NBE Sciences key terms

The net movement of water across a semipermeable membrane from a region of lower solute concentration to one of higher solute concentration, driven by a difference in water potential.

The passive net movement of particles from an area of higher concentration to an area of lower concentration, driven by random thermal motion until equilibrium is approached.

The ability of an external solution to cause water to move into or out of a cell, determined by the concentration of nonpenetrating solutes relative to the intracellular fluid.

A protein or RNA molecule that speeds up a biochemical reaction by lowering its activation energy, remaining unchanged itself and typically acting with high substrate specificity.

The specific region of an enzyme where substrate binds and catalysis occurs, whose shape and chemical environment determine substrate specificity and catalytic activity.

A form of enzyme inhibition in which an inhibitor resembling the substrate binds the active site, raising the substrate concentration needed for a given reaction rate while maximal velocity stays unchanged.

The process of nuclear division that produces two genetically identical daughter nuclei, typically followed by cytokinesis, maintaining chromosome number in somatic cells.

A two-stage reduction division producing four haploid gametes with recombined chromosomes, generating genetic variation through independent assortment and crossing over.

The reciprocal exchange of chromosome segments between homologous chromatids during prophase I of meiosis, creating new combinations of alleles on a chromosome.

The ordered sequence of growth, DNA replication, and division phases through which a cell passes, comprising interphase and the mitotic phase and controlled by checkpoints.

A concentration expression giving the number of moles of solute dissolved per liter of solution, abbreviated M and dependent on solution volume rather than solvent mass.

A concentration expression giving the number of moles of solute per kilogram of solvent, abbreviated m and independent of temperature because it uses mass rather than volume.

The amount of substance containing exactly 6.022 x 10^23 representative particles, the bridge between counted particles and measurable mass in stoichiometric calculations.

The quantitative relationship between amounts of reactants and products in a balanced chemical equation, used to calculate masses, moles, and volumes consumed or formed.

The reactant that is entirely consumed first in a reaction and therefore determines the maximum amount of product that can be formed.

A logarithmic scale expressing the negative base-10 logarithm of hydrogen ion activity in a solution, with values below 7 acidic and above 7 basic at standard conditions.

A solution of a weak acid and its conjugate base, or a weak base and its conjugate acid, that resists large changes in pH when small amounts of strong acid or base are added.

The negative base-10 logarithm of the acid dissociation constant, indicating the pH at which a weak acid is half dissociated and describing acid strength.

The minimum energy that colliding reactant molecules must possess for a reaction to proceed, lowered by catalysts such as enzymes without altering overall reaction thermodynamics.

The rule that a system at equilibrium subjected to a stress such as concentration, pressure, or temperature change shifts in the direction that partially offsets that stress.

A specific grouping of atoms within an organic molecule that gives the molecule characteristic chemical reactivity and physical properties regardless of the surrounding carbon skeleton.

One of two or more compounds sharing the same molecular formula but differing in the arrangement of atoms, which may be constitutional or stereochemical.

The geometric property of a molecule that is not superimposable on its mirror image, usually arising from a carbon bonded to four different groups.

One of a pair of stereoisomers that are non-superimposable mirror images of each other, often differing in biological activity and optical rotation direction.

An electron-rich species that donates an electron pair to an electron-deficient center, attacking electrophiles in substitution and addition reactions.

An electron-deficient species that accepts an electron pair from a nucleophile, acting as the target of attack in substitution, addition, and related reactions.

The principle that the net force acting on an object equals its mass multiplied by its acceleration, relating force, mass, and resulting motion.

The energy transferred to or from an object when a force acts through a displacement, calculated as the product of force and displacement along the force direction.

The energy an object possesses because of its motion, equal to one half the mass times the square of its speed.

A vector quantity equal to the product of an object's mass and velocity, conserved in a closed system when no external net force acts.

The relationship stating that current through a conductor equals the voltage across it divided by its resistance, valid for ohmic materials at constant temperature.

A bone-forming cell of mesenchymal origin that secretes and mineralizes osteoid, becoming embedded as an osteocyte once surrounded by matrix.

A large multinucleated cell derived from hematopoietic precursors that resorbs bone matrix by secreting acid and enzymes, central to bone remodeling.

The cylindrical structural unit of compact bone consisting of concentric lamellae surrounding a central canal that carries blood vessels and nerves.

The repeating contractile unit of striated muscle between two Z lines, containing overlapping actin and myosin filaments whose sliding shortens the muscle.

The explanation of muscle contraction in which myosin heads bind actin and cycle through power strokes, pulling thin filaments toward the sarcomere center and shortening it.

A rapid, self-propagating change in membrane voltage caused by sequential ion channel openings, used for signaling in neurons and muscle fibers.

The steady electrical difference across a cell membrane at rest, typically about minus 70 millivolts in neurons, set mainly by potassium permeability and the sodium-potassium pump.

The volume of plasma filtered by the renal glomeruli per unit time, reflecting filtration pressure, surface area, and permeability, and used to assess kidney function.

A vascular and cellular response to injury or infection marked by redness, heat, swelling, pain, and often loss of function, aimed at removing the cause and repairing tissue.

Pathological cell death resulting from severe injury, characterized by cell swelling, membrane rupture, leakage of contents, and an associated inflammatory response.

Programmed cell death executed by regulated intracellular enzymes, producing cell shrinkage and membrane-bound fragments cleared without provoking inflammation.

The abnormal, autonomous proliferation of cells that persists after the initiating stimulus is removed, forming a mass that may be benign or malignant.

The spread of malignant cells from a primary tumor to distant sites through lymphatics, blood vessels, or body cavities, where secondary tumors grow.

The continuous coupled process in which osteoclasts resorb old bone and osteoblasts deposit new bone, maintaining skeletal strength and mineral homeostasis.

A differential staining method that divides bacteria into gram-positive and gram-negative groups based on cell wall structure and retention of crystal violet dye.

The cross-linked polymer of sugars and short peptides forming the bacterial cell wall, thicker in gram-positive organisms and the target of penicillin antibiotics.

The ability of bacteria to survive and grow in the presence of an antibiotic that would normally inhibit or kill them, acquired by mutation or gene transfer.

A structured community of microorganisms attached to a surface and embedded in a self-produced matrix, often showing reduced susceptibility to antimicrobial agents.

The reduction in volume of a resin-based dental material as monomer molecules join into polymer chains, which can create stress at the restoration-tooth interface.

A material property quantifying how much a material expands per unit length for each degree of temperature rise, relevant to marginal adaptation of restorations.

Accelerated corrosion caused by electrical contact between dissimilar metals in an electrolyte such as saliva, producing currents and possible discomfort.

The ratio of stress to strain within the elastic region of a material's stress-strain curve, indicating its stiffness or resistance to elastic deformation.