Download Revisit to cell Theory AND Characteristics of Living Things

Bellwork: Friday, November 2nd
If you want two batches of cookies,
not just one what would you do?
Double the recipe of course!
Cell Division is the same way, if you want to
make more cells than what you currently have
you have to Double the 'ingredients' or the
materials needed to make the cell BEFORE you
can make new cells
Revisit to cell Theory AND Characteristics of Living Things
• Remember: • All cells come from preexisting cells
• All organisms grow and change
• Worn­out tissues are repaired or replaced by newly produced cells
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Why do cells divide?
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For Reproduction
To Increase our size­For Growth To Repair old, dead, or malfunctioning cells
To carry on the functions of the body
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• Gene­ segment of DNA that gives instructions for a specific trait (such as eye color)
• Chromosomes­ condensed chromatin, they carry the genetic material that is copied and passed down through the generations
• Nucleus­ Control center of the cell, location of DNA
• Nuclear Envelope­ surrounds the nucleus and protects the DNA
• Sister chromatids­ Indentical copies of chromosomes that are formed during prophase, they are held together by a centromere.
• Centromere­ cell structure that joins two sister chromatids together, helps with the movement of chromosomes during cell division, also aids scientists in identifying and studying chromosomes based on their location (site of attachment) 3
1. What is the basic cycle that a cell must go through in order for an organism to grow and heal?
growth, DNA synthesis, and division
2. What happens if cell growth gets out of control?
abnormal cell growth happens, which often results in cancer 3. What are the four main stages of the cell cycle?
The cell cycle is the regular pattern of growth, DNA synthesis, and division that occurs in eukaryotic cells. The four main stages are gap 1, synthesis, gap 2, and mitosis.
4. Which of the four parts above make up the time frame called ‘interphase’?
Gap 1, synthesis, and gap 2
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5. Why are the periods of time between mitosis and DNA synthesis called gaps? What happens to the cell during these times?
Scientists couldn't see anything happening in the time between mitosis and synthesis originally so they galled them gaps. We now know that during interphase, or these gaps, cells carry out their normal functions and undergo critical growth and preparation for cell division.
6. G 1 is where the cell spends most of its life. What 3 things happen in this stage?
1. carries out its normal functions
2. increases in size
3. organelles increase in number
7. Describe the critical check point that all cells must go through before entering the synthesis stage. Why is this necessary?
The check point is done to prevent your cells from dividing if they are not healthy so that new cells are always healthy (just like your Dr. might prevent you from participating in sports if you are ill). The cells need to have enough nutrition, adequate size, and undamaged DNA to divide successfuly. Beyond this they have to have chemical signals from other cells telling them to divide.
8. What happens in the S­stage of the cell cycle?
In the synthesis or S­stage, Cells make a copy of its nuclear DNA.
9. Compare the G2 stage to the G 1 stage. In G2, the cell continues to carry out its normal functions, just like the G1. More growth of the cells occurs and the cell goes through a second check point to ensure that damaged cells are not duplicating. ­It's like G1 all over again!
10. What are the two processes found in the M­stage of the cell cycle? What happens in each of these two processes?
The two processes are: Mitosis and cytokinesis.
Mitosis: the cell nucleus and its contents divide.
Cytokinesis: The cell's cytoplasm divides.
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11. What is the product of the cell cycle?
The result of the cell cycle is two identical daughter cells that are genetically identical to the original cell.
12. Compare and contrast prokaryote to eukaryote cells. How do these characteristics affect the rate of cell division?
complex cell cycle for cell division
Replicate via binary fission
-make a copy of DNA and split in two
Because prokaryotes do not have the membrane­bound organelles and cytoskeleton found in eukaryotes they tend to divide much faster.
13. How does the rate of cell division differ from young children to adults? Explain.
Cell division is greater in embryos and young cheildren but this is because their bodies are still developing.
14. Do all cells divide at the same rate? Explain.
No, the rate is linked to your bodn'ts need for those cells and the cell rate of division varies from cell type to cell type.
15. What is G 0 and how is it related to cell division?
Cells that rarely divide are thought to enter this stage. In here cells are unlikely to divide but they continue to carry out normal cell functions. they can always get out if they need to divide. Neuron cells are ones that go in here and very rarely ever come out again.
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16. Why is a cell’s size limited to a certain size range? Why can’t they be smaller? Larger?
If the cells were too small they couldn't fit in all of the necessary organelles to help them function properly. (Ex: not enough mitochondria would mean not enough energy to live.)
If the cells were too large, then the ratio of cell surface area to volume would be off. Remember: materials such as oxygen, nutrients and waste must move in and out of the cell. If these materials could not be transported in an adequate amount of time the cell wouldn't function properly. Increasing size the volume increases faster than the surface area and so there is not enough space to move materials.
17. What would happen if a cell was unable to coordinate growth and division?
The cell's size would get out of control. For example: if the cell was more than double its origianl size BEFORE doubleing then the daughter cells would be larger which means every generation the cells would get larger and larger. (The same thing would happen if the cells did not grow enough.)
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