A macromolecule is a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. [1] The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ...

A macromolecule is a molecule composed of a very large number of atoms. But generally the use of term is restricted to molecules of more than 100 atoms, and in particular to polymers. Many examples come from biology and in particular biochemistry. These include proteins, starches, lipids and nucleic acids (such as DNA), which are sometimes called "biomacromolecules" or biopolymers. Synthetic examples include plastics. The integral domains of crystals and metals, while composed of very large numbers of atoms joined by molecule-like bonds, are rarely referred to as "macromolecules." A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Properties For alternative meanings see atom (disambiguation). ... A polymer is a generic term used to describe a substantially long molecule. ... Biochemistry is the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... Figure 1: Structure of a Lipid. ... Highly simplified diagram of a double-stranded nucleic acid. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... A biopolymer is a polymer found in nature. ... Plastic is a term that covers a range of synthetic or semisynthetic polymerization products. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Metal - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...

The term "macromolecule" is sometimes used to refer to aggregates of two or more macromolecules held together by intermolecular forces rather than by chemical bonds. This usage is common in particular when the individual macromolecules involved aggregate or "assemble" spontaneously and rarely exist in isolation. Such an aggregate is more properly called a macromolecular complex. In such a context, individual macromolecules are often referred to as subunits (see e.g. protein subunit). Intermolecular forces are electromagnetic forces which act between molecules or between widely separated regions of a macromolecule. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... In structural biology, a protein subunit or subunit protein is a single protein molecule that assembles (or coassembles) with other protein molecules to form a multimeric or oligomeric protein. ...

Substances that are composed of macromolecules often have unusual physical properties. The properties of liquid crystals and such elastomers as rubber are examples. Although too small to see, individual pieces of DNA in solution can be broken in two simply by suctioning the solution through an ordinary straw. This is not true of smaller molecules. The 1964 edition of Linus Pauling's College Chemistry asserted that DNA in nature is never longer than about 5000 base pairs. This is because biochemists were inadvertently and with perfect consistency breaking their samples into pieces. In fact, the DNA of chromosomes can be tens of millions of base pairs long. Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... The term elastomer is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. ... Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. ... Linus Carl Pauling (February 28, 1901 – August 19, 1994) was an American physical chemist, widely regarded as the premier chemist of the twentieth century. ... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... Figure 1: Chromosome. ...

Another common macromolecular property that does not characterize smaller molecules is the need for assistance in dissolving into solution. Many require salts or particular ions to dissolve in water. Proteins will denature if the solute concentration of their solution is too high or too low. In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. ... An ion is an atom or group of atoms with a net electric charge. ... Cheese In biochemistry, denaturation is a structural change in biomolecules such as nucleic acids and proteins, such that they are no longer in their native state (the shape which allows for optimal biological activity). ...

According to IUPAC recommendations the term macromolecule is reserved for an individual molecule and the term polymer is used as to denote a substance composed of macromolecules. Polymer may also be employed unambiguously as an adjective, according to accepted usage, e.g. polymer blend, polymer molecule. [2] The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ... A polymer is a generic term used to describe a substantially long molecule. ...

LINKS

http://www.mansfield.ohio-state.edu/~sabedon/campbl05.htm http://www.langara.bc.ca/biology/mario/Biol1115notes/biol1115chap5.html