FY13CE Biology key terms

A large molecule built by joining many smaller units, such as a protein assembled from amino acids. The four main kinds in living things are carbohydrates, lipids, proteins, and nucleic acids.

A molecule made of many repeating small subunits linked together. Starch, DNA, and proteins are examples, each built from its own type of monomer.

A single small unit that can be joined to identical or similar units to build a polymer. Sugars, amino acids, and nucleotides serve as monomers for larger molecules.

The building block of proteins; twenty standard kinds differ in their side chains. Their order in a chain determines how the protein folds and what it does.

The chemical link formed between the carboxyl group of one amino acid and the amino group of the next, releasing water. It joins amino acids into a chain.

A protein that speeds up a specific reaction by lowering the energy needed to start it. Each enzyme has a shape-matched active site where substrate binds.

Loss of a protein's functional shape caused by heat, extreme pH, or salt changes. Because structure determines function, a denatured enzyme usually stops working.

The minimum energy input required for a chemical reaction to proceed. Enzymes reduce this barrier, so reactions happen faster at normal body temperatures.

A substance that speeds a reaction without being consumed by it. In cells, most catalysts are enzymes, and they can be used repeatedly.

A chain of amino acids folded into a specific three-dimensional shape. Proteins serve as enzymes, structural fibers, transporters, hormones, and signaling molecules.

The monomer of nucleic acids, made of a phosphate group, a five-carbon sugar, and a nitrogenous base. It also appears in ATP, the cell's energy carrier.

A double-stranded nucleic acid storing hereditary information in its base sequence. Its sugar is deoxyribose, and its bases are adenine, thymine, guanine, and cytosine.

A usually single-stranded nucleic acid containing ribose and uracil instead of thymine. Messenger, transfer, and ribosomal forms carry out protein synthesis.

The process in which RNA polymerase builds an RNA copy from a DNA template. In eukaryotes it occurs in the nucleus and produces messenger RNA for export.

The process in which ribosomes read messenger RNA codons and assemble amino acids into a protein. Transfer RNA delivers each amino acid matching the codon.

A sequence of three RNA bases that specifies one amino acid or a stop signal. The genetic code is nearly universal across organisms.

The copying of a DNA molecule before cell division. Each strand serves as a template, so each new double helix keeps one original strand.

A change in the base sequence of DNA. It may be silent, alter a protein, or shift the reading frame, and it is the original source of genetic variation.

One of the alternative versions of a gene at a given locus. An organism inherits two alleles for each gene, one from each parent.

The particular combination of alleles an organism carries for a gene or set of genes. It is written with letters showing dominant and recessive forms.

The observable traits of an organism, such as eye color or blood type. It results from genotype interacting with the environment.

A two-stage cell division that halves chromosome number and produces four genetically varied gametes. Crossing over and independent assortment create new allele combinations.

Division of a nucleus producing two daughter cells with the same chromosome number as the parent. It supports growth, repair, and asexual reproduction.

Exchange of chromosome segments between homologous chromosomes during meiosis. It breaks up linked alleles and increases genetic variety in offspring.

A reproductive cell such as a sperm or egg, carrying half the usual chromosome number. Gametes fuse at fertilization to restore the full set.

The cell formed when two gametes fuse, containing a complete set of chromosomes. It divides repeatedly to develop into a new organism.

The process by which individuals with traits better suited to their environment tend to survive and reproduce more, so those traits become more common over generations.

An inherited trait that improves an organism's chance of surviving and reproducing in its environment. Adaptations arise over generations through natural selection.

An organism's relative contribution of offspring to the next generation. It measures reproductive success, not physical strength or health alone.

The formation of new species, usually when populations become reproductively isolated and stop exchanging genes. Isolation may be geographic or arise through other barriers.

The maintenance of stable internal conditions such as temperature, pH, and blood sugar despite outside change. Feedback loops detect and correct deviations.

A control mechanism in which a change triggers a response that reverses that change, restoring the set point. Body temperature and blood glucose regulation are examples.

The net movement of particles from regions of higher concentration to lower concentration. It requires no energy input and drives gas exchange across membranes.

The diffusion of water across a selectively permeable membrane toward the side with higher solute concentration. It affects cell volume and shape.

The process by which plants and other producers use light energy to convert carbon dioxide and water into sugars, releasing oxygen. It occurs in chloroplasts.

The breakdown of glucose, with oxygen in aerobic cells, to release energy stored as ATP. It produces carbon dioxide and water as waste products.

Adenosine triphosphate, the molecule that carries usable energy within cells. Breaking off its terminal phosphate releases energy for cellular work.

A plant cell organelle containing chlorophyll and the membranes where photosynthesis occurs. It captures light energy to make sugars.

A structure of RNA and protein where amino acids are linked into proteins. It reads messenger RNA and is found free in cytoplasm or attached to membranes.

The largest population size an environment can sustain over time given available resources. Growth slows as a population approaches this limit.

A group of individuals of the same species living in the same area at the same time. Populations are the units in which evolution and ecology are measured.

Interaction in which organisms need the same limited resource, such as food, water, or space. It can limit growth of both species involved.

A network of feeding relationships showing how energy and matter move among producers, consumers, and decomposers. Arrows point in the direction energy flows.

A feeding position in a food chain, such as producer, primary consumer, or secondary consumer. Only a small fraction of energy passes to the next level.

An organism such as a fungus or bacterium that breaks down dead matter, releasing nutrients back to the environment. Decomposers recycle matter through ecosystems.

A testable, tentative explanation for an observation, stated so it could be shown false. It guides what data a scientist collects.

A study that changes one factor while holding others constant and compares treated and untreated groups. This design supports cause-and-effect conclusions.

The factor a researcher deliberately changes or manipulates in an experiment. Its effect is measured through the dependent variable.

The factor measured or observed in an experiment; it responds to changes in the independent variable. It provides the data used to test the hypothesis.