedia:
Top
Cell biology
The study of the activities, functions, properties, and structures of cells. Cells were discovered in the middle of the seventeenth century after the microscope was invented. In the following two centuries, with steadily improved microscopes, cells were studied in a wide variety of plants, animals, and microorganisms, leading to the discovery of the cell nucleus and several other major cell parts. By the 1830s biologists recognized that all organisms are composed of cells, a realization that is now known as the Cell Doctrine. The Cell Doctrine constitutes the first major tenet upon which the contemporary science of cell biology is founded. By the late 1800s biologists had established that cells do not arise de novo, but come only by cell division, that is, division of a preexisting cell into two daughter cells. This is the second major tenet upon which the modern study of cells is based. See also Microscope.
By the end of the nineteenth century chromosomes had been discovered, and biologists had described mitosis—the distribution at cell division of chromosomes to daughter cells. Subsequent studies showed that the chromosomes contain genes and that mitosis distributes a copy of every chromosome and hence every gene to each daughter cell during cell division. This established the basis of cell heredity and ultimately the basis of heredity in multicellular organisms. See also Chromosome; Mitosis.
Microscope studies established that some kinds of organisms are composed of a single cell and some, such as plants and animals, are made up of many cells—usually many billions. Unicellular organisms are the bacteria, protozoa, some fungi, and some algae. All other organisms are multicellular. An adult human, for example, consists of about 200 cell types that collectively amount to more than 1014 cells.
All modern research recognizes that in both unicellular and multicellular organisms the cell is the fundamental unit, housing the genetic material and the biochemical organization that account for the existence of life. Many millions of different species of cells exist on Earth. Cells as different as a bacterium, an ameba, a plant leaf cell, and a human liver cell appear to be so unrelated in structure and life-style that they might seem to have little in common; however, the study of cells has shown that the similarities among these diverse cell types are more profound than the differences. These studies have established a modern set of tenets that bring unity to the study of many diverse cell types. These tenets are: (1) All cells store information in genes made of deoxyribonucleic acid (DNA). (2) The genetic code used in the genes is the same in all species of cells. (3) All cells decode the genes in their DNA by a ribonucleic acid (RNA) system that translates genetic information into proteins. (4) All cells synthesize proteins by using a structure called the ribosome. (5) Proteins govern the activities, functions, and structures in all cells. (6) All cells need energy to operate; all use the molecule adenosine triphosphate (ATP) as the currency for transfer of energy from energy sources to energy needs. (7) All cells are enclosed by a plasma membrane composed of lipid and protein molecules. See also Genetics; Ribosomes.
In the twentieth century the study of cells, which had been dominated for more than 200 years by microscopy, has been enormously expanded with many other experimental methods. The breaking open of a large mass of cells and the separation of released cell parts into pure fractions led to the discovery of functions contributed by different structures and organelles.
Contemporary research in cell biology is concerned with many problems of cell operation and behavior. Cell reproduction is of special concern because it is essential for the survival of all unicellular and multicellular forms of life. Cell reproduction is the means by which a single cell, the fertilized egg, can give rise to the trillions of cells in an adult multicellular organism. Disrupted control of cell reproduction, resulting in accumulation of disorganized masses of functionally useless cells, is the essence of cancer. Indeed, all diseases ultimately result from the death or misfunctioning of one or another group of cells in a plant or animal. The study of cells pervades all areas of medical research and medical treatment. Great advances have been made in learning how cells of the immune system combat infection, and the nature of their failure to resist the acquired immune deficiency syndrome (AIDS) virus. See also Acquired immune deficiency syndrome (AIDS); Cancer (medicine); Cell senescence and death.
The development of methods to grow plant and animal cells in culture has provided new ways to study cells free of the experimental complications encountered with intact plants and animals. Cell culture has greatly facilitated analysis of abnormal cells, including transformation of normal cells into cancer cells. Cultured cells are also used extensively to study cell differentiation, cell aging, cell movement, and many other cell functions. See also Tissue culture.
American Heritage Stedman's Medical Dictionary:
Top
cellular biology
n.
The study of the molecular or chemical interactions of biological phenomena.
Wikipedia on Answers.com:
Top
Cell biology
Not to be confused with Cell (biology).
"Cell research" redirects here. For the journal, see Cell Research (journal).
 |
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2011) |
Cell biology (formerly cytology, from the Greek kytos, "contain") is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level. Cell biology research encompasses both the great diversity of single-celled organisms like bacteria and protozoa, as well as the many specialized cells in multicellular organisms such as humans.
Knowing the components of cells and how cells work is fundamental to all biological sciences. Appreciating the similarities and differences between cell types is particularly important to the fields of cell and molecular biology as well as to biomedical fields such as cancer research and developmental biology. These fundamental similarities and differences provide a unifying theme, sometimes allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types. Therefore, research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology.
|
Contents
|
Processes
Movement of proteins
Each type of protein is usually sent to a particular part of the cell. An important part of cell biology is the investigation of molecular mechanisms by which proteins are moved to different places inside cells or secreted from cells.
Most proteins are synthesized by ribosomes in the rough endoplasmic reticulum.Ribosomes contain the nucleic acid RNA, which assembles and joins amino acids to make proteins. They can be found alone or in groups within the cytoplasm as well as on the RER. This process is known as protein biosynthesis. Biosynthesis (also called biogenesis) is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products (also simply known as protein translation). Some proteins, such as those to be incorporated in membranes (known as membrane proteins), are transported into the "rough" endoplasmic reticulum (ER) during synthesis. This process can be followed by transportation and processing in the Golgi apparatus. The Golgi apparatus is a large organelle that processes proteins and prepares them for use both inside and outside the cell. The Golgi apparatus is somewhat like a post office. It receives items (proteins from the ER), packages and labels them, and then sends them on to their destinations (to different parts of the cell or to the cell membrane for transport out of the cell).[1] From the Golgi, membrane proteins can move to the plasma membrane, to other sub-cellular compartments, or they can be secreted from the cell. The ER and Golgi can be thought of as the "membrane protein synthesis compartment" and the "membrane protein processing compartment", respectively. There is a semi-constant flux of proteins through these compartments. ER and Golgi-resident proteins associate with other proteins but remain in their respective compartments. Other proteins "flow" through the ER and Golgi to the plasma membrane. Motor proteins transport membrane protein-containing vesicles along cytoskeletal tracks to distant parts of cells such as axon terminals.
Some proteins that are made in the cytoplasm contain structural features that target them for transport into mitochondria or the nucleus. Some mitochondrial proteins are made inside mitochondria and are coded for by mitochondrial DNA. In plants, chloroplasts also make some cell proteins.
Extracellular and cell surface proteins destined to be degraded can move back into intracellular compartments upon being incorporated into endocytosed vesicles some of which fuse with lysosomes where the proteins are broken down to their individual amino acids. The degradation of some membrane proteins begins while still at the cell surface when they are separated by secretases. Proteins that function in the cytoplasm are often degraded by proteasomes.
Other cellular processes
- Active transport and Passive transport - Movement of molecules into and out of cells.
- Autophagy - The process whereby cells "eat" their own internal components or microbial invaders.
- Adhesion - Holding together cells and tissues.
- Reproduction - Made possible by the combination of sperm made in the testiculi (contained in some male cells' nuclei) and the egg made in the ovary (contained in the nucleus of a female cell). When the sperm breaks through the hard outer shell of the egg a new cell embryo is formed, which, in humans, grows to full size in 9 months.
- Cell movement: Chemotaxis, Contraction, cilia and flagella.
- Cell signaling - Regulation of cell behavior by signals from outside.
- DNA repair and Cell death
- Metabolism: Glycolysis, respiration, Photosynthesis
- Transcription and mRNA splicing - gene expression.
Internal cellular structures
- Chloroplast - key organelle for photosynthesis (only found in plant cells)
- Cilia - motile microtubule-containing structures of eukaryotes
- Cytoplasm - contents of the main fluid-filled space inside cells
- Cytoskeleton - protein filaments inside cells
- Endoplasmic reticulum - major site of membrane protein synthesis
- Flagella - motile structures of bacteria, archaea and eukaryotes
- Golgi apparatus - site of protein glycosylation in the endomembrane system
- Lipid bilayer - fundamental organizational structure of cell membranes
- Lysosome - break down cellular waste products and debris into simple compounds (only found in animal cells)
- Membrane lipid and protein barrier
- Mitochondrion - major energy-producing organelle by releasing it in the form of ATP
- Nucleus - holds most of the DNA of eukaryotic cells and controls all cellular activities
- Organelle - term used for major subcellular structures
- Ribosome - RNA and protein complex required for protein synthesis in cells
- Vesicle - small membrane-bounded spheres inside cells
Techniques used to study cells
Cells may be observed under the microscope. This includes the Optical Microscope, Transmission Electron Microscope, Scanning Electron Microscope, Fluorescence Microscope, and by Confocal Microscopy.
Several different techniques exist to study cells are
- Cell culture is the basic technique of growing cells in a laboratory independent of an organism.
- Immunostaining, also known as immunohistochemistry, is a specialized histological method used to localize proteins in cells or tissue slices. Unlike regular histology, which uses stains to identify cells, cellular components or protein classes, immunostaining requires the reaction of an antibody directed against the protein of interest within the tissue or cell. Through the use of proper controls and published protocols (need to add reference links here), specificity of the antibody-antigen reaction can be achieved. Once this complex is formed, it is identified via either a "tag" attached directly to the antibody, or added in an additional technical step. Commonly used "tags" include fluorophores or enzymes. In the case of the former, detection of the location of the "immuno-stained" protein occurs via fluorescence microscopy. With an enzymatic tag, such as horse radish peroxidase, a chemical reaction is carried out that results in a dark color in the location of the protein of interest. This darkened pattern is then detected using light microscopy.
- Computational genomics is used to find patterns in genomic information [2]
- DNA microarrays identify changes in transcript levels between different experimental conditions.
- Gene knockdown mutates a selected gene.
- In situ hybridization shows which cells are expressing a particular RNA transcript.
- PCR can be used to determine how many copies of a gene are present in a cell.
- Transfection introduces a new gene into a cell, usually an expression construct
Purification of cells and their parts Purification may be performed using the following methods:
- Cell fractionation
- Release of cellular organelles by disruption of cells.
- Separation of different organelles by centrifugation.
- Flow cytometry
- Immunoprecipitation
- Proteins extracted from cell membranes by detergents and salts or other kinds of chemicals.
See also
 |
Wikimedia Commons has media related to: Cell biology |
Main article: Outline of cell biology
- Cell disruption
- Cellular microbiology
- Institute of Molecular and Cell Biology (disambiguation)
- Prokaryotic cell
- The American Society for Cell Biology
- Cell physiology
Notable cell biologists
- Peter Agre
- Günter Blobel
- Geoffrey M. Cooper
- Christian de Duve
- Robert Hooke
- H. Robert Horvitz
- Marc Kirschner
- Anton van Leeuwenhoek
- Ira Mellman
- Peter D. Mitchell
- Paul Nurse
- George Emil Palade
- Keith R. Porter
- Jan Evangelista Purkyně
- Ray Rappaport
- Michael Swann
- Roger Tsien
- Edmund Beecher Wilson
- Kenneth R. Miller
References
- Cell and Molecular Biology by Karp 5th Ed., ISBN 0-471-46580-1
This article incorporates public domain material from the NCBI document "Science Primer".
External links
 |
Wikibooks has more on the topic of |
 |
Wikiversity has learning materials about Cell biology |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Post a question - any question - to the WikiAnswers community:
Copyrights:
McGraw-Hill Science & Technology Encyclopedia
McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.
Read more
American Heritage Stedman's Medical Dictionary
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company.
Read more
Mentioned in
acetyl-CoA pathway
(cell biology)
adipocyte
(cell biology)
akaryote
(cell and molecular biology)
meiocyte
(cell and molecular biology)
anastral
(cell and molecular biology)
» More