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| 10153993234 | activation energy | The energy that must be possessed by atoms or molecules in order to react. | 0 | |
| 10153993235 | active site | The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds. | 1 | |
| 10153993236 | active transport | The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins. | 2 | |
| 10153993237 | adhesion | The tendency of different kinds of molecules to stick together. | 3 | |
| 10153993238 | aerobic | Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen. | 4 | |
| 10153993239 | amino acid | An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins. | 5 | |
| 10153993240 | anaerobic | Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it. | 6 | |
| 10153993241 | antibiotic | A chemical that kills bacteria or inhibits their growth. | 7 | |
| 10153993242 | asexual reproduction | A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts. | 8 | |
| 10153993243 | atom | The smallest unit of matter that retains the properties of an element. | 9 | |
| 10153993244 | adenosine triphosphate (ATP) | An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells. | 10 | |
| 10153993245 | autotroph | An organism that obtains organic food molecules without eating other organisms. The organisms use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones. | 11 | |
| 10153993246 | binary fission | The type of cell division by which prokaryotes reproduce; each dividing daughter cell receives a copy of the single parental chromosome. | 12 | |
| 10153993247 | brain stem | The hindbrain and midbrain of the vertebrate central nervous system. In humans, it forms a cap on the anterior end of the spinal cord, extending to about the middle of the brain. | 13 | |
| 10153993248 | carbohydrate | A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides). | 14 | |
| 10153993249 | catalyst | A substance that lowers the activation energy of a chemical reaction by forming a temporary association with the reacting molecules; as a result, the rate of the reaction is accelerated. Enzymes are this type of substance. | 15 | |
| 10153993250 | cell | A basic unit of living matter separated from its environment by a plasma membrane; the fundamental structural unit of life. | 16 | |
| 10153993251 | cell theory | All living things are composed of cells; cells arise only from other cells. No exception has been found to these two principles since they were first proposed well over a century ago. | 17 | |
| 10153993252 | cellular respiration | The most prevalent and efficient catabolic pathway for the production of ATP, in which oxygen is consumed as a reactant along with the organic fuel. | 18 | |
| 10153993253 | cerebellum | Part of the vertebrate hindbrain; functions in unconscious coordination of movement and balance. | 19 | |
| 10153993254 | cerebrum | The dorsal portion, composed of right and left hemispheres, of the vertebrate forebrain; the integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system. | 20 | |
| 10153993255 | chemical reaction | A process leading to chemical changes in matter; involves the making and/or breaking of chemical bonds. | 21 | |
| 10153993256 | chloroplast | An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water. | 22 | |
| 10153993257 | chromosome | A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin. | 23 | |
| 10153993258 | cohesion | The binding together of like molecules, often by hydrogen bonds. | 24 | |
| 10153993259 | covalent bond | A chemical bond formed as a result of the sharing of one or more pairs of electrons. | 25 | |
| 10153993260 | crossing over | The reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I. | 26 | |
| 10153993261 | denature | destroy the characteristic properties of (a protein or other biological macromolecule) by heat, acidity, or other effects that disrupt its molecular conformation. | 27 | |
| 10153993262 | dependent variable | In an experiment, the factor that responds and is measured when another factor is manipulated. | 28 | |
| 10153993263 | dermal tissue system | The protective covering of plants; generally a single layer of tightly packed epidermal cells covering young plant organs formed by primary growth. | 29 | |
| 10153993264 | diffusion | The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area. | 30 | |
| 10153993265 | diploid cell | A cell containing two sets of chromosomes (2n), one set inherited from each parent. | 31 | |
| 10153993266 | deoxyribonucleic acid (DNA) | A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins. | 32 | |
| 10153993267 | endosymbiotic theory | A hypothesis about the origin of the eukaryotic cell, maintaining that the forerunners of eukaryotic cells were symbiotic associations of prokaryotic cells living inside larger prokaryotes. | 33 | |
| 10153993268 | enzyme | A class of proteins serving as catalysts, chemical agents that change the rate of a reaction without being consumed by the reaction. | 34 | |
| 10153993269 | eukaryote | An organism whose cells contain membraine-bound organelles and whose DNA is enclosed in a cell nucleus and is associated with proteins. | 35 | |
| 10153993270 | fatty acid | A long carbon chain carboxylic acid. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat. | 36 | |
| 10153993271 | feedback inhibition | A method of metabolic control in which the end-product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway. | 37 | |
| 10153993272 | fermentation | A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end-product, such as ethyl alcohol or lactic acid. | 38 | |
| 10153993273 | fluid mosaic model | The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids. | 39 | |
| 10153993274 | gamete | A haploid egg or sperm cell; gametes unite during sexual reproduction to produce a diploid zygote. | 40 | |
| 10153993275 | glycerol | A three-carbon molecule with three hydroxyl (−OH) groups attached; a glycerol molecule can combine with three fatty acid molecules to form a fat or an oil. | 41 | |
| 10153993276 | guard cell | A specialized epidermal plant cell that forms the boundaries of the stomata. | 42 | |
| 10153993277 | haploid cell | A cell containing only one set of chromosomes (n). | 43 | |
| 10153993278 | heterotroph | An organism that obtains organic food molecules by eating other organisms or their by-products. | 44 | |
| 10153993279 | homeostasis | The steady-state physiological condition of the body. | 45 | |
| 10153993280 | homologous chromosomes | Chromosome pairs of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. | 46 | |
| 10153993281 | hydrogen bond | A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule. | 47 | |
| 10153993282 | hypertonic solution | A solution with a greater solute concentration than another, a hypotonic solution. | 48 | |
| 10153993283 | hypothesis | A temporary working explanation or supposition based on accumulated facts and suggesting some general principle or relation of cause and effect; a postulated solution to a scientific problem that must be tested and if not validated, discarded. | 49 | |
| 10153993284 | hypotonic solution | A solution with a lesser solute concentration than another, a hypertonic solution. | 50 | |
| 10153993285 | independent variable | In an experiment, when one factor is manipulated, a second factor responds. The independent variable is the factor that is manipulated. | 51 | |
| 10153993286 | inflammatory response | A line of defense triggered by penetration of the skin or mucous membranes, in which small blood vessels in the vicinity of an injury dilate and become leakier, enhancing the infiltration of leukocytes; may also be widespread in the body. | 52 | |
| 10153993287 | ion | An atom that has gained or lost electrons, thus acquiring a charge. | 53 | |
| 10153993288 | isotonic solution | Solutions of equal solute concentration. | 54 | |
| 10153993289 | joule (J) | A unit of energy equal to 0.239 cal | 55 | |
| 10153993290 | lipid | One of a family of compounds, including fats, phospholipids, and steroids, that are insoluble in water. | 56 | |
| 10153993291 | lymphocyte | A white blood cell. The lymphocytes that complete their development in the bone marrow are called B cells, and those that mature in the thymus are called T cells. | 57 | |
| 10153993292 | mean | The average of a set of numbers. You find the average of a set of numbers by adding them up and dividing by the number of numbers in the set. | 58 | |
| 10153993293 | macromolecule | A giant molecule of living matter formed by the joining of smaller molecules, usually by a condensation reaction (dehydration synthesis). Polysaccharides, proteins, and nucleic acids are macromolecules. | 59 | |
| 10153993294 | mechanism | an explanation of how a process or phenomenon works or might work. | 60 | |
| 10153993295 | meiosis | A two-stage type of cell division in sexually reproducing organisms that results in gametes with half the chromosome number of the original cell. | 61 | |
| 10153993296 | metabolism | The totality of an organism's chemical processes, consisting of catabolic and anabolic pathways. | 62 | |
| 10153993297 | mitochondrion (pl. mitochondria) | An organelle in eukaryotic cells that serves as the site of cellular respiration. | 63 | |
| 10153993298 | mitosis | A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei. | 64 | |
| 10153993299 | molecule | Two or more atoms held together by covalent bonds. | 65 | |
| 10153993300 | monomer | The subunit that serves as the building block of a polymer. | 66 | |
| 10153993301 | monosaccharide | The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, the molecular formulas of monosaccharides are generally some multiple of CH2O. | 67 | |
| 10153993302 | nucleic acid | A polymer consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA. | 68 | |
| 10153993303 | nucleotide | The building block of a nucleic acid, consisting of a five-carbon sugar covently bonded to a nitrogenous base and a phosphate group. | 69 | |
| 10153993332 | nucleus | (1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons. | 70 | |
| 10153993304 | organelle | One of several formed bodies with a specialized function, suspended in the cytoplasm and found in eukaryotic cells. | 71 | |
| 10153993305 | organic | Pertaining to (1) organisms or living things generally, or (2) compounds formed by living organisms, or (3) the chemistry of compounds containing carbon. | 72 | |
| 10153993306 | osmosis | The diffusion of water across a selectively permeable membrane. | 73 | |
| 10153993307 | passive transport | The diffusion of a substance across a biological membrane. | 74 | |
| 10153993308 | pathogen | An organism or a virus that causes disease. | 75 | |
| 10153993309 | pH scale | A measure of hydrogen ion concentration equal to −log [H+] and ranging in value from 0 to 14. | 76 | |
| 10153993310 | phenotype | The physical and physiological traits of an organism. | 77 | |
| 10153993311 | phospholipids | Molecules that constitute the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail. | 78 | |
| 10153993312 | plasma membrane | The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell's chemical composition. | 79 | |
| 10153993313 | polar molecule | A molecule (such as water) with opposite charges on opposite sides. | 80 | |
| 10153993314 | polymer | A large molecule consisting of many identical or similar monomers linked together. | 81 | |
| 10153993315 | polypeptide | A polymer (chain) of many amino acids linked together by peptide bonds. | 82 | |
| 10153993316 | polysaccharide | A polymer of up to over a thousand monosaccharides, formed by condensation synthesis. | 83 | |
| 10153993317 | prokaryotic cell | A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea. | 84 | |
| 10153993318 | protein | A three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids. | 85 | |
| 10153993333 | rate | A measure, quantity, or frequency, typically one measured against some other quantity or measure. | 86 | |
| 10153993319 | reactant | A starting material in a chemical reaction. | 87 | |
| 10153993320 | ribosome | A cell organelle constructed in the nucleolus, functioning as the site of protein synthesis in the cytoplasm. Consists of rRNA and protein molecules, which make up two subunits. | 88 | |
| 10153993321 | ribonucleic acid (RNA) | A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses. | 89 | |
| 10153993322 | selective permeability | A property of biological membranes that allows some substances to cross more easily than others. | 90 | |
| 10153993323 | sexual reproduction | A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents. | 91 | |
| 10153993324 | solution | A homogeneous, liquid mixture of two or more substances. | 92 | |
| 10153993325 | somatic cell | Any cell in a multicellular organism except a sperm or egg cell. | 93 | |
| 10153993326 | specific heat | The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature 1°C. | 94 | |
| 10153993327 | stoma (pl. stomata) | A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant. | 95 | |
| 10153993328 | transpiration | The evaporative loss of water from a plant. | 96 | |
| 10153993329 | vaccine | A harmless variant or derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen. | 97 | |
| 10153993330 | valence shell | The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom. | 98 | |
| 10153993331 | vascular tissue | Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body. | 99 |
