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Organelle/Macromolec ule Main function Structure Organisms carboxysome carbon fixation protein-shell compartment some bacteria chlorosome photosynthesis light harvesting complex green sulfur bacteria flagellum movement in external medium protein filament some prokaryotes and eukaryotes magnetosome magnetic orientation inorganic crystal, lipid membrane magnetotactic bacteria nucleoid DNA maintenance, transcription to RNA DNA-protein prokaryotes plasmid DNA exchange circular DNA some bacteria ribosome translation of RNA into proteins RNA-protein eukaryotes, prokaryotes thylakoid photosynthesis photosystem proteins and pigments mostly cyanobacteria Organelle Main function chloroplast (plastid) photosynthesis endoplasmic reticulum translation and folding of new proteins (rough endoplasmic reticulum), expression of lipids (smooth E.R.) Golgi apparatus sorting and modification of proteins Structure Organisms double-membrane compartment plants, protists (rare kleptoplastic organisms) single-membrane compartment rough E.R. is covered with ribosomes, has folds that are all eukaryotes flat sacs; smooth E.R. has folds that are tubular single-membrane compartment cis-face (convex) nearest to rough endoplasmic reticulum; all eukaryotes trans-face (concave) farthest from rough E.R. mitochondrion energy production double-membrane compartment most eukaryotes vacuole storage, homeostasis single-membrane compartment eukaryotes nucleus DNA maintenance, RNA transcription double-membrane compartment all eukaryotes Notes has some DNA; theorized to be engulfed by the ancestral eukaryotic cell (endosymbiosis) has bulk of genome Minor eukaryotic organelles and cell components Organelle/Macromol ecule Main function Structure Organisms acrosome helps spermatozoa fuse with ovum single-membrane compartment many animals autophagosome vesicle which sequesters cytoplasmic material and organelles for degradation double-membrane compartment all eukaryotic cells centriole anchor for cytoskeleton Microtubule protein animals green algae and other unicellular photosynthetic organisms such as euglenids eyespot apparatus detects light, allowing phototaxis to take place glyoxysome conversion of fat into sugars single-membrane compartment plants hydrogenosome energy & hydrogen production double-membrane compartment a few unicellular eukaryotes lysosome breakdown of large molecules (e.g., proteins + polysaccharides) single-membrane compartment most eukaryotes melanosome pigment storage single-membrane compartment animals muscular contraction bundled filaments not characterized not characterized breakdown of metabolic hydrogen single-membrane compartment peroxide animals fungi myofibril parenthesome peroxisome vesicle material transport single-membrane compartment all eukaryotes all eukaryotes State quiescent/ senescent Interphase Cell division Phase Abbreviation Description G0 A resting phase where the cell has left the cycle and has stopped dividing. Gap 1 G1 Cells increase in size in Gap 1. The G1 checkpoint control mechanism ensures that everything is ready for DNA synthesis. Synthesis S DNA replication occurs during this phase. Gap 0 Gap 2 G2 Mitosis M During the gap between DNA synthesis and mitosis, the cell will continue to grow. The G2 checkpoint control mechanism ensures that everything is ready to enter the M (mitosis) phase and divide. Cell growth stops at this stage and cellular energy is focused on the orderly division into two daughter cells. A checkpoint in the middle of mitosis (Metaphase Checkpoint) ensures that the cell is ready to complete cell division. Mitosis (M Phase) The relatively brief M phase consists of nuclear division (karyokinesis). The M phase has been broken down into several distinct phases, sequentially known as: prophase, metaphase, anaphase, telophase cytokinesis Prophase: The two round objects above the nucleus are the centrosomes. The chromatin has condensed. Prometaphase: The nuclear membrane has degraded, and microtubules have invaded the nuclear space. These microtubules can attach to kinetochores or they can interact with opposing microtubules. Metaphase: The chromosomes have aligned at the metaphase plate. Early anaphase: Kinetochore microtubules shorten. Telophase: The decondensing chromosomes are surrounded by nuclear membranes. Note cytokinesis has already begun, the pinching is known as the cleavage furrow. Cytokinesis “from the greek cyto- (cell) and kinesis (motion, movement)” Cytokinesis is final part of telophase; however, cytokinesis is a separate process that begins at the same time as telophase. Cytokinesis is a separate process, necessary for completing cell division. In both animal and plant cells, cell division is also driven by vesicles derived from the Golgi apparatus, which move along microtubules to the middle of the cell. is the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two, to ensure that chromosome number is maintained from one generation to the next. The end of cytokinesis marks the end of the M-phase. http://www.johnkyrk.com/meiosis.html Interphase: Before meiosis begins, genetic material is duplicated. First division of meiosis Prophase 1: Duplicated chromatin condenses. Each chromosome consists of two, closely associated sister chromatids. Crossing-over can occur during the latter part of this stage. Metaphase 1: Homologous chromosomes align at the equatorial plate. Anaphase 1: Homologous pairs separate with sister chromatids remaining together. Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair. Second division of meiosis: Gamete formation Prophase 2: DNA does not replicate. Metaphase 2: Chromosomes align at the equatorial plate. Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole. Telophase 2: Cell division is complete. Four haploid daughter cells are obtained. Meiosis I •Prophase I – • The chromosomes condense and become visible •The centrioles form and move toward the poles •The nuclear membrane begins to dissolve •The homologs pair up, forming a tetrad . • Each tetrad is comprised of four chromotids - the two homologs, each with their sister chromatid •Homologous chromosomes will swap genetic material in a process known as crossing over. •Genetic material from the homologous chromosomes is randomly swapped •This creates four unique chromatids •Since each chromatid is unique, the overall genetic diversity of the gametes is greatly increased •Metaphase I Microtubules grow from the centrioles and attach to the centromeres •The tetrads line up along the cell equator Compare Metaphase I to Metaphase II and to the Metaphase stage of mitosis. •Anaphase I The centromeres break and homologous chromosomes separate (note that the sister chromatids are still attached) •Cytokinesis begins Compare Anaphase I to Anaphase II and to the Anaphase stage of mitosis. Telophase I •The chromosomes may decondense (depends on species) •Cytokinesis reaches completion, creating two haploid daughter cells Compare Telophase I to Telophase II and to the Telophase stage of mitosis. Meiosis II •Prophase II Centrioles form and move toward the poles •The nuclear membrane dissolves Compare Prophase II to Prophase I and to the Prophase stage of mitosis. Metaphase II •Microtubules grow from the centrioles and attach to the centromeres •The sister chromatids line up along the cell equator Compare Metaphase II to Metaphase I and to the Metaphase stage of mitosis. •Anaphase II The centromeres break and sister chromatids separate •Cytokinesis begins Compare Anaphase Telophase II •The chromosomes may decondense (depends on species) •Cytokinesis reaches completion, creating four haploid daughter cells Compare Telophase II to Telophase I and to the Telophase stage of mitosis. A Comparison between Mitosis and Meiosis