1. The Cell Cycle/Mitosis

2. How do little elephants grow up to be big elephants?
CELL GROWTH AND DIVISION!

3. Why do cells divide?
Three reasons why cells reproduce by asexual reproduction: Growth Repair Replacement

4. When do cells divide?
Most limiting factor in size is the surface area of the cell membrane.
Cells must obtain nutrients
As volume increases, cell surface area does not increase as greatly
Larger cells require a larger surface area for survival

5. Surface Area & Volume
The rate at which nutrients enter a cell depends on the surface area of the cell.
Surface Area of Cell = Total area of its cell membrane
The rate at which nutrients are used up in a cell depends on the volume of the cell.
Volume of a Cell = Total amount of space inside the cell
Small cells have a larger amount of surface area compared to volume.
An increase in surface area allows for more nutrients to pass into the cell and wastes to exit the cell more efficiently

6. Surface Area to Volume Ratio
A ratio is a measure of the relative size of 2 quantities. Example: ½ or 1:2
Surface Area= (l) x (w) x (# of sides)
Volume = (l) x (w) x (h)
Cells want a large surface area compared to a small volume.

7. The cell cycle is the series of events that cells go through as they grow and divide.
Interphase is the period of growth that occurs between cell divisions.

8. During the cell cycle: a cell grows prepares for division
divides to form two daughter cells, each of which begins the cycle again

9. The cell cycle consists of four phases:
G1 (First Gap Phase)
S Phase
G2 (Second Gap Phase)
M Phase

10. Events of the Cell Cycle
During G1, the cell:
increases in size
synthesizes new proteins and organelles
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11. Events of the Cell Cycle
During the S phase:
chromosomes are replicated
DNA synthesis takes place
Once a cell enters the S phase, it usually completes the rest of the cell cycle.
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12. Events of the Cell Cycle
The G2 Phase (Second Gap Phase):
organelles and molecules required for cell division are produced
Once G2 is complete, the cell is ready to start the M phase—Mitosis
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13. Mitosis

14. In eukaryotes, cell division occurs in two major stages:
The first stage, division of the cell nucleus, is called mitosis.
The second stage, division of the cell cytoplasm, is called cytokinesis.

15. Chromosomes
Genetic information is passed from one generation to the next on chromosomes.
Before cell division, each chromosome is duplicated, or copied.

17. Each chromosome consists of two identical “sister” chromatids.
Each pair of chromatids is attached at an area called the centromere.
Sister chromatids
Centromere

18. When the cell divides, the chromatids separate.
Each new cell gets one chromatid.

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Mitosis
Biologists divide the events of mitosis into four phases: (PMAT)
Prophase
Metaphase
Anaphase
Telophase
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Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
Mitosis
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21. Chromosomes (paired chromatids)
Section 10-2
Spindle forming
Prophase
Prophase
Chromosomes (paired chromatids)
Centromere
Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
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Prophase = Preparation Phase
Prophase is the first and longest phase of mitosis.
The centrioles separate and take up positions on opposite sides of the nucleus.
Spindle
forming
Centromere
Chromosomes
(paired chromatids)
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Spindle
forming
The centrioles lie in a region called the centrosome The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.
Centromere
Chromosomes
(paired chromatids)
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Spindle
forming
Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down.
Centromere
Chromosomes
(paired chromatids)
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Metaphase
Centriole
Spindle
Centriole
Metaphase
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Metaphase = Middle
The second phase of mitosis is metaphase.
The chromosomes line up across the center of the cell.
Microtubules connect the centromere of each chromosome to the poles of the spindle.
Centriole
Spindle
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27. Individual chromosomes
Anaphase
Individual chromosomes
Anaphase
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Anaphase = Apart Phase
Anaphase is the third phase of mitosis.
The sister chromatids separate into individual chromosomes.
The chromosomes continue to move until they have separated into two groups.
Individual
chromosomes
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29. Nuclear envelope reforming
Telophase
Nuclear envelope reforming
Telophase
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Telophase = Two Phase
Telophase is the fourth and final phase of mitosis.
Chromosomes gather at opposite ends of the cell and lose their distinct shape.
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A new nuclear envelope forms around each cluster of chromosomes.
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Cytokinesis
Cytokinesis
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Cytokinesis
During cytokinesis, the cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes
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34. Cytokinesis Division of the cytoplasm.
Animal Cells: Cell Membrane drawn inward.
Plant Cells:
formation of
cell plate

35. Cancer Cancer = Uncontrolled Cell Growth.
The cell does not respond to external/internal stimuli.
When Cells divide uncontrollably, a tumor can result.
Causes of cancer include: smoking, radiation, infection, genetics.

36. Regulating the Cell Cycle
Cyclins: proteins that regulate the timing of the cell cycle in eukaryotic cells.
2 Types of Regulatory Proteins:
Internal Regulators: proteins that respond to events inside the cell.
External regulators: proteins that respond to events outside the cell.

37. Cell Facts
50,000 of the cells in your body will die and be replaced with new cells, all while you have been reading this sentence!
It takes about 8 hours for one of your cells to completely copy its DNA.
One single cell contains two meters of DNA.