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[4] [5] Plate tectonics are needed for life over a long time span, and carbon-based life is important in the plate tectonics process. [6] Iron- and sulfur-based Anoxygenic photosynthesis life forms that lived from 3.80 to 3.85 billion years ago on Earth produced an abundance of black shale deposits. These shale deposits increase heat flow and ...
Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. [1] A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, and metabolism.
A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1]
NASA defines life as "a self-sustaining chemical system capable of Darwinian [i.e., biological] evolution." [4] Such a system is complex; the last universal common ancestor (LUCA), presumably a single-celled organism which lived some 4 billion years ago, already had hundreds of genes encoded in the DNA genetic code that is universal today.
Organic compounds form the basis of all earthly life and constitute the majority of known chemicals. The bonding patterns of carbon, with its valence of four—formal single, double, and triple bonds, plus structures with delocalized electrons —make the array of organic compounds structurally diverse, and their range of applications enormous.
The possibility of life-forms being based on "alternative" biochemistries is the topic of an ongoing scientific discussion, informed by what is known about extraterrestrial environments and about the chemical behaviour of various elements and compounds. It is of interest in synthetic biology and is also a common subject in science fiction.
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis, organisation, metabolism, growth, adaptation, response to stimuli, and reproduction.
The uniformity of both specific types of molecules (the biomolecules) and of certain metabolic pathways are invariant features among the wide diversity of life forms; thus these biomolecules and metabolic pathways are referred to as "biochemical universals" [4] or "theory of material unity of the living beings", a unifying concept in biology ...