ORELA Biology (NT316) key terms

A thin phospholipid bilayer surrounding the cytoplasm that controls which substances enter and leave the cell, and that carries proteins used in signaling and transport.

The net movement of particles from an area of higher concentration to an area of lower concentration, driven by random molecular motion and requiring no added energy.

The diffusion of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration, driven by solute differences.

Movement of substances across a membrane against their concentration gradient, powered by cellular energy such as ATP, often through pump proteins like the sodium-potassium pump.

A solution with a higher solute concentration than the cell placed in it, causing water to leave the cell and the cell to shrink or shrivel.

A solution with a lower solute concentration than the cell placed in it, causing water to enter the cell and the cell to swell, possibly bursting.

A difference in the concentration of a substance between two regions, which provides the driving force for diffusion and is consumed by active transport.

A membrane-bound organelle in eukaryotic cells where aerobic cellular respiration occurs; it generates most of the cell's ATP and contains its own DNA.

A plastid organelle found in plant cells and algae that contains chlorophyll and is the site of photosynthesis, converting light energy into chemical energy.

A small structure made of RNA and protein, found free in the cytoplasm or attached to the rough endoplasmic reticulum, where amino acids are assembled into proteins.

The membrane-bound organelle in eukaryotic cells that houses the chromosomes and controls gene expression, serving as the cell's main regulatory center.

A type of nuclear division producing two genetically identical daughter nuclei, used for growth, repair, and asexual reproduction in eukaryotic organisms.

A two-stage reduction division that produces four haploid gametes from one diploid cell, creating genetic variation through crossing over and independent assortment.

The exchange of corresponding chromosome segments between homologous chromosomes during prophase I of meiosis, which produces new combinations of alleles.

Adenosine triphosphate, the main energy-carrying molecule of cells; releasing its terminal phosphate group supplies energy for many cellular reactions and processes.

The set of metabolic reactions in which cells break down glucose, often using oxygen, to release energy stored in ATP with carbon dioxide and water as waste products.

The first stage of cellular respiration, occurring in the cytoplasm, in which one glucose molecule is split into two pyruvate molecules with a net gain of two ATP.

The process by which green plants, algae, and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen inside chloroplasts.

A protein catalyst that speeds up a specific biochemical reaction by lowering its activation energy, without being consumed, and whose shape determines its substrate specificity.

The specific reactant molecule that binds to an enzyme's active site, forming an enzyme-substrate complex before being converted into products.

The loss of a protein's three-dimensional shape, and therefore its function, caused by heat, extreme pH, or certain chemicals that disrupt bonds holding the structure together.

The semiconservative process in which a DNA double helix unwinds and each strand templates a new complementary strand, producing two identical DNA molecules before cell division.

The synthesis of an RNA molecule from a DNA template, carried out by RNA polymerase, which transfers genetic information from the nucleus to the cytoplasm.

The process at ribosomes in which messenger RNA codons are read and transfer RNA delivers matching amino acids, building a polypeptide chain in the order specified.

A sequence of three consecutive nucleotides in messenger RNA that specifies one amino acid or a stop signal during protein synthesis.

One of two or more alternative versions of a gene at the same locus on a chromosome, which may produce different observable traits in an organism.

The particular combination of alleles an organism carries for a given gene or set of genes, which interacts with the environment to produce observable traits.

The observable physical or biochemical characteristics of an organism, resulting from the interaction between its genotype and environmental influences.

The evolutionary mechanism in which individuals with heritable traits better suited to their environment survive and reproduce more, increasing those traits in later generations.

A heritable trait or behavior that improves an organism's ability to survive and reproduce in its particular environment, arising over generations through natural selection.

The maintenance of a relatively stable internal environment within an organism, such as constant body temperature or blood glucose, despite changes in external conditions.

A regulatory mechanism in which a change in a variable triggers a response that counteracts the change, restoring the variable toward its normal set point.

An organism, usually a photosynthetic plant or alga, that makes its own organic food from inorganic substances and forms the base of a food web.

An organism that cannot make its own food and obtains energy by eating other organisms, classified as primary, secondary, or tertiary depending on its position in a food chain.

An organism such as a bacterium or fungus that breaks down dead organic matter, recycling nutrients back into the ecosystem.

The maximum population size of a species that a given environment can support indefinitely, determined by available resources such as food, water, and space.

A close, long-term interaction between individuals of two different species, which may benefit both partners, benefit one at the other's expense, or benefit one while harming neither.

A large terrestrial region characterized by a particular climate and dominated by distinctive plant and animal communities, such as desert, grassland, or tropical rainforest.