Plant Cell Part 3 PDF

‫‪Plant cell PART 3‬‬ ‫املصدر‪ /‬الكتاب الجامعي‬  Plant cell Organelles: ✓ Lysosomes: which digest organic compounds. ✓ NOTE : many plant cells acc...

‫‪Plant cell PART 3‬‬ ‫املصدر‪ /‬الكتاب الجامعي‬  Plant cell Organelles: ✓ Lysosomes: which digest organic compounds. ✓ NOTE : many plant cells accumulate lipids as oil ✓ There are many other parts of the eukaryotic cell. drops located directly in cytoplasm. ✓ nucleus : membrane bound structure that present ✓ Cellular Skeleton: is a collection of protein only in eukryotic cells. filaments within the cytoplasm. ✓ function : store DNA or hereditary information. ✓ Microtubules: are key organelles in cell division, A. Nucleolus: it manufacutures ribosomes they form the basis for cilia & flagella. B. Nucleopore : Membrane is perforated with holes ✓ are guides for the construction of the cell wall. that allow proteins & nucleics acids to pass through. ✓ Ribosomes:(protein factory) , smallest non membranous organelle which comprise RNA & Proteins , help to synthesize proteins. ✓ The rough endoplasmic reticulum (RER):Has ribosomes along its surface. ✓ Golgi apparatus: is made up of sacs which are flattened &stacked , it modifies , packages & sorts proteins & CHO ; not essential component of cell. ✓ Peroxisomes: which help in photosynthesis.  Plant cell Mitosis & the Cell Cycle: The Cell Cycle: ✓ Mitosis is a process of nuclear division in which ✓ Interphase : The period when the nucleus is chromosomes divide, separate, & form 2 identical between divisions. nuclei. ✓ It is a period of replication of organelles, followed ✓ Mitosis in plants involves the formation of a new by chromosomes are duplicated, then spindle cell wall between the 2 identical nuclei. fibers (bundles of microtubules) are made. ✓ In plants, good sites to observe mitosis are in root ✓ Cell cycle = Interphase + the 4 phases of mitosis. , shoot apices, & newly developing leaves. ✓ Mitosis does not change the cells genotype. the Phases of Mitosis: target of mitosis is to distribute genetic material equally. ✓ Karykinesis : splitting of nucleus , ✓ Prophase: The first stage,& its the longest. ✓ cytokinesis : splitting of whole cell. ✓ nucleus disintegrates. ✓ All prokaryota (monera) have simple division ✓ the DNA is super spiralized into chromosomes. called binaryfission :DNA replicate , segregate & ✓ The chromosomes become visible as long threads. then splits into two. ✓ On each strand is a small body called a ✓ Eukaryotics have much more DNA the centromere. prokryotics , this is why their division is more ✓ the chromosomes start to shorten & thicken. complicated.  Plant cell ✓ Metaphase: The nuclear membrane and nucleolus can no be seen. ✓ Metaphase is marked by the appearance of the spindle. ✓ The chromosomes migrate to the equator & held together at the centromeres. ✓ Anaphase: microtubules moves chromatides ( I like) moving to opposite poles of the cell. ✓ Telophase: The chromatid completing their movement to the poles. ✓ It ends with a new nuclear membrane forms around each group of chromatids and nucleoli reappears. ✓ Plant cells use vesicles to form border , whereas many protists & animals form a constriction which finally separate two cells. ✓ Most important stage of the cell cycle is synthetic stage (s-stage) when every DNA is duplicated I --- X.  Plant cell ✓ cytokinesis involves the formation of a phragmoplast made up of short microtubules aligned parallel to the spindle microtubules. ✓ The phragmoplast forms in the center of the cell. ✓ Phragmoplast microtubules trap dictyosome vesicles that fuse into a large, flat, plate-like vesicle in which two new primary walls & amiddle lamella begin to form. ✓ The phragmoplast then grows outward toward the walls of the original cell. ✓ The new walls meet & fuse with the wall of the mother cell, completing the division of the mother cell into two daughter cells.  Plant cell MEIOSIS (Reductional division ) IN PLANT CELL: 3. at the time of zygote formation. Note : each meiotic division is divided into same four ✓ is a process of cell division of the reproductive stages as in mitosis : prophase , metaphase , cells of both plants &animals in which the diploid anaphase & teliphase & the name of the stage is number is reduced to haploid. followed by I OR II , depending on which divsion of ✓ It takes places during gamets formation. the cycle is involved. ✓ Meiosis consist of two complete divisions First (heterotypic) & second (homotypic). ✓ Diploids cell produces four haploid cells. SIGNIFICANCE OF MEIOSIS: ✓ The first , number of chromosomes is reduced to ✓ The occurrence of crossing over results in half & the second is mitosis ( equaterial ). recombination of genes. ✓ During sexual reproduction , the two gamets male ✓ The recombination of genes results in genetic & female each having single set of chromosomes variation. (n) fuse to form zygote. ✓ The genetic variation form raw materials for ✓ The zygote thus contain twice (n+n=2n). one set evolution. from male & the other set from female. ✓ Meiosis take place in plants during any one of the following events: 1. at the time of spore formation. 2. at the time of gamets formation.