KBIT-2 key terms

The net movement of water molecules across a selectively permeable membrane from a region of higher water potential to one of lower water potential, driven by solute concentration differences.

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

The ability of an external solution to cause water to enter or leave a cell, classified as hypotonic, isotonic, or hypertonic relative to the cell's internal solute concentration.

The specific pocket or cleft on an enzyme's surface where substrate binds and catalysis occurs, shaped by the protein's three-dimensional folding and complementary to the substrate.

A form of enzyme inhibition in which a molecule resembling the substrate binds the active site, blocking substrate access; its effect can be reduced by raising substrate concentration.

Control of protein activity by a molecule binding at a site distinct from the active site, changing the protein's shape and thereby increasing or decreasing its function.

Loss of a protein's functional three-dimensional structure caused by heat, extreme pH, or chemical agents, disrupting hydrogen bonds and other interactions without breaking peptide bonds.

Adenosine triphosphate, the universal energy-carrying molecule of cells; hydrolysis of its terminal phosphate bond releases energy that powers endergonic cellular reactions and processes.

The anaerobic first stage of cellular respiration in which one glucose molecule is split and converted into two pyruvate molecules, yielding a net gain of two ATP and two NADH.

A series of reactions in the mitochondrial matrix that oxidizes acetyl-CoA, releasing carbon dioxide and generating NADH, FADH2, and a small amount of ATP.

ATP synthesis driven by the flow of protons down an electrochemical gradient through ATP synthase across a membrane, typically the inner mitochondrial membrane or thylakoid membrane.

One of two or more alternative versions of a gene at a given locus, which may differ in nucleotide sequence and produce different observable traits.

The particular combination of alleles an individual carries at one or more genetic loci, which together with environmental influence contributes to the observable phenotype.

The observable characteristics of an organism, resulting from the interaction between its genotype and environmental factors rather than from genes alone.

A relationship between alleles in which both are fully expressed in the heterozygote, so the phenotype shows both traits distinctly, as in human AB blood type.

A relationship in which the heterozygote shows a blended intermediate phenotype between the two homozygotes, because neither allele completely masks the other.

Genes located close together on the same chromosome that tend to be inherited together and do not assort independently, though crossing over can separate them.

The exchange of corresponding chromosome segments between homologous chromosomes during prophase I of meiosis, generating new combinations of alleles on a chromosome.

The proportion of offspring showing recombination between two loci, used as a measure of genetic distance and as evidence for the relative positions of genes on a chromosome.

The maintenance of a relatively stable internal environment within an organism despite external fluctuations, achieved through negative and positive feedback control systems.

A control mechanism in which a change in a variable triggers a response that opposes and reverses the change, restoring the variable toward its set point.

The physiological control of water and solute balance in body fluids, maintaining appropriate osmotic pressure through processes such as kidney filtration and hormone-regulated reabsorption.

A rapid, transient reversal of membrane potential along a neuron or muscle cell, produced by sequential ion channel opening and propagated as a nerve impulse.

A brief interval after an action potential during which a neuron cannot fire again, ensuring impulses travel in one direction and limiting maximum firing frequency.

The junction between two neurons or between a neuron and a target cell, across which a signal is transmitted chemically by neurotransmitters or electrically by gap junctions.

A chemical messenger released from a presynaptic terminal that diffuses across a synaptic cleft and binds receptors on a postsynaptic cell, altering its excitability.

The maximum population size of a species that a given environment can sustain indefinitely, determined by available resources, space, and other limiting factors.

An environmental resource or condition that is in shortest supply relative to demand and therefore restricts the growth, distribution, or abundance of a population.

A position in a food chain defined by the number of energy-transfer steps from the primary producer, such as primary consumer or secondary consumer.

A species whose influence on community structure is disproportionately large relative to its abundance, so its removal causes substantial changes to the ecosystem.

The differential survival and reproduction of individuals due to heritable variation in traits, causing advantageous alleles to increase in frequency across generations.

Random change in allele frequencies in a population across generations, especially strong in small populations, independent of any selective advantage.

The transfer of alleles between populations through migration of individuals or gametes, which tends to reduce genetic differences among populations.

The relative contribution an individual makes to the gene pool of the next generation, often measured as reproductive success compared with other phenotypes in the population.

The loss of water vapor from plant surfaces, mainly through stomata in leaves, which drives upward water movement in the xylem and cools the plant.

Vascular tissue that conducts water and dissolved minerals upward from roots to shoots, composed of dead, lignified cells such as tracheids and vessel elements.

Vascular tissue that transports sugars and other organic solutes from sources to sinks throughout the plant, using living sieve-tube elements supported by companion cells.

Small pores in the leaf epidermis, each bounded by two guard cells, that regulate gas exchange and water loss by opening and closing.

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

The movement of genetic material between organisms other than by parent-to-offspring inheritance, occurring in bacteria through transformation, transduction, and conjugation.

A small, circular, extrachromosomal DNA molecule that replicates independently of the bacterial chromosome and often carries genes such as those for antibiotic resistance.