BIO - TERMS - ELECTR Flashcards
1,4-Addition
Addition of a reactant to the ends of a conjugated π system. Conjugated dienes yield 1,4 adducts when treated with electrophiles such as HCl. Conjugated enones yield 1,4 adducts when treated with nucleophiles such as amines.
ampere (A)
The SI unit for electrical current; 1 A = 1 C/s.
Antarafacial
A pericyclic reaction that takes place on opposite faces of the two ends of a p electron system.
Antimycin A
An inhibitor of electron flow through the QH2-cytochrome c reductase complex.
bidentate
A term describing ligands that donate two electron pairs to the central metal.
bioelectrical impedance analysis (BIA)
Procedure for assessing body composition in which an electric current is passed through the body. The resistance to current flow reflects the relative amount of fat present.
cathode
The electrode in an electrochemical cell at which reduction occurs; electrons flow toward the cathode.
cathode ray
A stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube.
cathode ray tube
An evacuated tube containing charged plates to accelerate and view electron beams.
cell potential (cell emf) (Ecell)
The potential difference between the cathode and the anode in an electrochemical cell.
complementary properties
Properties that exclude one another; that is, the more you know about one, the less you know about the other. For example, the wave nature and particle nature of the electron are complementary.
Conrotatory
A term used to indicate that p orbitals must rotate in the same direction during electrocyclic ringopening or ring-closure.
coordinate covalent bond
The bond formed when a ligand donates electrons to an empty orbital of a metal in a complex ion.
core electrons
Those electrons in a complete principal energy level and those in complete d and f sublevels.
cyclic electron flow
In chloroplasts, the light-induced flow of electrons originating from and returning to photosystem I.
cytochrome c
Soluble component of the mitochondrial electron-transport chain. Its release into the cytosol from the mitochondrial intermembrane space also initiates apoptosis.
cytochrome c reductase
Second of the three electrondriven proton pumps in the respiratory chain. Accepts electrons from ubiquinone and passes them to cytochrome c.
Deactivating groups
Electron-withdrawing substituents that decrease the reactivity of an aromatic ring toward electrophilic aromatic substitution.
degenerate
A term describing two or more electron orbitals with the same value of n that have the same energy.
Deshielding
An effect observed in NMR that causes a nucleus to absorb toward the left (downield) side of the chart. Deshielding is caused by a withdrawal of electron density from the nucleus.
diode
A device that allows the flow of electrical current in only one direction.
Disrotatory
A term used to indicate that p orbitals rotate in opposite directions during electro cyclic ring-opening or ring-closing reactions.
duet
A Lewis symbol with two dots, signifying a filled outer electron shell for the elements H and He.
effective nuclear charge (Zeff)
The actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electrons.
electrical charge
A fundamental property of certain particles that causes them to experience a force in the presence of electric fields.
electrical conductance
The relative ability of an electrical charge to migrate from one point to another, represented by the symbol g and measured in siemens (S). Conductance is the inverse of resistance and is related to electrical current and voltage by Ohm’s law.
electrical potential
The force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called voltage or potential difference.
electrical resistance
The relative inability of an electrical charge to migrate from one point to another, represented by the symbol R and measured in ohms (Ω). Resistance is the inverse of conductance and is related to electrical current and voltage by Ohm’s law.
electrical self-stimulation
Electrical stimulation that an animal can voluntarily deliver to a portion of its brain.
electroconvulsive therapy (ECT)
A treatment for major depression that involves eliciting electrical seizure activity in the brain.
Electrocyclic reaction
A unimolecular pericyclic reaction in which a ring is formed or broken by a concerted reorganization of electrons through a cyclic tran sition state. For example, the cyclization of 1,3,5-hexatriene to yield 1,3-cyclohexadiene is an electrocyclic reaction.
electrode
A conductive surface through which electrons can enter or leave a half-cell in an electrochemical cell.
electrolysis
The process in which electrical current drives an otherwise nonspontaneous redox reaction.
electrolyte balance
Maintenance of the appropriate levels of electrolytes (such as sodium ions) in body fluids.
electrolytic cell
An electrochemical cell that consumes electrical current to drive a nonspontaneous chemical reaction.
electromagnetic radiation
A form of energy embodied in oscillating electric and magnetic fields.
electromotive force (emf)
The force that results in the motion of electrons due to a difference in potential.
electron capture
The form of radioactive decay that occurs when a nucleus assimilates an electron from an inner orbital.
electron microscope (EM) tomography
Technique for viewing three-dimensional specimens in the electron microscope in which multiple views are taken from different directions by tilting the specimen holder. The views are combined computationally to give a three-dimensional image.
electron transfer
Movement of electrons from electron donor to electron acceptor; especially, from substrates to oxygen via the carriers of the respiratory (electron-transfer) chain.
Electrophilic aromatic substitution reaction
A reaction in which an electrophile (E1) reacts with an aromatic ring and substitutes for one of the ring hydrogens.
Friedel–Crafts reaction
An electro philic aromatic substitution reaction to alkylate or acylate an aromatic ring.
Glycerol phosphate shuttle
The transfer of electrons from cytoplasmic NADH to the respiratory chain.
Heterolytic bond breakage
The kind of bondbreaking that occurs in polar reactions when one fragment leaves with both of the bonding electrons: A:B → A+ + B:-.
high-spin complex
A complex ion with weak field ligands that have the same number of unpaired electrons as the free metal ion.
Homolytic bond breakage
The kind of bondbreaking that occurs in radical reactions when each fragment leaves with one bonding electron: A:B → A∙ + B∙.
Inductive efect
The electron-attracting or electron-withdrawing effect transmitted through s bonds.Electronegative elements have an electron-withdrawing inductive effect.
infrared (IR) radiation
Electromagnetic radiation emitted from warm objects, with wavelengths slightly larger than those of visible light.
inner hair cell
An auditory cell located between the modiolus and the rods of Corti; the primary transducer of sound into an electrochemical signal.
intercalated disc
(in-ter′kă-lā-ted disk) Intercellular junction between cardiac muscle cells composed of desmosomes and gap junctions that mechanically and electrically link these cells.
internal resistance
The resistance to electrical current flows longitudinally down a cable or neurite, represented by the symbol rᵢ.
Ion trap (IT)MS
Mass analyzer in mass spectrometry separating ions by trapping them in an electrodynamic field (ion trap) and ejecting them subsequently to the detector.
ionic equilibrium potential
The electrical potential difference that exactly balances an ionic concentration gradient, represented by the symbol E ion ; also known as equilibrium potential. IP₃ See inositol-1,4,5-triphosphate.
isoelectric focusing
An electrophoretic method for separating macromolecules on the basis of isoelectric pH.
kilowatt-hour (kWh)
An energy unit used primarily to express large amounts of energy produced by the flow of electricity; equal to 3.60 x 10⁶ J.
lithium ion battery
A battery that produces electrical current in the form of motion of lithium ions from the anode to the cathode.
Lone-pair electrons
Nonbonding valence-shell electron pairs. Lone-pair electrons are used by nucleophiles in their reactions with electrophiles.
low-spin complex
A complex ion with strong-field ligands that have fewer unpaired electrons than the free metal ion.
metabolic water
Water formed during dehydration reactions and during electron transport in aerobic cellular respiration; contributes approximately 8% of total fluid intake.
monodentate
A term that describes ligands that donate only one electron pair to the central metal.
n-type semiconductor
A semiconductor that employs negatively charged electrons in the conduction band as the charge carriers.
NADH dehydrogenase complex
First of the three electrondriven proton pumps in the mitochondrial respiratory chain, also known as Complex I. It accepts electrons from NADH and passes them to a quinone.
NADP+/NADPH (nicotinamide adenine dinucleotide phosphate/reduced nicotinamide adenine dinucleotide phosphate)
Electron carrier system closely related to NAD+/ NADH, but used almost exclusively in reductive biosynthetic, rather than catabolic, pathways.
noncyclic electron flow
The light-induced flow of electrons from water to NADP in oxygen-evolving photosynthesis; involves both photosystems I and II.
noncyclic photophosphorylation
The movement of an electron from chlorophyll to NAD+; plant and cyanobacterial photophosphorylation.
Octahedral complexes
Chemical complexes composed of a central transition metal cation and six ligands that bind to this metal by donating free electron pairs.The ligands are evenly spaced and form an octaeder.
Ohm’s law
The relationship between electrical current (I), voltage (V), and conductance (g): I gV. Because electrical conductance is the inverse of resistance (R), Ohm’s law may also be written: V = IR.
Orbitrap MS
Mass analyzer in mass spectrometry where the mass-to-charge ratio of ions is determined by the measurement of the frequency of the periodic ion movement in an electrostatic field.
p–n junctions
Tiny areas in electronic circuits that have p-type semiconductors on one side and n-type on the other.
Pericyclic reaction
A reaction that occurs in a single step by a reorganization of bonding electrons in a cyclic transition state.
photoelectric effect
The observation that many metals emit electrons when light falls upon them.
photoreduction
The light-induced reduction of an electron acceptor in photosynthetic cells.
pi-cation interactions
Chemical interaction between a cation (e.g., Na+) and the pi-electron system of an aromatic moiety.
Plane-polarized light
Light that has its electromagnetic waves oscillating in a single plane rather than in random planes. The plane of polarization is rotated when the light is passed through a solution of a chiral substance.
Polar reactions
Reactions in which bonds are made when a nucleophile donates two electrons to an electrophile and in which bonds are broken when one fragment leaves with both electrons from the bond.
polydentate
A term that describes ligands that donate more than one electron pair to the central metal.
positron
The particle released in positron emission; equal in mass to an electron but opposite in charge.
principal quantum number (n)
An integer that specifies the overall size and energy of an orbital. The higher the quantum number n, the greater the average distance between the electron and the nucleus and the higher its energy.
probability density
The probability (per unit volume) of finding the electron at a point in space as expressed by a three-dimensional plot of the wave function squared (ψ²).
quantum-mechanical model
A model that explains the behavior of absolutely small particles such as electrons and photons.
radial distribution function
A mathematical function (corresponding to a specific orbital) that represents the total probability of finding an electron within a thin spherical shell at a distance r from the nucleus.
Radical reactions
Reactions in which bonds are made by donation of one electron from each of two reactants and in which bonds are broken when each fragment leaves with one electron.
radio waves
The form of electromagnetic radiation with the longest wavelengths and smallest energy.
Reduction potential
A measure for the tendency of a redox couple to donate electrons in a redox reaction.
Resonance efect
The donation or withdrawal of electrons through orbital overlap with neighboring p bonds. For example, an oxygen or nitrogen substituent donates electrons to an aromatic ring by overlap of the O or N orbital with the aromatic ring p orbitals.
resting metabolic rate (RMR)
Level of energy expenditure during nonactive rest at a comfortable environmental temperature and 4 hours after the consumption of a meal; tends to be about 10% greater than basal metabolic rate. resting potential The resting electric charge of an excitable cell.
Ring-current
The circulation of p electrons induced in aromatic rings by an external magnetic ield. This effect accounts for the downield shift of aromatic ring protons in the 1H NMR spectrum.
Rotenone
A fish poison that inhibits electron flow through NADH-Q reductase.
SA nodal cells
Specialized cardiac muscle cells that serve as the heart’s pacemaker; spontaneously depolarize to initiate an electrical signal to cause the heart to contract.
Sector field (SF)MS
Mass analyzer in mass spectrometry with magnetic and electrostatic sectors that use the different dispersion of ions in magnetic or electric fields.
semiconductor
A material with intermediate electrical conductivity that can be changed and controlled.
spin quantum number (ms)
The fourth quantum number, which denotes the electron’s spin as either ½ (up arrow) or -½ (down arrow).
standard electrode potential
The potential of a half-cell in an electrochemical cell.
standard hydrogen electrode (SHE)
The half-cell consisting of an inert platinum electrode immersed in 1 M HCl with hydrogen gas at 1 atm bubbling through the solution; used as the standard of a cell potential of zero.
Suprafacial
A word used to describe the geometry of pericyclic reactions. Suprafacial reactions take place on the same side of the two ends of a p electron system.
synaptic signaling
Intercellular signaling performed by neurons that transmit signals electrically along their axons and release neurotransmitters at synapses, which are often located far away from the neuronal cell body.
transmission electron microscope (TEM)
An electron microscope that provides high magnifications (10,000–100,000*) of thin sections of a specimen.
uncoupling agent
A substance that uncouples phosphorylation of ADP from electron transfer; for example, 2,4-dinitrophenol.
visible light
Those frequencies of electromagnetic radiation that can be detected by the human eye.
voltaic (galvanic) cell
An electrochemical cell that produces electrical current from a spontaneous chemical reaction.
Water-water cycle
Metabolic pathway that dissipates excitation energy in photosynthesis by transferring electrons derived from water splitting in the oxygen-evolving complex on oxygen to produce superoxide, which is subsequently converted to hydrogen peroxide and finally water. This pathway either uses ascorbate and ascorbate peroxidase in the ascorbate-dependent water-water cycle or thiol reductases and peroxiredoxins in the thiol peroxidase-dependent water-water cycle.
weak electrolyte
A substance that does not completely ionize in water and only weakly conducts electricity in solution.
X-ray
Electromagnetic radiation with wavelengths slightly longer than those of gamma rays; used to image bones and internal organs.
Z scheme
The path of electrons in oxygenic photosynthesis from water through photosystem II and the cytochrome b6 f complex to photosystem I and finally to NADPH. When the sequence of electron carriers is plotted against their reduction potentials, the path of electrons looks like a sideways Z.
