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Exam3-F
Flashcards of Biology for chapters 7,9,10,11 by Peter Raven with McGraw Hill
| Term | Definition |
|---|---|
| Autotroph | An organism able to build all the complex organic molecules that it requires as its own food source, using only simple inorganic compounds. |
| Heterotroph | An organism that cannot derive energy from photosynthesis or inorganic chemicals, and so must feed on other plants and animals, obtaining chemical energy by degrading their organic molecules. |
| Cellular Respiration | The metabolic harvesting of energy by oxidation, ultimately dependent on molecular oxygen; carried out by the citric acid cycle and oxidative phosphorylation. |
| Dehydrogenation | Chemical reaction involving the loss of a hydrogen atom. This is an oxidation that combines loss of an electron with loss of a proton. |
| Nicotinamide Adenine Dinucleotide (NAD) | A molecule that becomes reduced (to NADH) as it carries high-energy electrons from oxidized molecules and delivers them to ATP-producing pathways in the cell. |
| Aerobic Respiration | The process that results in the complete oxidation of glucose using oxygen as the final electron acceptor. Oxygen acts as the final electron acceptor for an electron transport chain that produces a proton gradient for the chemiosmotic synthesis of ATP. |
| Anaerobic Respiration | The use of electron transport to generate a proton gradient for chemiosmotic synthesis of ATP using a final electron acceptor other than oxygen. |
| Fermentation | The enzyme-catalyzed extraction of energy from organic compounds without the involvement of oxygen. |
| Electron Transport Chain | The passage of energetic electrons through a series of membrane-associated electron-carrier molecules to proton pumps embedded within mitochondrial or chloroplast membranes. |
| Glycolysis | The anaerobic breakdown of glucose; this enzyme-catalyzed process yields two molecules of pyruvate with a net of two molecules of ATP. |
| Oxidative Phosphorylation | Synthesis of ATP by ATP synthase using energy from a proton gradient generated by electron transport, which requires oxygen. |
| Glyceraldehyde-3-Phosphate | An intermediate in glycolysis that is a product of the cleavage reaction of fructose 1,6-bisphosphate. |
| NADH Dehydrogenase | An enzyme located on the inner mitochondrial membrane that catalyzes the oxidation by NAD+ of pyruvate to acetyl-CoA. This reaction links glycolysis and the citric acid cycle. |
| Deamination | The removal of an amino group; part of the degradation of proteins into compounds that can enter the Krebs cycle. |
| Beta oxidation | The oxygen-dependent reactions where 2-carbon units of fatty acids are cleaved and combined with CoA to produce acetyl-CoA, which then enters the citric acid cycle |
| Ligand | A signaling molecule that binds to a specific receptor protein initiating signal transduction in cells. |
| Receptor Protein | A cellular protein that can bind to a ligand (signaling molecule) and initiate a signal transduction pathway, Can be either a membrane protein or intracellular, depending on the nature od the ligand. |
| Paracrine | A type of chemical signaling between cells in which the effects are local and short-lived. |
| Hormone | A molecule, usually a peptide or steroid that is produced in one part of an organism and triggers a specific cellular reaction in target tissues and organs some distance away. |
| Neurotransmitter | A chemical released at the axon terminal of a neuron that travels across the synaptic cleft, binds a specific receptor on the far side, and depending on the nature of the receptor, depolarizes or hyperpolarizes a second neuron or a muscle of gland cell. |
| Chemical Synapse | A close association that allows chemical communication between neurons. A chemical signal (neurotransmitter) released by the first neuron binds to receptors in the membrane of the second neurons. |
| Signal transduction | The events that occur within a cell on receipt of a signal, ligand binding to a receptor protein, Signal transduction pathways produce the cellular response to a signaling molecule. |
| Phosphorylation | Chemical reaction resulting in the addition of a phosphate group to an organic molecule. Phosphorylation of ADP yields ATP. Many proteins are also activated or inactivated by phosphorylation. |
| Dephosphorylation | The removal of a phosphate group, usually by a phosphate enzyme. Many proteins can be activated or inactivated by dephosphorylation. |
| Phosphatase | Any number of enzymes that removes a phosphate group from a protein, reversing the action of a kinase. |
| Ion Channel | Membrane proteins that allow the passage of ions through a phospholipid bilayer. These are usually specific for a single ion, and may be found in the plasma membrane, or in internal membranes. |
| Protein Kinase | An enzyme adds phosphate groups to proteins, changing their activity. |
| G protein | A protein that binds guanosine triphosphate (GTP) and assists in the function of cell-surface receptors. When the receptor binds its signal molecule, the G protein binds GTP and is activated to start a chain of events within the cell. |
| Second messenger | A small molecule or ion that carries the message from a receptor on the target cell surface into the cytoplasm. |
| Cyclic AMP (cAMP) | A form of adenosine monophosphate (AMP) in which the atoms of the phosphate group form a ring; found in almost all organisms, cAMP functions as an intracellular second messenger that regulates a diverse array of metabolic activities. |
| Nuclear Receptor | Intracellular receptors, primarily for steroid hormones, that are found in both the cytoplasm and the nucleus. The site of action of the hormone-receptor complex is in the nucleus where they modify gene expression. |
| Coactivator | A protein that functions to link transcriptional activators to the transcription complex consisting of RNA polymerase II and general transcription factors. |
| Receptor Tyrosine Kinase (RTK) | A diverse group of membrane receptors that when activated have kinase enzymatic activity. Specifically they phosphorylate proteins on tyrosine. Their activation can lead to diverse cellular responses. |
| Plant receptor kinase | Plant membrane receptors that when activated by binding ligand have kinase enzymatic activity. These phosphorylate serine or threonine, unlike RTKs in animals that phosphorylate tyrosine. |
| Adaptor Protein | Proteins that acts as a link between a receptor and other proteins to initiate signal transduction. |
| Mitogen-activated protein (MAP) Kinase | Protein kinases that activate transcription factors to alter gene expression. A mitogen is any molecule that stimulates cell division. MAP kinases are activated by kinase cascades. |
| Kinase cascade | A series of protein kinases that phosphorylate ach other in succession; a kinase cascade can amplify signals during the signal transduction process. |
| Ras | An extensive family of small G proteins that act in signal transduction as a switch that links a membrane RTK with a kinase cascade. |
| G protein-coupled receptor (GPCR) | A receptor that acts through a heterotrimeric (three component) G protein to activate effector proteins that then function as enzymes to produce second messengers such as cAMP or IP3 |
| Adenylyl cyclase | Enzyme activated by GPCR signaling to convert ATP to cyclic AMP, which then acts as a second messenger. |
| Diacylglycerol (DAG) | A second messenger that is released, along with inositol-1,3,5-triphosphate(IP3), when phospholipase C cleaves PIP2. DAG can have a variety of cellular effects through activation of protein kinases. |
| Inositol-1,4,5-triphosphate (IP3) | Second messenger produced by the cleavage of phosphatidylinositol-4,5-bisphosphate |
| binary fission | Asexual reproduction by division of one cell or body into two equal or nearly equal parts. |
| septum/ septa | A wall between two cavities |
| septation | In prokaryotic cell division, the formation of a septum where new cell membrane and cell wall are formed to separate the two daughter cells. |
| haploid | Having only one set of chromosomes (n), in contrast to diploid (2n). |
| diploid | Having two sets of chromosomes (2n); in animals, twice the number characteristic of gametes; in plants, the chromosome number characteristic of the sporophyte generation; in contrast to haploid (n). |
| homologous | (1) Refers to similar structures that have the same evolutionary origin. (2) Refers to a pair of the same kind of chromosome in a diploid cell. |
| homologue | One of a pair of chromosomes of the same kind located in a diploid cell; one copy of each pair of homologues comes from each gamete that formed the zygote. |
| karyotype | The morphology of the chromosomes of an organism as viewed with a light microscope. |
| chromatin | The complex of DNA and proteins of which eukaryotic chromosomes are composed; chromatin is highly uncoiled and diffuse in interphase nuclei, condensing to form the visible chromosomes in prophase. |
| nucleosome | A complex consisting of a DNA duplex wound around a core of eight histone proteins. |
| histone protein | Any of eight proteins with an overall positive charge that associate in a complex. The DNA duplex coils around a core of eight histone proteins, held by its negatively charged phosphate groups, forming a nucleosome. |
| heterochromatin | The portion of a eukaryotic chromosome that is not transcribed into RNA; remains condensed in interphase and stains intensely in histological preparations. |
| euchromatin | That portion of a eukaryotic chromosome that is transcribed into mRNA; contains active genes that are not tightly condensed during interphase. |
| condensin | A protein complex involved in condensation of chromosomes during mitosis and meiosis. |
| cohesin | A protein complex that holds sister chromatids together during cell division. The loss of cohesins at the centromere allows the anaphase movement of chromosomes. |
| sister chromatid | One of two identical copies of each chromosome, still linked at the centromere, produced as the chromosomes duplicate for mitotic division; similarly, one of two identical copies of each homologous chromosome present in a tetrad at meiosis. |
| cell cycle | The repeating sequence of growth and division through which cells pass each generation. |
| G1 phase | The phase of the cell cycle after cytokinesis and before DNA replication called the first “gap” phase. This phase is the primary growth phase of a cell. |
| G2 phase | The phase of the cell cycle between DNA replication and mitosis called the second “gap” phase. During this phase, the cell prepares for mitosis. |
| interphase | The period between two mitotic or meiotic divisions in which a cell grows and its DNA replicates; includes G1, S, and G2 phases. |
| mitosis | Somatic cell division; nuclear division in which the duplicated chromosomes separate to form two genetically identical daughter nuclei. |
| cytokinesis | Division of the cytoplasm of a cell after nuclear division. |
| G0 phase | The stage of the cell cycle occupied by cells that are not actively dividing. |
| tubulin | Globular protein subunit forming the hollow cylinder of microtubules. |
| prophase | The phase of cell division that begins when the condensed chromosomes become visible and ends when the nuclear envelope breaks down. The assembly of the spindle takes place during prophase. |
| spindle apparatus | The assembly that carries out the separation of chromosomes during cell division; composed of microtubules (spindle fibers) and assembled during prophase at the equator of the dividing cell. |
| aster | In animal cell mitosis, a radial array of microtubules extending from the centrioles toward the plasma membrane, possibly serving to brace the centrioles for retraction of the spindle. |
| prometaphase | The transitional phase between prophase and metaphase during which the spindle attaches to the kinetochores of sister chromatids. |
| metaphase | The stage of mitosis or meiosis during which microtubules become organized into a spindle and the chromosomes come to lie in the spindle’s equatorial plane. |
| anaphase | In mitosis and meiosis II, the stage initiated by the separation of sister chromatids, during which the daughter chromosomes move to opposite poles of the cell; in meiosis I, marked by separation of replicated homologous chromosomes. |
| telophase | The phase of cell division during which the spindle breaks down, the nuclear envelope of each daughter cell forms, and the chromosomes uncoil and become diffuse. |
| cleavage furrow | The constriction that forms during cytokinesis in animal cells that is responsible for dividing the cell into two daughter cells. |
| cell plate | The structure that forms at the equator of the spindle during early telophase in the dividing cells of plants and a few green algae. |
| cyclin | Any of a number of proteins that are produced in synchrony with the cell cycle and combine with certain protein kinases, the cyclin-dependent kinases, at certain points during cell division. |
| cyclin-dependent kinase (Cdk) | Any of a group of protein kinase enzymes that control progress through the cell cycle. These enzymes are only active when complexed with cyclin. The cdc2 protein, produced by the cdc2 gene, was the first Cdk enzyme discovered. |
| G2/M checkpoint | The second cell-division control point, at which division can be delayed if DNA has not been properly replicated or is damaged |
| M-phase-promoting factor (MPF) | A Cdk enzyme active at the G2/M checkpoint. |
| spindle checkpoint | The third cell-division checkpoint, at which all chromosomes must be attached to the spindle. Passage through this checkpoint commits the cell to anaphase. |
| anaphase-promoting complex (APC) | A protein complex that triggers anaphase; it initiates a series of reactions that ultimately degrades cohesin, the protein complex that holds the sister chromatids together. sister chromatids are then released and move toward opposite poles in the cell |
| platelet-derived growth factor (PDGF) | A signaling molecule (growth factor) that can stimulate cell division in fibroblasts. |
| cancer | The unrestrained growth and division of cells; it results from a failure of cell division control. |
| oncogene | A mutant form of a growth-regulating gene that is inappropriately “on,” causing unrestrained cell growth and division. |
| tumor-suppressor gene | A gene that normally functions to inhibit cell division; mutated forms can lead to the unrestrained cell division of cancer, but only when both copies of the gene are mutant. |
| proto-oncogene | A normal cellular gene that can act as an oncogene when mutated. |
| retinoblastoma susceptibility gene (Rb) | A gene that, when mutated, predisposes individuals to a rare form of cancer of the retina; one of the first tumor-suppressor genes discovered. |
| gamete | A haploid reproductive cell. |
| somatic cell | Any of the cells of a multicellular organism except those that are destined to form gametes (germ-line cells). |
| zygote | The diploid (2n) cell resulting from the fusion of male and female gametes (fertilization). |
| fertilization | The fusion of two haploid gamete nuclei to form a diploid zygote nucleus. |
| syngamy | The process by which two haploid cells (gametes) fuse to form a diploid zygote; fertilization. |
| meiosis I | The first round of cell division in meiosis; it is referred to as a “reduction division” because homologous chromosomes separate, and the daughter cells have only the haploid number of chromosomes |
| sexual reproduction | The process of producing offspring through an alternation of fertilization (producing diploid cells) and meiotic reduction in chromosome number (producing haploid cells). |
| germ-line cells | During zygote development, cells that are set aside from the somatic cells and that will eventually undergo meiosis to produce gametes. |
| meiosis II | The second round of division in meiosis, during which the two haploid cells from meiosis I undergo a mitosis-like division without DNA replication to produce four haploid daughter cells. |
| synapsis | The point-by-point alignment (pairing) of homologous chromosomes that occurs before the first meiotic division; crossing over takes place during synapsis. |
| synaptonemal complex | Protein lattice forms between two homologous chromosomes in prophase I of meiosis, holding replicated chromosomes in precise register so that base-pairs can form between nonsister chromatids for crossing over that is usually exact within a gene sequence. |
| reciprocal recombination | A mechanism of genetic recombination that occurs only in eukaryotic organisms, in which two chromosomes trade segments; can occur between nonhomologous chromosomes as well as the more usual exchange between homologous chromosomes in meiosis. |
| crossing over | In meiosis, the exchange of corresponding chromatid segments between homologous chromosomes; responsible for genetic recombination between homologous chromosomes. |
| chiasma | An X-shaped figure that can be seen in the light microscope during meiosis; evidence of crossing over, where two chromatids have exchanged parts; chiasmata move to the ends of the chromosome arms as the homologues separate. |
| independent assortment | In a dihybrid cross, describes the random assortment of alleles for each of the genes. |
| achiasmate segregation | The accurate segregation of homologues during meiosis I without the formation of chiasmata between homologues. |
| aneuploidy | The condition in an organism whose cells have lost or gained a chromosome; Down syndrome, which results from an extra copy of human chromosome 21, is an example of aneuploidy in humans. |
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