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Metabolism is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism.
In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reactions catalyzed by enzymes. In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. However, side products are considered waste and removed from the cell.
Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin.
A heterotroph is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers. Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists, and many parasitic plants. The term heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition. The term is now used in many fields, such as ecology, in describing the food chain.
Cellular respiration is the process by which biological fuels are oxidized in the presence of an inorganic electron acceptor, such as oxygen, to drive the bulk production of adenosine triphosphate (ATP), which contains energy. Cellular respiration may be described as a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from nutrients into ATP, and then release waste products.
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.
The metabolic theory of ecology (MTE) is the ecological component of the more general Metabolic Scaling Theory and Kleiber's law. It posits that the metabolic rate of organisms is the fundamental biological rate that governs most observed patterns in ecology. MTE is part of a larger set of theory known as metabolic scaling theory that attempts to provide a unified theory for the importance of metabolism in driving pattern and process in biology from the level of cells all the way to the biosphere.
The following outline is provided as an overview of and topical guide to biochemistry:
The dynamic energy budget (DEB) theory is a formal metabolic theory which provides a single quantitative framework to dynamically describe the aspects of metabolism of all living organisms at the individual level, based on assumptions about energy uptake, storage, and utilization of various substances. The DEB theory adheres to stringent thermodynamic principles, is motivated by universally observed patterns, is non-species specific, and links different levels of biological organization as prescribed by the implications of energetics. Models based on the DEB theory have been successfully applied to over 1000 species with real-life applications ranging from conservation, aquaculture, general ecology, and ecotoxicology. The theory is contributing to the theoretical underpinning of the emerging field of metabolic ecology.
The respiratory quotient is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the body to oxygen consumed by the body, when the body is in a steady state. Such measurements, like measurements of oxygen uptake, are forms of indirect calorimetry. It is measured using a respirometer. The respiratory quotient value indicates which macronutrients are being metabolized, as different energy pathways are used for fats, carbohydrates, and proteins. If metabolism consists solely of lipids, the respiratory quotient is approximately 0.7, for proteins it is approximately 0.8, and for carbohydrates it is 1.0. Most of the time, however, energy consumption is composed of both fats and carbohydrates. The approximate respiratory quotient of a mixed diet is 0.8. Some of the other factors that may affect the respiratory quotient are energy balance, circulating insulin, and insulin sensitivity.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
Synthesizing units (SUs) are generalized enzymes that follow the rules of classic enzyme kinetics with two modifications:
An V1-morph is an organism that changes in shape during growth such that its surface area is proportional to its volume. In most cases both volume and surface area are proportional to length
A V0-morph is an organism whose surface area remains constant as the organism grows.
Measures of pollutant concentration are used to determine risk assessment in public health.
The DEBtox method for the evaluation of effects of toxicants makes use of the Dynamic Energy Budget (DEB) theory to quantify the effect. See the Organisation for Economic Co-operation and Development (OECD) report, below, for a description of the method.
Soil respiration refers to the production of carbon dioxide when soil organisms respire. This includes respiration of plant roots, the rhizosphere, microbes and fauna.
The following outline is provided as an overview of and topical guide to cell biology:
Maintenance respiration refers to metabolism occurring in an organism that is needed to maintain that organism in a healthy, living state. Maintenance respiration contrasts with growth respiration, which is responsible for the synthesis of new structures in growth, nutrient uptake, nitrogen (N) reduction and phloem loading, whereas maintenance respiration is associated with protein and membrane turnover and maintenance of ion concentrations and gradients.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology, Glossary of environmental science and Glossary of scientific naming, or any of the organism-specific glossaries in Category:Glossaries of biology.
References
- 1 2 Kooijman, S. A. L. M. (2001). "Quantitative aspects of metabolic organization: a discussion of concepts". Philosophical Transactions of the Royal Society of London B: Biological Sciences. 356 (1407): 331–349. doi:10.1098/rstb.2000.0771. ISSN 0962-8436. PMC 1088431 . PMID 11316483.
- ↑ M., Kooijman, S. A. L. (1993). Dynamic energy budgets in biological systems : theory and applications in ecotoxicology. Cambridge: Cambridge University Press. ISBN 978-0521452236. OCLC 29596070.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ↑ Jusup, Marko; Sousa, Tânia; Domingos, Tiago; Labinac, Velimir; Marn, Nina; Wang, Zhen; Klanjšček, Tin (2017). "Physics of metabolic organization". Physics of Life Reviews. 20: 1–39. doi: 10.1016/j.plrev.2016.09.001 . PMID 27720138.
- ↑ Ledder, Glenn (2014). "The Basic Dynamic Energy Budget Model and Some Implications". Letters in Biomathematics. 1:2 (2): 221–233. doi: 10.1080/23737867.2014.11414482 .
- 1 2 3 Kooijman, S. A. L. M. (2010). Dynamic Energy Budget Theory for Metabolic Organisation. Cambridge University Press. ISBN 9780521131919.
- ↑ Zonneveld, C; Kooijman, S (1993). "Comparative kinetics of embryo development". Bulletin of Mathematical Biology. 55 (3): 609–635. doi:10.1016/s0092-8240(05)80242-3. PMID 8364420.