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Bio 4 Exam
| Term | Definition |
|---|---|
| Cell Signaling | the ability for all cells to produce, receive, and respond to external signals/conditions. |
| Ligand | a small signaling molecule that binds and forms a complex with a biomolecule/receptor. |
| Receptor | biomolecule (protein) that changes shape (or conformation) upon ligand binding. |
| 1st step of Cell Signaling | Receptor recognition/binding of signal signal |
| 2nd step of cell signaling | Signal transduction/ intracellular signaling |
| 3rd step of cell signaling | cell response/ target proteins |
| 4th step of cell signaling | turn off the signal |
| G-protein coupled receptor (GPCR) | Transmembrane receptor, 7-pass, works with G-proteins |
| G-proteins act as | a molecular switch that use GTP/GDP to turn on/off signaling |
| Bound GTP | on or activated |
| bound to GDP | off or inactive |
| GTP hydrolysis activity | cleave GTP to GDP |
| GTPase Activating protein (GAP) | Promotes GTP hydrolysis |
| Guanine Exchange Factor (GEF) | Promotes release of GDP so GTP can bind |
| Extracellular matrix (ECM) | network of secreted proteins and carbohydrates outside of the lipid bilayer. |
| Collagen | Three polypeptide chains -strong |
| Fibronectin | Large glycoprotein -domains to interact w/ other proteins |
| Laminin | Large glycoprotein- interacts w/ other laminins or ECM molecules |
| ECM Functions | support/structure for cell, cell-cell interactions/ communication, provides protection |
| Transmembrane proteins | connecting inside cell w/ extracellular environment |
| Integrin | cytoskeletal and extracellular interaction |
| Cadherin | cell adhesion proteins binds to cadherins on adjacent cells |
| Epithelia (skin cells) | Cell-cell interactions: tight junctions stitching adjacent cells together. |
| desmosomes | spot welds |
| Gap Junctions | Pores that allow ions and molecules to flow btw cells. |
| Interphase | DNA "loosely" packed. includes G1, S, G2 phases |
| G1 | each chromosome contains a single, double-stranded DNA molecule. Cell contains a single centrosome organizing the microtubule network |
| Centrosome | (microtubule organizing center (MTOC)) group of proteins that organize microtubules |
| Microtubule minus ends are toward | centrosome plus ends away |
| S phase | DNA replicates (forming two sister chromatids= identical DNA molecules), centrosome also duplicates |
| G2 | Each chromosome now contains two identical copies of each chromosome and two centrosomes |
| Mitosis | condensed chromosomal DNA gets equally distributed into daughter cells. Microtubules and associated proteins drive the movement of chromosomes (DNA) |
| After Mitosis | the daughter cells (in G1) have exactly the same DNA as the mother cell had (in G1) |
| Mitosis Prophase | Nuclear envelope begins to break down. Two centrosomes separate mitotic spindle made of microtubules forms btw them. Chromosomes begin condensation and become more tightly wound around histones. |
| Sister Chromatids | identical DNA molecules attached at centromere |
| Centromere | region of DNA bound by proteins that keep sister chromatids together |
| Kinetochore | complex of proteins associated with the centromere |
| cohesions | proteins that keep sister chromatids associated |
| Prometaphase | Nuclear envelope completes breakdown, centrosomes reach opposite poles and mitotic spindle between them. Kinetochore microtubules associate w/ kinetochores. Interpolar microtubules associate w/ microtubules from opposite direction of each cell. |
| Metaphase | chromosomes are moved to metaphase plate (midway between poles) |
| Metaphase checkpoint | pause in mitosis that waits for all chromosomes to attach to mitotic spindle and reach metaphase plate. |
| Anaphase | sister chromatids separate and move toward opposite poles. |
| How are sister chromatids allowed to separate from each other | Loss of cohesion function |
| How do sister chromatids move towards opposite poles of the cell? | Pulled by disassembly of kinetochore microtubules |
| Telophase | Interpolar microtubules push opposite ends of cell apart. Sister chromatids reach opposite poles. DNA decondenses. Chromatin released from microtubules. Nuclear envelope reassembles. Now you have have two separate nuclei each w/ identical DNA content. |
| Cytokinesis | divison |
| Chromosome | 1 DNA molecule and associated proteins Or 2 DNA molecules (sister chromatids) after DNA replication |
| Diploid | two of each ch’some type (“Pair” of chromosomes of each type) = 2N. One ch’some of pair from mother, other ch’some from father |
| Haploid | one of each chromosome type = 1N |
| Homologous chromosomes | chromosomes of the same type |
| Somatic cells | “body” cells -> diploid (2N) |
| Gametes | “sex” cells -> haploid (N) |
| Germ cells | haploid gametes and the diploid cells they are derived from |
| Meiosis | process of generating haploid cells from diploid |
| Germ line | continuous line of cells passed on from generation to generation |
| Meiosis | producing 4 haploid cells from 1 diploid cell |
| Meiosis I (first cell division of meiosis) | separation of homologous chromosomes |
| Meiosis II (2nd cell division of meiosis) | separation of sister chromatids |
| Before Meiosis I | G1->S-> G2 and DNA and centrosomes duplicated. |
| Meiosis Prophase I | - Nuclear envelope breakdown Separation of centrosome pairs and meiotic spindle formation Chromosome condensation Synapsis of homologous chromosomes Proteins link DNA together along entire length of homologous chromosomes |
| Synaptonemal complex | complex of proteins that links homologous ch’somes during synapsis |
| Tetrad | complex of two homologous chromosomes and their sister chromatids in synapsis |
| Homologous recombination (crossing over) | occurs between homologous chromosomes the two homologous chromosomes “break” at the exact same place and swap DNA at that point! Each sister chromatid has some maternal and some paternal DNA!! |
| Meiosis Prometaphase I | paired homologous ch’somes attached to kinetochore microtubules |
| Meiosis Metaphase I | paired homologous chromosomes move to metaphase plate - Crossing over has been completed, but tetrads remain together |
| Meiosis Anaphase I | homologous chromosomes separate toward poles |
| Meiosis Telophase I | chromosomes complete movement toward poles |
| Meiosis Cytokinesis | cytoplasm divided |
| Independent assortment | each chromosome pair sends chromosome from male or female randomly toward opposite poles - end up with mixture of maternal and paternal chromosomes in each daughter cell produced Sister chromatids remain attached to each other |
| At end of Meiosis I: | have two daughter cells Each has one homologous chromosome from each original pair - Each contains a mixture of maternal and paternal DNA -> due to homologous recombination and independent assortment |
| Meiosis II does not have | No DNA duplication |
| Meiosis II Prophase II | meiotic spindle forms and attaches to kinetochores |
| Meiosis II Metaphase II | chromosomes move to metaphase plate |
| Meiosis II Anaphase II | sister chromatids move to opposite poles |
| Meiosis II Telophase II | nuclei reform |
| Meiosis II Cytokinesis | Cytoplasm separate |
| End of Meiosis II: | Four haploid daughter cells DNA content is different in each |
| Spermatogenesis | meiosis and differentiation (cell specialization) to produce sperm cytoplasm divided equally => 4 sperm per meiosis |
| Oogenesis | meiosis and differentiation to produce egg cytoplasm divided asymmetrically -> one egg (oocyte) + three polar body cells |
| Genetic variation | primary reason for the evolution of sexual reproduction |
| Sources of genetic variation: | 1. Homologous recombination (crossing over) 2. Independent assortment (during meiosis) 3. Random fertilization – any sperm could meet any egg! |
| Non-disjunction | failure of homologous chromosomes or sister chromatids to segregate properly - End up with incorrect number of chromosomes in gametes! |
| How can protein activity changes alter what is happening in each “phase” of the cell cycle? | proteins involved were identified by research groups working on model organisms (yeast, amphibians, sea stars) = non-human organisms with characteristics that make them easier to study |
| Cyclin proteins | Proteins “cycled” in abundance during cell cycle |
| G1/S cyclins | most abundant at end of G1 and when cell enters S-phase |
| G2/M cyclins | most abundant at end of G2 and when cell enters mitosis |
| Are cyclins involved in the cell cycle? What do they do? | 1. Cyclin proteins bind to another protein that is important for cell cycle control 2. The binding of cyclin to this 2nd protein activates enzymatic activity in the 2nd protein 3. This other protein can switch additional, specific proteins “on” or “off" |
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