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Bell Work

Bell Work. What does each of the following cell parts do? When compared to a factory, what would be there job? Nucleus Cell Membrane Cell Wall Cytoplasm ( cytosol ). Intro to Biology – Lecture 40. Inside the Nucleus. Inside the Nucleus. The Nucleolus.

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Bell Work

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  1. Bell Work • What does each of the following cell parts do? • When compared to a factory, what would be there job? • Nucleus • Cell Membrane • Cell Wall • Cytoplasm (cytosol)

  2. Intro to Biology – Lecture 40 Inside the Nucleus

  3. Inside the Nucleus

  4. The Nucleolus • A non-membrane bound structure and is the center of the cell composed of proteins and nucleic acids.

  5. The Nucleolus • Its function is to transcribe ribosomal RNA (rRNA) and assemble it within the cell. • It takes up to about 25% of the nuclear volume.

  6. Nucleoplasm • Found inside of the nucleus • No big organelles • Holds the chromatin and nucleolus

  7. During Cell Division • When the nuclear membrane disappears, so does the nucleoplasm. • When the cell nucleus has reformed, the nucleoplasm fills the space again.

  8. Chromosomes • Carry all of the information used to help a cell grow, thrive, and reproduce. • Made of DNA • Segments of DNA in specific patterns are called genes. • In a factory, chromosomes would be the “record books”.

  9. Chromatin • The uncoiled form of chromosomes • Just before reproduction, chromatin condenses to form chromosomes.

  10. Number of Chromosomes • Humanshave 46 chromosomes (23 pairs). • Peas only have 12. A dog has 78. • There is a crayfish with 200 chromosomes. • The number of chromosomes is NOT related to the intelligence or complexity of the creature.

  11. What do Chromosomes do? • Chromosomes work with nucleic acids in the cell to build proteins and help in cell division. • mRNA in the nucleus with the DNA • tRNA is found outside of the nucleus in the cytosol

  12. Diploid Cells • Cells with two complete sets of chromosomes

  13. Haploids • Cells with only one set of chromosomes • Found in cells involved in sexual reproduction • Created in meiosis

  14. Centrioles • Help with cell division (both mitosis and meiosis) • Cannot be seen when the cell is not dividing • Made of microtubules

  15. Centriole Structure • a small set of microtubules arranged in a specific way • Found in pairs and move towards opposite ends of the nucleus when it is time for cell division • During division, threads (called the mitotic spindle) are attached to the centrioles

  16. Microtubules • Thick Protein Tubes • Strong spirals of thousands of subunits • Subunits are made of the protein tubulin • They are like the secretaries of the factory. They have many small jobs dealing in the nucleus (command center).

  17. One of their Jobs – Cell Division • They connect to chromosomes, help them with their first split, and then move to each new daughter cell. • Once the cell has finished dividing, the microtubules are put to work in other places.

  18. Between Cell Divisions • Cannot see centrioles • Instead You will see a condensed and darker area called the centrosome.

  19. Centrioles Job During Cell Division • Interphase - the cell is at rest until the thecentrioles duplicate.

  20. Prophase - centrioles move to opposite ends of the nucleus and a mitotic spindle of threads begins to appear.

  21. Metaphase - Threads connect to the chromosomes.

  22. Anaphase - Chromosomes are split and pulled towards each centriole.

  23. Telophase - Chromosomes begin to unravel and new nuclear envelopes begin to appear. • The centrioles have done their job.

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