Bioenergetics

Adenosine 5-triphosphate (ATP) The carrier of free energy in cells. Bioenergetics The study of energy relationships in living systems. Chloroplasts The sites of photosynthesis in green plants. Ion transport The movement of ions across biological membranes. Metabolism The total of all reactions that occur in cells. Catabolic metabolism is generally degradative and ex-ergonic, whereas anabolic […]

Bioenergetics

BIOENERGETICS, an amalgamation of the term biological energetics, is the branch of biology and biochemistry that is concerned with how organisms extract energy from their environment and with how energy is used to fuel the myriad of life’s endergonic processes. Organisms may be usefully divided into two broad groups with respect to how they satisfy […]

CATABOLIC METABOLISM: THE SYNTHESIS OF ATP (Bioenergetics)

Metabolism may be defined as the total of all the chemical reactions that occur in organisms. Green plants can synthesize all the thousands of compounds they contain from carbon dioxide, water, and inorganic nutrients. The discussion of the complicated topic of metabolism is somewhat simplified by separation of the subject into two areas—catabolic and anabolic […]

PHOTOSYNTHESIS (Bioenergetics)

From a purely thermodynamic standpoint, life is an improbable event. Consider, for example, the complex structures of organisms, not only at the macroscopic level, but also at the microscopic and atomic levels. These ordered structures can be formed and maintained only by the expenditure of energy. Within the ecosystem that we call the earth, the […]

ORIGIN OF MITOCHONDRIA AND CHLOROPLASTS (Bioenergetics)

In animal, yeast, and fungal cells, DNA is present in two organelles, the nucleus and the mitochondria. In plant and algal cells, DNA is present in plastids (of which chloro-plasts are one example) as well as in mitochondria and the nucleus. Unlike the DNA in the nucleus, which is packaged into chromosomes, plastid DNA and […]

ILLUSTRATIONS OF THE USES OF ATP: ION TRANSPORT, BIOSYNTHESIS, AND MOTILITY (Bioenergetics)

ATP powers most of the endergonic processes in cells. How the potential energy of the phosphoanhydride bond of ATP may be used to drive otherwise unfavorable reactions (Fig. 11) is discussed in this section. This discussion focuses on three major uses of ATP: the generation of ion gradients, biosynthesis, and movement. A. Ion Transport The […]

CONCLUDING STATEMENTS (Bioenergetics)

There are two aspects of bioenergetics that we want to emphasize at the end of this article. These are the dependence of life on photosynthesis and the diversity of energy interconversions in living systems. Photosynthesis is the only major biological process that uses a source of energy, sunlight, from outside the earth’s environment to convert […]