The Cell Cycle

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The Cell Cycle
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Why are cells so small??

• What limits the size of a cell??
• Most cells are between .002 - .2 millimeters

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What limits the size of a cell?

• Diffusion
• Very fast and efficient over short distances
• Becomes slow and inefficient as the distances
  become larger
• Cells would die before nutrients could reach the
  organelles if the cell was too big

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What limits the size of a cell??

• Surface Area to Volume Ratio
• As cell size increases, its volume increases much
  faster than surface area
• Example If cell size doubles, the cell would
  require 8 times more nutrients, but the cell
  membrane would only increase by 4 times. This
  would mean that the cell doesnt have enough room
  (cell membrane) to diffuse.

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What limits the size of a cell??

• DNA
• Theres a limit to how fast DNA can make proteins
• If you have a large cell than the DNA cant make
  proteins fast enough for the cell.

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The Cell Cycle

• Cell Reproduction
• One cell (parent cell) reproduces to make 2
  identical cells (daughter cells)
• 5 steps in this process

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What is Mitosis

• Mitosis isTHE PROCESS BY WHICH A CELLS NUCLEUS
  DIVIDES!

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Mitosis

• Interphase
• This phase is broken down into 3 subphases
• G1 Cell grows in size
• S DNA duplicates itself
• Chromatin duplicates long coily strands of DNA
  that become wrapped up
• G2 Rapid Growth before dividing
• Cells spend most of their time in this phase

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Interphase
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Interphase
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Interphase
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Interphase
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Mitosis

• Prophase
• A.) Chromatin organizes itself into chromosomes
  made up of 2 sister chromatids attached by a
  centromere
• Sister Chromatids A chromosome and its
• duplicated twin
• Centromere rubber band structure that
• joins the 2 sister chromatids together

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Prophase

• B.) Nuclear membrane breaks down
• Nucleus dissolves
• C.) Centrioles move to opposite ends of the cell
  (poles)
• Centrioles cylinder structures that will reel
  in the chromatids
• D.) Spindle fibers form
• Spindle fibers football shaped set of ropes
  that will attach to the centrioles and the
  chromatids

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Prophase
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Prophase
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Prophase
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Prophase
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Prophase
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Prophase
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Prophase
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Mitosis

• Metaphase
• Spindle fibers attach to centrioles and sister
  chromatids at their centromeres.
• Chromosomes line up in the middle of the cell

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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Metaphase
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Mitosis

• Anaphase
• The centromeres split apart and the sister
  chromatids separate from each other
• The spindle fibers pull the chromatids toward the
  poles

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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Anaphase
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Mitosis

• Telophase
• Chromatids reach the poles
• Chromosomes unwind
• Spindle fibers break down
• Nucleus reforms
• Cell begins to split
• Cleavage furrow

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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Telophase
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Mitosis

• Cytokinesis
• Cells Separate

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Cytokinesis
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The Cell Cycle