Chapter 10 Cell Growth

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Chapter 10Cell Growth Division

• Section 101Cell Growth

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Objectives

• What problems does growth cause for cells?

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Limits To Cell Growth

• Key Concept
• The Larger A Cell Becomes, The More Demands The
  Cell Places On Its DNA And The More Trouble The
  Cell Has Moving Enough Nutrients And Waste Across
  The Cell Membrane

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DNA Overload

• Extra Copies Of DNA Are Not Made
• Like A Small Town Infrastructure Needs To Grow
  As The Town Grows

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DNA Overload
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Exchanging Materials

• Cell Membrane (Surface Area)
• Nutrients Enter
• Waste And Products Leave
• The Amounts Of Nutrients Needed And The Amount Of
  Waste Produced
• Depends On The Cells Volume

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Ratio of Surface Area To Volume

• As Cell Size Increases
• Volume Increases More Rapidly Than Surface Area
  (cell membrane)
• Cell Membrane Can Not Cycle Nutrients and Wastes
  Fast Enough.

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Cell Division

• Cells Divide
• Before They Become
• To Large
• Cell Division Is The Process By Which A Cell
  Divides Into Two Daughter Cells

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Cell Division

• Before A Cell Divides
• It Replicates Its DNA
• So Each Cell Has
• An Exact Copy

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Chapter 10Cell Growth Division

• 10-2 Cell Division

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Objectives

• What are the main events of the cell cycle?
• What are the four phases of mitosis?

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Chromosomes

• Carry Genetic Information From One Generation of
  Cell to the Next Generation of Cells
• Made Up Of
• DNA Protein

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Chromosomes

• Every Organism Has A Specific Number Of
  Chromosomes
• Fruit Flys 8
• Carrots 18
• Humans 46
• Giraffe 30
• King Crab 208

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Chromosomes

• Not Visible Except During Division
• Well Before Division They Duplicate

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Chromosomes

• Chromatids
• Just Before Division Chromosomes Condense Into
  Compact, Visible Structures Called Chromatids
• Centromere
• Each Chromosome Has Two, Identical Chromatids
  Connected By A Centromere

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Chromosomes
Chromatid A
Copy of Chromatid A
Centromere
Kenitophore
Microtubules or Spindle Fibers
Copy of Chromatid A
Chromatid A
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The Cell Cycle

• Key Concept
• During The Cell Cycle
• A Cell Grows
• Prepares For Division
• Divides To Form Two Daughter Cells
• Each Daughter Cell Then Begins The Cycle Again

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Cell Cycle
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Interphase

• Time In-Between Cell Divisions

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Cell Division or M phase
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Events Of The Cell Cycle

• Interphase
• May Be Quite Long
• Divided Into 3 Parts

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The 3 Parts of Interphase

• G1 Phase
• Cell Grows In Size
• Synthesize New Proteins Organelles

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The 3 Parts of Interphase

• S Phase
• Chromosomes Are Replicated
• Once This Phase Begins The Cell Completes Division

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The 3 Parts of Interphase

• G2 Phase
• Organelles Proteins Required For Mitosis Are
  Produced
• Cell Is Now Ready To Enter
• M Phase (Mitosis)

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Mitosis

• Key Concept
• Biologists Divide The Events Of Mitosis Into Four
  Phases
• Prophase
• Metaphase
• Anaphase
• Telophase

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Prophase

• 1st Longest
• Phase
• Chromosomes Become Visible
• Centrioles Separate Take Up Position On
  Opposite Sides Of The Nucleus
• Spindle Begins To Form

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Prophase

• In Animals
• Spindle Fibers Attach To Centromere On Each
  Chromatid
• In Plants
• No Centromere, Spindle Fibers Still Form From
  Centrosomes

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Late Prophase

• Nucleolus Disappears
• Nuclear Envelope Breaks Down

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Metaphase

• Short
• Just A Few Minutes
• Chromosomes Line Up Across Center Of The Cell
• Microtubules Connect The Centromere To The Poles
  Of The Spindle

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Anaphase

• Centromeres Separate
• Sister Chromatids Separate
• Each Set Of Chromosomes Pulled To Their Poles

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Telophase

• Chromosomes Disperse
• New Nuclear Envelopes Form
• Spindle Breaks Apart
• Nucleolus Reforms

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Cytokinesis

• There Are Now Two Nuclei In One Cell
• Cytokinesis Is The Division Of The Cytoplasm Into
  Two Cells
• The Cell Membrane Is Drawn Inward Until The Cell
  Pinches Into Two Equal Parts

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Cytokinesis In Plants

• A New Cell Plate Forms In The Middle Of The Cell
  Which Attaches To, And Becomes Part Of, The Cell
  Wall

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Chapter 10Cell Growth Division

• Section 10-3
• Regulating Cell Growth

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Objectives

• How is the cell cycle regulated?
• How are cancer cells different from other cells?

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Controls On Cell Division

• When Cells In Cell Cultures Come In Contact With
  Each Other, They Stop Growing.
• Why?

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Controls On Cell Division

• If A Hole Is Made In The Cell Culture, Cell
  Growth Will Restart Continue Until The Hole Is
  Filled.
• Why?

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Controls On Cell Division

• In Your Body The Rate Of Cell Growth Is
  Controlled.
• Injury Causes Rapid Division Until The Wound Is
  Healed. Then Division Slows Again.
• Why?

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Cell Cycle Regulators

• Key Concept
• Cyclins Regulate The Timing Of The Cell Cycle In
  Eukaryote Cells.
• Discovered In The 1980s
• Cyclins Are A Family Of Closely Related Proteins
  That Rise Fall Within The Cell With The Cell
  Cycle

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Cyclins Cell Cycle
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Cell Cycle Regulators

• Cyclins
• When Injected Into Non-Dividing Cells, Cyclins
  Cause Mitotic Spindles To Form.

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Cell Cycle Regulators

• Cyclins
• When Injected Into Non-Dividing Cells, Cyclins
  Cause Mitotic Spindles To Form.

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Cell Cycle Regulators

• Cyclins
• When Injected Into Non-Dividing Cells, Cyclins
  Cause Mitotic Spindles To Form.

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Cell Cycle Regulators

• Other Regulator Proteins Continue To Be Found.

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Other Internal Regulators

• These Proteins Respond To Events Inside The Cell.
• Several Make Sure The Cell Does Not Enter Mitosis
  Until All Chromosomes Have Been Replicated.
• Others Stop The Cell From Entering Anaphase Until
  All Chromosomes Are Attached To The Mitotic
  Spindle

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Cyclins Cell Cycle
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External Regulators

• These Respond To Events Outside The Cell
• They Direct The Cell To Speed Up Or Slow Down The
  Cell Cycle
• These Include Growth Factors

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Growth Factors

• Very Active During
• Embryonic Development
• Wound Healing

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Other External Regulators

• Molecules On The Cell Membrane Of Neighboring
  Cells Slow The Growth Process
• They are like sensors that signal the cell to
  slow/stop growth

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Uncontrolled Cell Growth
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Uncontrolled Cell Growth

• Key Concept
• Cancer Cells Do Not Respond To The Signals That
  Regulate The Growth Of Most Cells. As A Result,
  They Form Masses Of Cells Called Tumors That Can
  Damage Surrounding Tissue.

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Uncontrolled Cell Growth

• Metastasis
• Cancer Cells Break Loose From The Tumor And
  Invade Tissues Throughout The Body

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Some Carcinogen Sources

• Smoking
• Radiation
• Viral Infection

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p53 Gene

• Usually Stops The Cell Cycle Until Chromosomes
  Have Been Properly Replicated.
• High Percentage Of Cancers Cells Have Defects At
  This Gene Site