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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
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)
the nucleolus
The Nucleolus
  • A non-membrane bound structure and is the center of the cell composed of proteins and nucleic acids.
the nucleolus1
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.
  • Found inside of the nucleus
  • No big organelles
  • Holds the chromatin and nucleolus
during cell division
During Cell Division
  • When the nuclear membrane disappears, so does the nucleoplasm.
  • When the cell nucleus has reformed, the nucleoplasm fills the space again.
  • 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”.
  • The uncoiled form of chromosomes
  • Just before reproduction, chromatin condenses to form chromosomes.
number of chromosomes
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.
what do chromosomes do
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
diploid cells
Diploid Cells
  • Cells with two complete sets of chromosomes
  • Cells with only one set of chromosomes
  • Found in cells involved in sexual reproduction
  • Created in meiosis
  • Help with cell division (both mitosis and meiosis)
  • Cannot be seen when the cell is not dividing
  • Made of microtubules
centriole structure
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
  • 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).
one of their jobs cell division
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.
between cell divisions
Between Cell Divisions
  • Cannot see centrioles
  • Instead You will see a condensed and darker area called the centrosome.
centrioles job during cell division
Centrioles Job During Cell Division
  • Interphase - the cell is at rest until the thecentrioles duplicate.

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


Telophase - Chromosomes begin to unravel and new nuclear envelopes begin to appear.

  • The centrioles have done their job.