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Comprised of is an expression in English that means "composed of". [1] This is thought by language purists to be improper because to "comprise" (without the "of") can already mean to "be composed of". By that definition, "comprised of" would be ungrammatical as it implies "composed of of".
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound.
All of these contain many chemical bonds, but are not made of identifiable molecules. No typical molecule can be defined for salts nor for covalent crystals, although these are often composed of repeating unit cells that extend either in a plane, e.g. graphene; or three-dimensionally e.g. diamond, quartz, sodium chloride.
About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life.
On the scale of elementary particles, a definition that follows this tradition can be stated as: "ordinary matter is everything that is composed of quarks and leptons", or "ordinary matter is everything that is composed of any elementary fermions except antiquarks and antileptons".
The eukaryotic cytoskeleton is composed of microtubules, intermediate filaments and microfilaments. In the cytoskeleton of a neuron the intermediate filaments are known as neurofilaments . There are a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. [ 2 ]
Many proteins are composed of several protein domains, i.e. segments of a protein that fold into distinct structural units. [54]: 134 Domains usually have specific functions, such as enzymatic activities (e.g. kinase) or they serve as binding modules. [54]: 155–156 Protein domains vs. motifs.
Different forms of pure carbon, such as diamond, graphite, fullerenes and carbon nanotubes [4] are also excluded because they are simple substances composed of a single element and so not generally considered chemical compounds. The word "organic" in this context does not mean "natural". [5]