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  2. Matter - Wikipedia

    en.wikipedia.org/wiki/Matter

    A definition of "matter" based on its physical and chemical structure is: matter is made up of atoms. [17] Such atomic matter is also sometimes termed ordinary matter. As an example, deoxyribonucleic acid molecules (DNA) are matter under this definition because they are made of atoms.

  3. Biological roles of the elements - Wikipedia

    en.wikipedia.org/wiki/Biological_roles_of_the...

    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]

  4. Characteristic property - Wikipedia

    en.wikipedia.org/wiki/Characteristic_property

    A characteristic property is a chemical or physical property that helps identify and classify substances. The characteristic properties of a substance are always the same whether the sample being observed is large or small. Thus, conversely, if the property of a substance changes as the sample size changes, that property is not a characteristic ...

  5. Cell (biology) - Wikipedia

    en.wikipedia.org/wiki/Cell_(biology)

    The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: the presence of membrane-bound organelles (compartments) in which specific activities take place. Most important among these is a cell nucleus, [2] an organelle that houses the cell's DNA. This nucleus gives the eukaryote its name, which means ...

  6. Intrinsic and extrinsic properties - Wikipedia

    en.wikipedia.org/wiki/Intrinsic_and_extrinsic...

    [2] In biology, intrinsic effects originate from inside an organism or cell, such as an autoimmune disease or intrinsic immunity. In electronics and optics, intrinsic properties of men (or systems of devices) are generally those that are free from the corn field of various types of non-essential defects. [3]

  7. Properties of water - Wikipedia

    en.wikipedia.org/wiki/Properties_of_water

    2 O in far lower amounts (0.000003%) and any such molecules are temporary as the atoms recombine. The most notable physical differences between H 2 O and D 2 O, other than the simple difference in specific mass, involve properties that are affected by hydrogen bonding, such as freezing and boiling, and other kinetic effects. This is because the ...

  8. Chemistry - Wikipedia

    en.wikipedia.org/wiki/Chemistry

    Chemistry is the scientific study of the properties and behavior of matter. [1] It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances.

  9. Biochemistry - Wikipedia

    en.wikipedia.org/wiki/Biochemistry

    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.