MTTC Biology (017) flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Emergent properties

Characteristics that arise at higher levels of biological organization and cannot be predicted from the individual parts alone, such as life emerging from the interaction of molecules and organelles.

Dehydration synthesis

A reaction that joins two monomers by removing a water molecule, forming covalent bonds such as the peptide bond between amino acids or the glycosidic bond between sugars.

Hydrolysis

A reaction that breaks a covalent bond between monomers by adding water, splitting polymers such as starch, proteins, or nucleic acids into their subunits during digestion.

Endosymbiotic theory

The explanation that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by a host cell, supported by their own circular DNA, ribosomes, and double membranes.

Surface-area-to-volume ratio

The ratio of a cell's membrane area to its internal volume; it decreases as cells enlarge, limiting diffusion efficiency and constraining maximum cell size.

Enzyme active site

The specific region of an enzyme where substrate binds, lowering activation energy; its shape determines substrate specificity and can be altered by heat or extreme pH.

Competitive inhibitor

A molecule that resembles the substrate and binds the enzyme's active site, blocking substrate entry; its effect can be reduced by increasing substrate concentration.

Semiconservative replication

The process by which each new DNA molecule contains one original parental strand and one newly synthesized complementary strand, confirmed by the Meselson-Stahl experiment.

Transcription

RNA polymerase reads the DNA template strand and builds a complementary mRNA molecule using uracil instead of thymine, beginning at a promoter and ending at a terminator.

Translation

The process at the ribosome in which mRNA codons are matched to tRNA anticodons, delivering amino acids that are joined into a polypeptide chain.

Frameshift mutation

An insertion or deletion of nucleotides not in multiples of three, shifting the reading frame and altering every downstream codon, usually producing a nonfunctional protein.

Testcross

A cross between an individual of unknown genotype showing the dominant phenotype and a homozygous recessive individual, revealing the unknown genotype by the offspring ratios produced.

Incomplete dominance

A pattern in which the heterozygote shows an intermediate phenotype between the two homozygotes, as when red and white flowers produce pink offspring.

Hardy-Weinberg equilibrium

A model in which allele and genotype frequencies stay constant across generations when there is no mutation, migration, selection, or genetic drift and mating is random.

Gel electrophoresis

A technique that separates DNA fragments by size using an electric field; smaller, more negatively charged fragments migrate farther through the gel toward the positive electrode.

Polymerase chain reaction

A method that amplifies DNA through repeated cycles of denaturation, primer annealing, and extension by a heat-stable DNA polymerase, doubling the target sequence each cycle.

Natural selection

The process by which individuals with heritable traits that improve survival and reproduction in a given environment leave more offspring, changing allele frequencies in the population.

Homologous structures

Body parts in different species that share a common evolutionary origin and similar underlying anatomy, though they may differ in function, such as the forelimbs of mammals.

Genetic drift

A random change in allele frequencies due to chance events, most pronounced in small populations; bottleneck and founder effects are examples.

Reproductive isolation

Any barrier preventing members of different populations from interbreeding and producing fertile offspring, allowing them to diverge into separate species.

Binomial nomenclature

The two-part naming system created by Linnaeus that gives each species a capitalized genus name and a lowercase specific epithet, both italicized.

Adaptive radiation

The rapid diversification of a single ancestral lineage into many species occupying different ecological niches, often following colonization of new habitat.

Xylem and phloem

The two plant vascular tissues: xylem carries water and dissolved minerals upward from roots, while phloem transports sugars bidirectionally between sources and sinks.

Guard cells

Specialized epidermal cells flanking each stoma that change shape with turgor pressure to open or close the pore, balancing gas exchange against water loss.

Negative feedback

A regulatory mechanism in which a change in a variable triggers a response that reverses the change, stabilizing conditions such as body temperature and blood glucose.

Action potential

A rapid electrical signal along a neuron produced by Na⁺ influx during depolarization and K⁺ efflux during repolarization, propagating the nerve impulse.

Countercurrent exchange

A respiratory arrangement in fish gills where blood flows opposite to water flow, maintaining a concentration gradient that maximizes oxygen uptake.

Carrying capacity

The maximum population size an environment can sustain indefinitely given available resources, represented by K in the logistic growth model.

Trophic level

A feeding position in a food chain, such as producer or primary consumer; only about ten percent of energy transfers to the next level.

Nitrogen fixation

The conversion of atmospheric nitrogen gas into ammonia by bacteria such as Rhizobium in root nodules or by lightning, making nitrogen available to living organisms.

Primary succession

Ecological succession that begins on newly formed or bare substrate without soil, starting with pioneer species such as lichens and mosses and proceeding toward a climax community.

Independent variable

The factor deliberately manipulated or changed by the researcher in an experiment, whose effect on the measured dependent variable is being tested.

Safety Data Sheet

A standardized document listing a chemical's hazards, safe handling procedures, first-aid measures, and spill response, consulted before using any laboratory chemical.