Glossary of Scientific Terms

M

Macromolecules
Large molecules in biological systems namely proteins, nucleic acids, and polysaccharides.

Macro-Nutrients
Also called caloric nutrients including proteins, carbohydrates, and fats. Some definitions include water and alcohol. The term is used by gardeners and in agriculture referring to common minerals needed for proper plant growth.

Macroscopic
Used in science to describe large scale processes like the temperature, volume, pressure,and energy of a system characterizing the behavior of a very large number of molecules. The macroscopic values tend to be predictable and represent the average behavior of a system. They give no detailed information about the behavior of individual molecules or units of a system.

Microarray
A microarray is an experimental platform used to study the presence or activity of a full set of genes or proteins found in a cell or organism. When studying the presence of genes, the microarray (DNA microarray) is used for genotyping, i.e., assessing the full genetic complement of an organism as compared to a closely related organism.

Micro-Nutrients
Vitamins or Minerals that are needed in daily amounts up to a few milligrams.

Microscopic
The description of the behavior of individual molecules (at the molecular level). The behavior of an individual molecule may be very different from other identical molecules. In systems with a very large number of identical molecules, these individual deviations are negligible and contribute to the noise (random fluctuation) of a property of this system. The decay of a radioactive material is a good example of such an internal fluctuation. While the decay of isotopes can be predicted for a large clump of radioactive material (e.g. its half-life time, which is a macroscopic property), the actual time point of decay of an individual isotope cannot be predicted with accuracy and is random. However, we can assign a probability that it will decay within a certain amount of time (similar arguments can be made for individuals who have risk factors indicating the chance of developing a disease like cancer or a heart attack).

Membrane (cell membrane; phospholipid bilayer)
A planar structure surrounding cells and organelles within eukaryotic cells (e.g. membranes of cell nucleus of mitochondrion) separating aqueous compartments which carry out different metabolic processes. Cell membranes are electrical insulators but permeable to hydrophobic molecules such as steroidal hormones and small gases (carbon dioxide, molecular oxygen, nitric oxide). All other water soluble and charged molecules depend on the presence of membrane proteins which provide transport pathways across the phospholipid bilayer.

Metabolism, metabolic
The totality of all chemical processes in cells and all living organisms. Metabolism is the chemistry of energy extraction from nutrients and the biosynthesis of the building blocks of life (amino acids, sugars, lipids). A process by which absorbed nutrients are converted to chemical energy and building blocks for vital processes or cellular structures. Metabolism regulates the rate at which you burn Calories.

Microflora
The bacterial colonies found in the large intestine. These bacteria are important for proper digestion and fecal excretion of waste products.

Molecular Biology
The science of studying the genetic composition and mechanism of living organisms at the molecular level. It historically refers to the understanding and manipulation of genes (DNA). The molecular studies of all other organic molecules like proteins, fats, and carbohydrates is called biochemistry.

Molecule
A chemically unique aggregate of at least two atoms (see also elements).  The atoms are linked to each other by chemical (covalent) bonds. All matter is made up of molecules. Free atoms are rarely found but are important in the form of salts or metal ions in water.

Mutation, mutant
Mutations are changes in the nucleotide sequence of the genome (affecting genes) and the resulting changes in the amino acid sequence of proteins. The amino acid sequence of proteins determines their structure and function, the latter being subject to natural selection. Mutation occur in different forms, from single nucleotide mutations to insertions and deletions of longer sequences as well as gene duplications, deletions and chromosomal rearrangements in higher organisms.