Transcript Section 10–1 Cell Growth

Chapter 10
Cell Growth & Division
Section 10–1
Cell Growth
Objectives

What problems does growth cause for
cells?
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
DNA Overload


Extra Copies Of DNA Are Not Made
Like A Small Town – Infrastructure Needs
To Grow As The Town Grows
DNA Overload
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

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.
Cell Division
Cells Divide
Before They Become
To Large
Cell Division Is The Process By Which A
Cell Divides Into Two Daughter Cells
Cell Division
Before A Cell Divides
It Replicates Its DNA
So Each Cell Has
An Exact Copy
Chapter 10
Cell Growth & Division
10-2 Cell Division
Objectives


What are the main events of the cell
cycle?
What are the four phases of mitosis?
Chromosomes


Carry Genetic Information From One
Generation of Cell to the Next Generation
of Cells
Made Up Of:
DNA + Protein
Chromosomes
Every Organism Has A Specific
Number Of Chromosomes
Fruit Flys = 8
Carrots = 18
Humans = 46
Giraffe
= 30
King Crab = 208
Chromosomes


Not Visible Except During Division
Well Before Division They Duplicate
Chromosomes

Chromatids


Just Before Division Chromosomes Condense
Into Compact, Visible Structures Called
Chromatids
Centromere

Each Chromosome Has Two, Identical
Chromatids Connected By A Centromere
Chromosomes
Chromatid A
Kenitophore
Copy of Chromatid A
Centromere
Microtubules
or
Spindle Fibers
Chromatid A
Copy of Chromatid A
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
Cell Cycle
Interphase
Time In-Between
Cell Divisions
Cell Division or M phase
Events Of The Cell Cycle
Interphase
May Be Quite Long
Divided Into 3 Parts
The 3 Parts of Interphase
G1 Phase
Cell Grows In Size
Synthesize New Proteins &
Organelles
The 3 Parts of Interphase
S Phase
Chromosomes Are Replicated
Once This Phase Begins The
Cell Completes Division
The 3 Parts of Interphase
G2 Phase
Organelles & Proteins
Required For Mitosis Are
Produced
Cell Is Now Ready To Enter
M Phase (Mitosis)
Mitosis
Key Concept:
Biologists Divide The Events Of
Mitosis Into Four Phases:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Prophase
1st & Longest
Phase



Chromosomes
Become Visible
Centrioles
Separate &
Take Up
Position On
Opposite Sides
Of The Nucleus
Spindle Begins
To Form
Prophase
In Animals
Spindle Fibers
Attach To
Centromere On
Each Chromatid
In Plants
No Centromere,
Spindle Fibers
Still Form From
Centrosomes
Late Prophase


Nucleolus
Disappears
Nuclear
Envelope
Breaks Down
Metaphase
Short
Just A Few Minutes
 Chromosomes Line
Up Across Center Of
The Cell
 Microtubules
Connect The
Centromere To The
Poles Of The
Spindle
Anaphase



Centromeres
Separate
Sister
Chromatids
Separate
Each Set Of
Chromosomes
Pulled To Their
Poles
Telophase




Chromosomes
Disperse
New Nuclear
Envelopes Form
Spindle Breaks
Apart
Nucleolus
Reforms
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
Cytokinesis In Plants
A New Cell Plate
Forms In The
Middle Of The Cell
Which Attaches To,
And Becomes Part
Of, The Cell Wall
Chapter 10
Cell Growth & Division
Section 10-3
Regulating Cell Growth
Objectives


How is the cell cycle regulated?
How are cancer cells different from other
cells?
Controls On Cell Division
When Cells In Cell Cultures Come In
Contact With Each Other, They Stop
Growing.
Why?
Controls On Cell Division
If A Hole Is Made In The Cell Culture, Cell
Growth Will Restart & Continue Until The
Hole Is Filled.
Why?
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?
Cell Cycle Regulators
Key Concept:
Cyclins Regulate The Timing Of The
Cell Cycle In Eukaryote Cells.
 Discovered In The 1980’s
 Cyclins Are A Family Of Closely
Related Proteins That Rise & Fall
Within The Cell With The Cell Cycle
Cyclins & Cell Cycle
Cell Cycle Regulators
Cyclins
When Injected
Into NonDividing
Cells, Cyclins
Cause Mitotic
Spindles To
Form.
Cell Cycle Regulators
Cyclins
When Injected
Into NonDividing
Cells, Cyclins
Cause Mitotic
Spindles To
Form.
Cell Cycle Regulators
Cyclins
When Injected Into NonDividing Cells, Cyclins Cause
Mitotic Spindles To Form.
Cell Cycle Regulators
Other Regulator Proteins
Continue To Be Found.
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
Cyclins & Cell Cycle
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
Growth Factors
 Very
Active During
 Embryonic
Development
 Wound Healing
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
Uncontrolled Cell Growth
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.
Uncontrolled Cell Growth
Metastasis
Cancer Cells
Break Loose
From The
Tumor And
Invade
Tissues
Throughout
The Body
Some Carcinogen Sources
Smoking
Radiation
Viral Infection
p53 Gene


Usually Stops The Cell Cycle Until
Chromosomes Have Been Properly
Replicated.
High Percentage Of Cancers Cells
Have Defects At This Gene Site