![]() ![]() ![]() The chemical reactions that take place in living cells are similar as well. Get a Britannica Premium subscription and gain access to exclusive content. With minor exceptions, the genetic code used by all living organisms is the same. The replication of the genetic material in these organisms must, however, pass through a DNA phase. Some primitive life-forms, however, use RNA (ribonucleic acid a nucleic acid differing from DNA in containing the sugar ribose instead of the sugar deoxyribose and the base uracil instead of the base thymine) in place of DNA as a primary carrier of genetic information. ![]() Just as the Morse Code consists of three simple signals-a dash, a dot, and a space-the precise arrangement of which suffices to convey coded messages, so the precise arrangement of the bases in DNA contains and conveys the information for the synthesis and assembly of cell components. Only four bases are used in synthesizing DNA: adenine, guanine, cytosine, and thymine. For example, hereditary information is encoded in a specific sequence of bases that make up the DNA (deoxyribonucleic acid) molecule in the nucleus of each cell. There is the same unity among cells of all types in the manner in which living organisms preserve their individuality and transmit it to their offspring. Moreover, those portions of protein molecules involved in performing similar functions in different organisms often comprise the same sequences of amino acids. Proteins are assembled from some 20 amino acids, and, just as the 26 letters of the alphabet can be assembled in specific ways to form words of various lengths and meanings, so may tens or even hundreds of the 20 amino-acid “letters” be joined to form specific proteins. Thus, all living matter is made up of large molecules called proteins, which provide support and coordinated movement, as well as storage and transport of small molecules, and, as catalysts, enable chemical reactions to take place rapidly and specifically under mild temperature, relatively low concentration, and neutral conditions (i.e., neither acidic nor basic). This is true for animals, plants, fungi, or bacteria where variations occur (such as, for example, in the secretion of antibodies by some molds), the variant processes are but variations on common themes. The physical and chemical properties of the components of living things dealt with in this article are found in the articles carbohydrate cell hormone lipid photosynthesis and protein.īiology Bonanza A summary of metabolism The unity of lifeĪt the cellular level of organization, the main chemical processes of all living matter are similar, if not identical. Hundreds of coordinated, multistep reactions, fueled by energy obtained from nutrients and/or solar energy, ultimately convert readily available materials into the molecules required for growth and maintenance. The answers to these questions lie in the enzyme-mediated chemical reactions that take place in living matter (metabolism). But how do living organisms-or, their cells-extract energy from their environments, and how do cells use this energy to synthesize and assemble the components from which the cells are made? Living organisms are unique in that they can extract energy from their environments and use it to carry out activities such as movement, growth and development, and reproduction. Metabolism, the sum of the chemical reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
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