chapter 8. cells must divide for growth repair cells cannot just continue to grow larger for two...
TRANSCRIPT
Chapter 8
Cells must divide forGrowthRepair
Cells cannot just continue to grow larger for two reasons:Exchanging materials
The surface area of the cell membrane must be large enough to support the volume of the cell.
Otherwise, the cell struggles keeping up with the exchange rate of food, oxygen and water across the membrane.
Information overloadToo many demands on the DNA to get its
information where it is needed.
Mitosis-The process by which a cell divides, forming
two “daughter” cellsThese daughter cells are identical to the
parent cell
Which cells ?Eukaryotic somatic (body) cells undergo
mitosisProkaryotic cells go through a process called
binary fission
ChromosomesMade up of DNA wrapped tightly around
histone proteinsDNA + histones = chromatin fiber and looks
like “beads on a string”During mitosis chromatin condenses and
coils to form chromosomes
Chromosome:Sister chromatids- Each side of a duplicated
chromosomeCentromere- Center of a chromosome, holds
sister chromatids together
Chromosome number varies for each speciesHumans= 46 Cat= 38Fruit fly= 8
The cell cycleMitosis is part of the cell’s life cycleThis cycle includes the following stages:
InterphaseMitosisCytokinesis
Interphase The longest phase of the cell cycleThe cell prepares to divide3 phases, or checkpoints, in Interphase
Phases of InterphaseG1 - intense cell growth, cells contents
duplicatedS - DNA is replicated (copied)G2 - more growth and final preparation for cell
divisionG0- cell enters this phase when something is
wrong and it either can’t or won’t divide. Ex: unstable environment, DNA was copied incorrectly, more cells not needed at that time
The Cell Cycle
After a cell goes through all the checkpoints, it is ready to divide!
The Mitotic phase of the cell cycle includes
ProphaseMetaphaseAnaphaseTelophase
ProphaseNuclear envelope disappearsChromatin condensesChromosomes are first visibleCentrioles split and move to opposite sides of
the cell
Prophase
Prophase
MetaphaseChromosomes line up in the middle of the
cell (equator)
Spindle fibers connect to chromosomes at the centromere
Metaphase = Middle
Metaphase
Metaphase (plant cell)
AnaphaseSister chromatids pulled apart to opposite
sides Spindle fibers shortenAnaphase = Away, or Apart
Anaphase
Anaphase
TelophaseTwo sets of genetic information on either side
of the cellNuclear envelope reforms around each setChromosomes no longer visible (unravel into
chromatin again)
Telophase
After mitosis is complete, the cell has one thing left to do- split! (cytokinesis)
CytokinesisSplitting of the cytoplasmForms two new distinct “daughter” cells Two cells are genetically identicalIn animals- Cell membrane “pinches off”In plants- Cell plate forms
CytokinesisIn animals: Cell membrane “pinches off”
In plants: Cell plate forms
Video linkshttp://www.youtube.com/watch?v=VlN7K1-
9QB0
http://www.youtube.com/watch?v=nPG6480RQo0&feature=related
THE END