FY13CE Biology flashcards

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

Hydrogen bond

A weak attraction between a partially positive hydrogen atom and a partially negative atom (usually O or N). It explains water's cohesion, high specific heat, and solvent properties.

Dehydration synthesis

A reaction that joins monomers by removing a water molecule, forming covalent bonds such as glycosidic, peptide, or phosphodiester linkages. Its reverse is hydrolysis.

Enzyme active site

The region of an enzyme where the substrate binds and catalysis occurs. Its shape determines specificity, and it can be altered by pH, temperature, or inhibitors.

Competitive inhibition

An inhibitor that binds the enzyme's active site and competes with substrate. It raises the apparent Km, but a high substrate concentration can still reach the normal Vmax.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of lower solute concentration to one of higher solute concentration, equalizing water potential.

Oxidative phosphorylation

The final stage of aerobic respiration in the inner mitochondrial membrane, where electron transport drives chemiosmotic ATP synthesis and oxygen is the final electron acceptor.

Semiconservative replication

DNA replication in which each new double helix contains one original parental strand and one newly synthesized strand, following complementary base pairing by DNA polymerase.

Transcription

Synthesis of an mRNA molecule from a DNA template by RNA polymerase, occurring in the nucleus of eukaryotes and producing a transcript complementary to the template strand.

Law of segregation

Mendel's principle that the two alleles of a gene separate during meiosis so each gamete carries only one allele, restoring pairs at fertilization.

Testcross

A cross of an individual of unknown genotype with a homozygous recessive individual; the offspring phenotypes reveal whether the unknown was homozygous dominant or heterozygous.

Codominance

A relationship in which both alleles are fully expressed in the heterozygote, as in AB blood type, rather than blending into an intermediate phenotype.

Crossing over

Exchange of corresponding chromosome segments between homologous chromatids during prophase I of meiosis, creating new combinations of alleles on a chromosome.

Frameshift mutation

An insertion or deletion of a number of nucleotides not divisible by three, which shifts the reading frame and alters all downstream amino acids.

Natural selection

Differential survival and reproduction of individuals with heritable traits better suited to the environment, causing allele frequencies in a population to change over generations.

Hardy–Weinberg equilibrium

The null model in which allele and genotype frequencies stay constant across generations under no mutation, no migration, random mating, infinite population, and no selection.

Genetic drift

Random change in allele frequencies due to chance, strongest in small populations. Bottleneck and founder effects are examples that reduce genetic variation.

Homologous structures

Body parts in different species that share common ancestry and similar underlying anatomy, such as forelimbs of mammals, even when their functions differ.

Endosymbiotic theory

The proposal that mitochondria and chloroplasts originated from prokaryotes engulfed by ancestral eukaryotic cells, supported by their own DNA and ribosomes.

Binomial nomenclature

The two-part scientific naming system: capitalized genus followed by lowercase species epithet, both italicized, used to identify every species uniquely.

Negative feedback

A homeostatic mechanism in which a deviation from a set point triggers a response that reverses the deviation, as in insulin lowering high blood glucose.

Action potential

A rapid, all-or-none electrical signal along a neuron produced by Na+ influx and K+ efflux, propagating impulses and triggering neurotransmitter release at synapses.

Transpiration

Loss of water vapor from leaves through stomata, creating tension that pulls water upward through xylem by cohesion-tension, also cooling the plant.

Auxin

A plant hormone that promotes cell elongation and mediates phototropism by accumulating on the shaded side of a stem, causing bending toward light.

Antibody

A Y-shaped protein produced by plasma B cells that binds a specific antigen, marking pathogens for neutralization or destruction in the humoral immune response.

Carrying capacity

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

Keystone species

A species whose influence on community structure is disproportionate to its abundance; its removal triggers major changes in the ecosystem.

Competitive exclusion

The principle that two species competing for the same limiting resource cannot coexist indefinitely; one outcompetes the other unless niches differentiate.

Secondary succession

Ecological succession that follows a disturbance leaving soil intact, such as fire or abandoned farmland, progressing from fast-growing plants to a mature community.

Nitrogen fixation

Conversion of atmospheric N2 into ammonia by bacteria such as Rhizobium in root nodules or by lightning, making nitrogen available for building amino acids.

Control group

In an experiment, the group not exposed to the independent variable, used as a baseline for comparison to isolate the treatment's effect.

Standard deviation

A statistic measuring the spread of data around the mean; a large value indicates high variability among observations in the sample.

Falsifiable hypothesis

A testable, specific prediction that could be shown false by observation or experiment; unfalsifiable statements cannot be evaluated scientifically.