CLEP Biology key terms

A thin double layer of lipids with embedded proteins that surrounds every cell and controls which substances move into and out of it.

The spontaneous movement of particles from an area where they are crowded to an area where they are less concentrated, driven by random molecular motion.

The diffusion of water across a selectively permeable membrane from a region of lower dissolved-solute concentration to a region of higher solute concentration.

A protein that speeds up a specific chemical reaction by lowering the energy needed to start it, without being consumed in the process.

The small pocket on an enzyme where substrate molecules bind and where the chemical reaction is actually catalyzed.

The molecule or molecules that an enzyme binds and converts into products during a catalyzed reaction.

Adenosine triphosphate, a small molecule whose phosphate bonds store energy; cells break it down to power most energy-requiring processes.

The first stage of glucose breakdown, occurring in the cytoplasm, which splits one glucose into two pyruvate molecules and yields a small amount of ATP.

The oxygen-requiring series of reactions in which cells break down glucose and release energy that is captured as ATP, with carbon dioxide and water as waste products.

An anaerobic pathway that regenerates a needed coenzyme by converting pyruvate into products such as lactate or ethanol, allowing glycolysis to continue without oxygen.

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

The green pigment in chloroplasts that absorbs light energy and donates excited electrons to begin the reactions of photosynthesis.

The process in which a double-stranded DNA molecule is copied, with each original strand serving as a template for a new complementary strand.

Deoxyribonucleic acid, the double-stranded molecule that stores genetic information in the sequence of its four nucleotide bases.

The synthesis of an RNA molecule from a DNA template, carried out by RNA polymerase in the nucleus of eukaryotic cells.

The process in which ribosomes read messenger RNA and assemble the corresponding chain of amino acids to form a protein.

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

A change in the nucleotide sequence of DNA, which can alter the protein produced and is the ultimate source of genetic variation.

The type of nuclear division that produces two genetically identical daughter cells and is used for growth and repair of body tissues.

The specialized cell division that halves the chromosome number and produces genetically varied gametes such as eggs and sperm.

The exchange of matching chromosome segments between paired homologous chromosomes during meiosis, which creates new combinations of alleles.

The ordered sequence of growth, DNA duplication, and division that a cell passes through between one division and the next.

One of the alternate versions of a gene that can occupy the same position on a chromosome and may produce different traits.

The particular combination of alleles an organism carries for a gene or set of genes.

The observable characteristics of an organism, resulting from the interaction between its genotype and its environment.

The tendency of an organism to keep internal conditions such as temperature and blood chemistry within a stable, workable range.

A control mechanism in which a change in a body condition triggers a response that reverses that change and restores the original state.

A chemical messenger released by a gland or cell that travels through the body and alters the activity of target cells bearing matching receptors.

A nerve cell specialized to receive, conduct, and transmit electrical impulses; it is the basic signaling unit of the nervous system.

A chemical released at the end of a neuron that crosses a small gap and carries the signal to the next cell.

A reproductive cell, such as an egg or sperm, that carries half the usual chromosome number and fuses with another gamete at fertilization.

The single cell formed when two gametes fuse, which then divides repeatedly to develop into a new organism.

The process by which individuals with inherited traits that improve survival and reproduction leave more offspring, so those traits become more common over generations.

An inherited feature of an organism that improves its ability to survive and reproduce in its particular environment.

The relative contribution an individual makes to the next generation's gene pool, usually measured as the number of surviving offspring it produces.

The proportion of all copies of a gene in a population that are represented by one particular allele.

A random change in allele frequencies from one generation to the next, especially pronounced in small populations, caused by chance rather than selection.

The movement of alleles between populations when individuals migrate and breed, which tends to reduce genetic differences among populations.

The maximum population size of a species that a given environment can support indefinitely with the resources available.

Any resource or condition, such as food, water, or space, that restricts the growth or size of a population.

The change in the number of individuals in a population over time, influenced by births, deaths, immigration, and emigration.

A feeding position in a food chain, such as producer, primary consumer, or secondary consumer, defined by how many steps energy has traveled.

A network of interconnected food chains that shows the many feeding relationships among organisms in a community.

A diagram showing that only a small fraction of the energy at one trophic level is passed on to the next, so higher levels support fewer organisms.

A close, long-term living arrangement between individuals of two different species, which may benefit both, benefit one, or harm one.