#separator:tab #html:false #tags column:4 Enzyme A protein that speeds up a chemical reaction by lowering activation energy tp-ap-biology Substrate The molecule an enzyme acts upon tp-ap-biology Active site The region of an enzyme where the substrate binds tp-ap-biology Activation energy Energy needed to start a reaction tp-ap-biology Competitive inhibitor A molecule that blocks the active site tp-ap-biology Allosteric regulation Control of an enzyme by binding at a site other than the active site tp-ap-biology Denaturation Loss of a protein's shape and function tp-ap-biology Hydrogen bond A weak attraction between a partly positive hydrogen and a partly negative atom tp-ap-biology Cohesion Attraction between molecules of the same substance tp-ap-biology Adhesion Attraction between different substances tp-ap-biology Polar molecule A molecule with uneven charge distribution tp-ap-biology Monomer A small unit that links with others to make a polymer tp-ap-biology Dehydration synthesis Joining monomers by removing water tp-ap-biology Hydrolysis Breaking a polymer by adding water tp-ap-biology Carbohydrate Sugars and starches; main quick energy source tp-ap-biology Lipid Fats, oils and steroids; not water-soluble tp-ap-biology Phospholipid A lipid with a hydrophilic head and hydrophobic tails; forms membranes tp-ap-biology Nucleic acid DNA or RNA; stores and carries genetic information tp-ap-biology Peptide bond The covalent link between amino acids tp-ap-biology Primary protein structure The sequence of amino acids tp-ap-biology Secondary protein structure Alpha helices and beta sheets formed by hydrogen bonds tp-ap-biology Tertiary protein structure The overall 3-D folding of one polypeptide tp-ap-biology Quaternary protein structure Several polypeptides joined together tp-ap-biology Fluid mosaic model The membrane is a flexible layer of lipids with embedded proteins tp-ap-biology Diffusion Movement of molecules from high to low concentration tp-ap-biology Osmosis Diffusion of water across a selectively permeable membrane tp-ap-biology Facilitated diffusion Passive transport through a channel or carrier protein tp-ap-biology Active transport Movement against a gradient using energy tp-ap-biology Endocytosis Cell takes in material by folding the membrane around it tp-ap-biology Exocytosis Cell releases material by vesicles fusing with the membrane tp-ap-biology Hypotonic solution Lower solute concentration than the cell; cell gains water tp-ap-biology Hypertonic solution Higher solute concentration than the cell; cell loses water tp-ap-biology Isotonic solution Equal solute concentration; no net water movement tp-ap-biology Water potential A measure of water's tendency to move; it moves from high to low tp-ap-biology Nucleus Organelle holding DNA tp-ap-biology Rough ER Studded with ribosomes; makes proteins for export tp-ap-biology Smooth ER Makes lipids and detoxifies tp-ap-biology Golgi apparatus Modifies, sorts and packages proteins tp-ap-biology Lysosome Organelle containing digestive enzymes tp-ap-biology Endosymbiosis Theory that mitochondria and chloroplasts came from engulfed prokaryotes tp-ap-biology ATP The cell's main energy currency tp-ap-biology Glycolysis Splitting glucose into two pyruvate in the cytoplasm tp-ap-biology Krebs cycle Reactions in the mitochondrial matrix that release CO2 and carry electrons tp-ap-biology Oxidative phosphorylation ATP production using the electron transport chain and chemiosmosis tp-ap-biology Chemiosmosis ATP made as protons flow back through ATP synthase tp-ap-biology Fermentation Making ATP without oxygen by regenerating NAD+ tp-ap-biology Light reactions Photosynthesis stage in thylakoids that makes ATP, NADPH and O2 tp-ap-biology Calvin cycle Stage that uses ATP and NADPH to build sugar from CO2 tp-ap-biology Rubisco The enzyme that fixes carbon dioxide in the Calvin cycle tp-ap-biology Chlorophyll The main pigment that absorbs light for photosynthesis tp-ap-biology Photosystem A cluster of pigments and proteins that captures light energy tp-ap-biology Cell cycle The ordered life of a cell from one division to the next tp-ap-biology Interphase G1, S and G2: growth and DNA copying tp-ap-biology Mitosis Nuclear division producing two identical nuclei tp-ap-biology Cytokinesis Division of the cytoplasm tp-ap-biology Checkpoint A control point that decides whether the cell cycle continues tp-ap-biology Cyclin A protein that regulates progress through the cell cycle tp-ap-biology Meiosis Two divisions that produce four haploid cells tp-ap-biology Crossing over Exchange of DNA between homologous chromosomes in prophase I tp-ap-biology Independent assortment Random orientation of chromosome pairs, creating variety tp-ap-biology Nondisjunction Failure of chromosomes to separate properly tp-ap-biology Allele A version of a gene tp-ap-biology Genotype The set of alleles an individual has tp-ap-biology Phenotype The observable trait tp-ap-biology Homozygous Having two identical alleles for a gene tp-ap-biology Heterozygous Having two different alleles for a gene tp-ap-biology Law of segregation The two alleles for a gene separate into different gametes tp-ap-biology Law of independent assortment Genes for different traits are inherited independently if on separate chromosomes tp-ap-biology Incomplete dominance Heterozygote shows a blend of the two phenotypes tp-ap-biology Codominance Both alleles are fully expressed tp-ap-biology Sex-linked trait A trait whose gene lies on a sex chromosome tp-ap-biology Linked genes Genes close together on a chromosome that tend to be inherited together tp-ap-biology Replication Copying DNA before cell division tp-ap-biology Semiconservative Each new DNA molecule has one old and one new strand tp-ap-biology DNA polymerase Enzyme that adds nucleotides during replication tp-ap-biology Helicase Enzyme that unwinds the DNA double helix tp-ap-biology Okazaki fragments Short DNA pieces made on the lagging strand tp-ap-biology Transcription Making RNA from a DNA template tp-ap-biology Translation Making a protein from mRNA at a ribosome tp-ap-biology Codon Three mRNA bases that code for one amino acid tp-ap-biology Anticodon Three tRNA bases that pair with a codon tp-ap-biology Intron A noncoding region removed from RNA tp-ap-biology Exon A coding region kept in mature RNA tp-ap-biology Operon A cluster of bacterial genes controlled together tp-ap-biology Lac operon An inducible operon that lets bacteria digest lactose when it is present tp-ap-biology Transcription factor A protein that helps turn genes on or off tp-ap-biology Point mutation A change in a single DNA nucleotide tp-ap-biology Frameshift mutation An insertion or deletion that shifts the reading frame tp-ap-biology PCR A technique for copying a specific DNA segment many times tp-ap-biology Gel electrophoresis Separating DNA fragments by size using an electric current tp-ap-biology Restriction enzyme Enzyme that cuts DNA at a specific sequence tp-ap-biology CRISPR A gene-editing tool derived from a bacterial defense system tp-ap-biology Recombinant DNA DNA combined from different sources tp-ap-biology Natural selection Individuals with helpful heritable traits leave more offspring tp-ap-biology Fitness An organism's success at passing on its genes tp-ap-biology Genetic drift Random change in allele frequencies, strongest in small populations tp-ap-biology Gene flow Movement of alleles between populations tp-ap-biology Founder effect Drift caused by a small group starting a new population tp-ap-biology Bottleneck effect Drift caused by a sharp drop in population size tp-ap-biology Hardy-Weinberg equilibrium A model of a non-evolving population: p + q = 1 tp-ap-biology Speciation Formation of new species tp-ap-biology Allopatric speciation Species form after geographic separation tp-ap-biology Homologous structures Similar structures due to shared ancestry tp-ap-biology Analogous structures Similar function from separate evolution tp-ap-biology Phylogenetic tree A diagram of evolutionary relationships tp-ap-biology Cladogram A branching diagram based on shared derived traits tp-ap-biology Endothermic Producing body heat from metabolism tp-ap-biology Negative feedback A response that reduces the original change tp-ap-biology Positive feedback A response that amplifies the original change tp-ap-biology Signal transduction A pathway converting a signal outside the cell into a response inside tp-ap-biology Ligand A molecule that binds to a receptor tp-ap-biology Second messenger A small molecule that spreads a signal inside the cell, like cAMP tp-ap-biology Apoptosis Programmed cell death tp-ap-biology Carrying capacity The maximum population an environment can support tp-ap-biology Logistic growth S-shaped growth that levels off at carrying capacity tp-ap-biology Exponential growth J-shaped growth with unlimited resources tp-ap-biology Keystone species A species with a large effect on its community relative to its numbers tp-ap-biology Trophic level A feeding level in a food chain tp-ap-biology Primary productivity Rate at which producers store energy tp-ap-biology Biogeochemical cycle Movement of an element between living things and the environment tp-ap-biology Niche The role and conditions an organism needs in its ecosystem tp-ap-biology Competitive exclusion Two species needing the same resource cannot coexist indefinitely tp-ap-biology Succession Gradual change in a community over time tp-ap-biology