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This article discusses the cell both as an individual unit and as a contributing part of a larger organism. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself in order to produce succeeding generations. It can be viewed as an enclosed vessel, within which innumerable chemical reactions take place . Sep 05,  · Aug. 29, — A new study presents a technique to identify viruses and bacteria in the human body and quantify injuries to organs by using dead fragments of DNA, called cell-free DNA, . Cell theory. To distinguish individual cells in a piece of tissue or individual bacteria in a sample of liquid required the development of relatively high-powered microscopes, instruments used for magnifying objects otherwise too small to be seen. For more on how microscopes are used in biology today, check out the article on microscopy.


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Cellin biologythe basic membrane-bound unit that cell articles the fundamental molecules of life and of which all living things are composed, cell articles. A single cell is often a complete cell articles in itself, such cell articles a bacterium or cell articles. Other cells acquire specialized functions as they mature.

These cells cooperate with other specialized cells and become the building blocks of large multicellular organisms, such as humans and other animals. Although cells are much larger than atomsthey are still very small.

The smallest known cells are a group of tiny bacteria called mycoplasmas ; some of these single-celled organisms are spheres as small as 0. It would require a sheet of about 10, human cells to cover the head of a pin, and each human organism is composed of more than 30,, cells.

This article discusses the cell both as an individual unit and as a contributing part of a larger organism. As an individual unit, cell articles, the cell is capable of metabolizing its own nutrientssynthesizing many types of molecules, providing its own energy, cell articles, and replicating itself in order to produce succeeding generations, cell articles.

It can be viewed as an enclosed vessel, cell articles, within which innumerable chemical reactions take place simultaneously. These reactions are under very precise control so that they contribute to the life and procreation of the cell. In a multicellular organismcells become specialized to perform different functions through the process of differentiation, cell articles.

In order to do this, cell articles, each cell keeps in constant communication with its neighbours. As it receives nutrients from and expels wastes into its surroundings, it adheres to and cooperates with other cells.

Cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organswhich carry out the functions necessary to sustain the life of an organism. Special emphasis is given in this article to animal cells, with some discussion of the energy-synthesizing processes and extracellular components peculiar to plants, cell articles. For detailed discussion of the biochemistry of plant cells, see photosynthesis.

For a full treatment of the genetic events in the cell nucleus, cell articles, see heredity. A cell is enclosed by a plasma membranewhich forms a selective barrier that allows nutrients to enter and waste products to leave. The interior of the cell articles is organized into many specialized compartments, or organelleseach surrounded by a separate membrane.

One major organellethe nucleuscontains the genetic information necessary for cell growth and reproduction. Each cell contains only one nucleus, whereas other types of organelles are present in multiple copies in the cellular contents, or cytoplasm. Organelles include cell articleswhich are responsible for the energy transactions necessary for cell survival; lysosomeswhich digest unwanted materials within the cell; and the endoplasmic reticulum and the Golgi apparatuswhich play important roles in the internal organization of the cell by synthesizing selected molecules and then processing, sorting, and directing them to their proper locations.

In addition, plant cells contain chloroplastswhich are responsible cell articles photosynthesis, whereby the energy of sunlight is used to convert molecules of carbon dioxide CO 2 and water H 2 O into carbohydrates. Between all these organelles is the space in the cytoplasm called the cytosol. The cytosol contains an organized framework of fibrous molecules that constitute the cytoskeletonwhich cell articles a cell its shape, enables organelles to move within the cell, and provides a mechanism by which the cell itself can move.

The cytosol also contains more than 10, different kinds of molecules that are involved in cellular biosynthesisthe process of making large biological molecules from small ones. Specialized organelles are a characteristic of cell articles of organisms known as eukaryotes.

In contrast, cells of organisms known as prokaryotes do not contain organelles and are generally smaller than eukaryotic cells. However, cell articles, all cells share strong similarities in biochemical cell articles. Cells cell articles a special collection of molecules that are enclosed by a membrane.

These molecules give cells the ability to grow and reproduce. The overall process of cellular reproduction occurs in two steps: cell growth and cell division. During cell growth, the cell ingests certain molecules from its surroundings by selectively carrying them through its cell membrane.

Once inside the cell, these molecules are subjected to the action of highly specialized, large, elaborately folded molecules called enzymes, cell articles. Enzymes act as catalysts by binding to ingested molecules and regulating the rate at which they are chemically altered. These chemical alterations make the molecules more useful to the cell.

Unlike the ingested molecules, catalysts are not chemically altered themselves during the reaction, allowing one catalyst to regulate a specific chemical reaction in many molecules. Biological catalysts create chains of reactions. In other words, a molecule chemically transformed by one catalyst serves as the starting material, or substrate, of a second catalyst and so on. In this way, catalysts use the small cell articles brought into the cell from the outside environment to create increasingly complex reaction products.

These products are used for cell growth and the replication of genetic material. Once the genetic material has been copied and there are sufficient molecules to support cell division, the cell divides to create two daughter cells.

Through many such cycles of cell growth and division, each parent cell can give rise to millions of daughter cells, in the process converting large amounts of inanimate matter into biologically active molecules.

Article Media, cell articles. Info Print Print. Table Of Contents. Submit Feedback. Thank you for your feedback. Written By: Bruce M. Alberts Harvey F, cell articles. Lodish L, cell articles. Andrew Staehelin Wilfred D, cell articles. Stein Michael Cuffe Jonathan Cell articles. Slack …See All Contributors. Facts Matter. Start Your Free Trial Today. Load Next Page. More About. British Society for Cell Biology - What is a cell?

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This article discusses the cell both as an individual unit and as a contributing part of a larger organism. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself in order to produce succeeding generations. It can be viewed as an enclosed vessel, within which innumerable chemical reactions take place . Single-Cell Analysis of Crohn’s Disease Lesions Identifies a Pathogenic Cellular Module Associated with Resistance to Anti-TNF Therapy Jerome C. Martin, Ephraim Kenigsberg. Apr 10,  · Sight for sore eyes. When the embryonic stem cells “speak,” the eye cells “listen.” Their chemical messages persuade the eye cells to turn off the genes that tell them to be cornea cells. Over time, the eye cells become stem cells that can give rise to different types of cells, including nerve cells/