BIO - TERMS - MOLECUL Flashcards
Absorption spectrum
A plot of wavelength of incident light versus amount of light absorbed. Organic molecules show absorption spectra in both the infrared and the ultraviolet regions of the electromagnetic spectrum.
Achiral
Having a lack of handedness. A molecule is achiral if it has a plane of symmetry and is thus superimposable on its mirror image.
activated carrier
Small diffusible molecule that stores easily exchangeable energy in the form of one or more energy-rich covalent bonds. Examples are ATP, acetyl CoA, FADH2, NADH, and NADPH.
alloreactivity
The recognition by T cells of MHC molecules other than self. Such responses are also called alloreactions or alloreactive responses.
amorphous
A term describing a solid in which atoms or molecules do not have any long-range order.
Amorphous ice/vitrified ice
Form of solidified water in which molecules are randomly arranged in a glass-like solid state; this is in contrast to crystalline ice where molecules are regularly arranged in a lattice needing more space.
anaerobic respiration
Respiration in which the final electron acceptor in the electron transport chain is an inorganic molecule other than molecular oxygen (O2); for example, a nitrate ion or CO2.
analyte
A molecule to be analyzed by mass spectrometry.
Angle strain
The strain introduced into a molecule when a bond angle is deformed from its ideal value. Angle strain is particularly important in small-ring cyclo alkanes, where it results from compression of bond angles to less than their ideal tetrahedral values.
Annulation
The building of a new ring onto an existing molecule.
anoxygenic
Not producing molecular oxygen; typical of cyclic photophosphorylation.
Antiaromatic
Referring to a planar, conjugated molecule with 4n π electrons. Delocalization of the p electrons leads to an increase in energy.
aptamer
Oligonucleotide that binds specifically to one molecular target, usually selected by an iterative cycle of affinity-based enrichment (SELEX).
Aromaticity
The special characteristics of cyclic conjugated molecules, including unusual stability and a tendency to undergo substitution reactions rather than addition reactions on treatment with electrophiles. Aromatic molecules are planar, cyclic, conjugated species with 4n + 2 π electrons.
asymmetric cell division
Cell division in which some important molecule or molecules are distributed unequally between the two daughter cells, causing these cells to become different from each other.
ball-and-stick molecular model
A model that represents atoms as balls and chemical bonds as sticks; how the two connect reflects a molecule’s shape.
band theory
A model for bonding in atomic solids based on molecular orbital theory in which atomic orbitals combine and become delocalized over the entire crystal.
bent geometry
A molecular geometry in which the angle between three bonded atoms is approximately 109° (but could be less).
bond order
For a molecule, the number of electrons in bonding orbitals minus the number of electrons in nonbonding orbitals divided by two; a positive bond order implies that the molecule is stable.
Bridgehead
An atom that is shared by more than one ring in a polycyclic molecule.
Carboxylation
The addition of CO2 to a molecule.
catenane
Two or more circular polymeric molecules interlinked by one or more noncovalent topological links, resembling the links of a chain.
Cation radical
A reactive species, typically formed in a mass spectrometer by loss of an electron from a neutral molecule and having both a positive charge and an odd number of electrons.
cellulose microfibril
Highly ordered crystalline aggregate formed from bundles of about 40 cellulose chains, arranged with the same polarity and stuck together in overlapping parallel arrays by hydrogen bonds between adjacent cellulose molecules.
Chair conformation
A three-dimensional conformation of cyclohexane that resembles the rough shape of a chair. The chair form of cyclohexane is the lowest-energy conformation of the molecule.
Chelators
Small molecules that bind a metal with high affinity.
chemical biology
Name given to a strategy that uses largescale screening of hundreds of thousands of small molecules in biological assays to identify chemicals that affect a particular biological process and that can then be used to study it.
chemoattractant
A diffusible molecule that acts over a distance to attract growing axons.
chemorepellent
A diffusible molecule that acts over a distance to repel growing axons.
Chiral environment
The chiral surroundings or conditions in which a molecule resides.
Chromophore-binding domain
Part of a photoreceptor molecule that binds the chromophore; absorbs light and triggers activity of the output-domain that links photoreceptor activity to downstream signaling.
CIIV
An early endocytic compartment containing MHC class II molecules in dendritic cells.
collision model
A model of chemical reactions in which a reaction occurs after a sufficiently energetic collision between two reactant molecules.
column chromatography
Technique for separation of a mixture of substances in solution by passage through a column containing a porous solid matrix. Substances are retarded to different extents by their interaction with the matrix and can be collected separately from the column. Depending on the matrix, separation can be according to charge, hydrophobicity, size, or the ability to bind to other molecules.
Compatible solutes
Small molecules involved in the osmoregulation of the cell (osmoprotectants, osmolytes).
conduction band
In band theory, the band of energy levels that forms from antibonding molecular orbitals.
Conformational analysis
A means of assessing the energy of a substituted cycloalkane by totaling the steric interactions present in the molecule.
Conjugation reactions
Reactions in which a hydrophilic molecule becomes covalently linked to a chemical.
contact-dependent signaling
Form of intercellular signaling in which signal molecules remain bound to the surface of the signaling cell and influence only cells that contact it.
contour length
The length of a helical polymeric molecule as measured along its helical axis.
crystalline
A term that describes a solid in which atoms, molecules, or ions are arranged in patterns with long-range, repeating order.
decomposition reaction
A chemical reaction in which bonds are broken to produce smaller parts from a large molecule.
Degree of unsaturation
The number of rings and/or multiple bonds in a molecule.
dehydration synthesis
Chemical reaction in which water is formed during formation of a complex molecule.
Dieckmann cyclization reaction
An intra molecular Claisen condensation reaction of a diester to give a cyclic b-keto ester.
dimerization
An event in which two molecular complexes interact and proceed to perform a purposeful function.
doubly labeled water (DLW)
Tool used to assess energy expenditure based on estimations of CO2 production; uses water molecules with isotopes of hydrogen ²H and ¹⁸O.
Eclipsing strain
The strain energy in a molecule caused by electron repulsions between eclipsed bonds. Eclipsing strain is also called torsional strain.
Electron-dot structure
A representation of a molecule showing valence electrons as dots.
Electrostatic potential maps
Molecular representations that use color to indicate the charge distribution in molecules as derived from quantum-mechanical calculations.
Entropy change (DS)
The change in amount of molecular randomness. The entropy change that occurs during a reaction is a measure of the difference in randomness between reactants and products.
ESI
Electrospray ionization; a “soft” ionization method used for mass spectrometry of biological samples of very high molecular weight.
ethylene
Small gas molecule that is a plant growth regulator influencing plant development in various ways including promoting fruit ripening, leaf abscission, and plant senescence and functioning as a stress signal in response to wounding, infection, and flooding.
excited state
An energy-rich state of an atom or molecule, produced by the absorption of light energy; as distinct from ground state.
Fischer projections
A means of depicting the absolute coniguration of a chiral molecule on a lat page. A