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The Plant Cell Cycle

The Plant Cell Cycle. Chapter 3. Nucleus DNA Replication Cytoskeleton. The plant cell. Cell wall. CHLOROPLAST. CHLOROPLAST. Plasma membrane. MITOCHONDRIUM. NUCLEUS. MITOCHONDRIUM. MITOCHONDRIUM. CYTOSOL. CHLOROPLAST. CHLOROPLAST. MITOCHONDRIUM.

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The Plant Cell Cycle

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  1. The Plant Cell Cycle Chapter 3

  2. Nucleus • DNA • Replication • Cytoskeleton

  3. The plant cell Cell wall CHLOROPLAST CHLOROPLAST Plasma membrane MITOCHONDRIUM NUCLEUS MITOCHONDRIUM MITOCHONDRIUM CYTOSOL CHLOROPLAST CHLOROPLAST MITOCHONDRIUM Notes: 1) cytosol is the same as cytoplasm 2) not all of the plant cell structures and organelles are shown

  4. one pore • Nucleus • Ovoid or irregular shaped • Surrounded by double membrane (nuclear envelope) nuclear envelope 1 µm 0.2 µm lipid bilayer facing the nucleoplasm lipid bilayer facing the cytoplasm nuclear envelope pore complex that spans both bilayers Fig. 3-8, p. 37

  5. Structure of Phospholipids and Glycolipids • Hydrophilic • Hydrophobic

  6. Structure of Phospholipids and Glycolipids

  7. Central dogma of Molecular Biology DNA TRANSCRIPTION REPLICATION RNA + TRANSLATION mRNA Ribosome protein

  8. Nucleolus: production center for ribosomes nuclear envelope Nucleolus (rDNA, rRNA, ribosomal proteins, etc…) Chromosome Early Prophase cell

  9. Structure of DNA

  10. A nucleosome consists of part of a DNA molecule looped twice around a core of histones (chromosomal proteins). core of histone molecules Fig. 3-9a, p. 37

  11. Immerse a chromosome in saltwater and it loosens up to a beads-on-a-string organization. The “string” is one DNA molecule. Each “bead” is a nucleosome. Fig. 3-9b, p. 37

  12. At a deeper level of structural organization, the chromosomal proteins and DNA are organized as a cylindrical fiber (again a helical structure). Fig. 3-9c, p. 37

  13. At times when a chromosome is most condensed (during Mitosis), the chromosomal proteins interact, which packages loops of already coiled DNA into a “supercoiled” array (two additional helical organizations). Such a tightly packaged DNA molecule is more easily moved around compared to when it would be a long “loose” thread (important during cell division) Fig. 3-9d, p. 37

  14. old new new old Fig. 2-18, p. 26

  15. Cytoskeleton • Structures in cytoskeleton • Microtubules • Motor proteins • Microfilaments • Specialized proteins connect microtubules and microfilaments to other organelles • Connections thought to coordinate many cell processes

  16. Cell Cycle

  17. some cells leave the cycle pre-DNA synthetic phase or gap phase G1 cytokinesis telophase CELL DNA synthesis phase anaphase Mitosis (M) Interphase metaphase S CYCLE prophase G2 some cells leave the cycle premitosis phase Note: Interphase includes G1, S and G2 phases Fig. 3-15, p. 43

  18. Principal Control Point Hypothesis control point G1 M S control point G2 Fig. 3-16, p. 44

  19. A B C band of microtubules microtubules nucleus cell wall cytoplasm Fig. 3-18, p. 45 Formation of the preprophase band of microtubules in meristematic cells: A) Section at right angles to the plane of the future cell plate shows a cross section of microtubules. B) Section in the plane of the future cell plate shows microtubules encircling the nucleus. C) Three-dimensional drawing of A and B.

  20. Mitosis • Four phases • Prophase • Metaphase • Anaphase • Telophase

  21. Mitosis d c e a b cell plate nuclear envelope pole spindle fiber nucleolus chromosome kinetochore Early Prophase Late Prophase Metaphase Late anaphase Telophase Fig. 3-19, p. 46

  22. The roles of microtubules in mitosis Fig. 3-17, p. 45 Visualization of tubulin (component of microtubules) during mitosis.

  23. Cell division in Plants versus Animals • Animal cells do not have a cell wall Because plant cells have cell walls, the direction of cell division is a major determinant of overall plant development (cells are caught in a rigid structure and cannot reorganize after cell division has been completed). The direction/orientation of cell division is controlled by plant hormones.

  24. Cell division in Plants versus Animals • Animal cells do not form a preprophase band (PPB) • During Telophase: - in plants: a cell plate is formed at the start of cytokinesis (direction of cell plate formation depends on hormone action via effects on PPB formation) - in animals: the cell pinches in the middle to form two cells, no cell plate is formed.

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