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Chapter 10
Cell Growth And Division
I. Cell Growth
–
–
•
DNA
A. Limits to Cell Growth
2 reasons cells divide rather than continuing
to grow indefinitely:
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•
–
1) larger a cell grows,the more
demands on its _______
will not be making enough copies of DNA
as size increases---This would cause an
information crisis.
2)
difficult to move waste and
nutrients across cell
rate @ which waste products leave cell
depends on _______________________
of cell=total area of cell membrane
Surface area
– rate @ which food and Oxygen are used
up and waste produced depends on
_____________________
– RATIO OF SURFACE AREA TO VOLUMEassuming a cube shape,surface area=l x w
x 6…..volume= lx w x h….
ratio = SA /volume
Cell volume
Ratio of Surface Area to
Volume in Cells
Section 10-1
Cell Size
Surface Area
(length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area to
Volume
• Volume increases faster than surface
area/CAUSING RATIO TO
__________________..causing serious
problems for cell --Because a decrease
in the relative amount of cell membrane
available –compared to increase in cell
volume-decrease
B. Division of Cell-before a growing cell becomes
too large
Cell division solves the problem of increasing
size by reducing cell volume
-A cell divides into 2 daughter cells
=_______________________________
– This happens before a cell can get too
large
– DNA ___________________before cell
division,solving info crisis.
Cell division
replicates
C. Cell division and reproduction
• Asexual-takes one parent and produces
genetically identical offspringsimple,efficient and effective
• What problems could it present…?
• Some multicellular organisms
reproduce by budding---example-hydra
• Sexual-takes 2 parents-fusion of
reproductive cells-new genetic infosome from each parent-greater
diversity-advantage
• Comparing asexual and sexual• Asexua l,since it is quick is a survival
strategy
• Ok as long as conditions are favorable
• Sexual advantage is diversity
• Some do both-example-yeast
II. Cell Division Process
•
***simpler in prokaryotes
–
A. chromosomes –carries genetic info in
eukaryotes
– made up of ____________ and proteins
– cells of every organism have a specific #
of Chromosomes
– humans have___ Chromosomes
46
– fruit flies have 8
– usually not visible except in cell
division,when they condense
– ___________________before cell
division
Replicates or
copies
DNA
–each Chromosome consists of 2
identical __________________,which
separate from each other in cell
division
–chromatids attached
@__________________,usually near
middle
chromatids
centromere
II. Chromosomes & DNA
Replication
• A-DNA & Chromosomes
– In cytoplasm in prokaryotes
– In _______________________found in cell
nucleus in the form of a number of
chromosomes(46 humans,8 Drosophilia
and 22 Sequoia trees)
eukaryotes
•
1--DNA length
– 1.6 mm in E.coli(has 4,639,221 base pairs)--obviously it must be tightly folded
B. Cell Cycle
– ________________________is in- between
phase
– ______________________is the series of
events that a cell goes through during
growth and division….Where the cell
grows,prepare for division,divides into 2
daughter cells
interphase
Cell Cycle
–4 phases
• M= _______________________________
• S= ________________________________
• G1 and G2=
______________________________________
__________________
Mitosis and
cytokinesis
Chromsomes
replicate & DNA
synthesis,some
proteins synthesize
G1=cell growth/G2= organelles and molecules produced
Figure 10–4 The Cell Cycle
Section 10-2
G1 phase
M phase
S
phase
G2
phase
ANAPHASE
1) Prophase
–
–
–
–
–
–
centrioles
Longest phase
Chromosomes become visible
_______________________,2 tiny structures
near nuclear envelope-separate and take
positions on opposite ends of nucleus
Centrosome region helps organize
__________________-microtubules that help
separate chromosomes
Chromosomes attach to
__________________________
@ end chromosomes coil tightly and nuclear
envelope disappears
spindle
Spindle fibers
•
2) Metaphase•
•
•
chromosomes line up @ center
Centromeres go to 2 poles
3) Anaphase•
•
•
Centromeres split
Chromatids separate and become individual
_____________________
New chromosomes go to opposite poles and then
stop moving
chromosomes
• 4) Telophase• Chromosomes disperse into tangle of
material
• New nuclear envelopes
• Spindle breaks apart
• Nucleolus becomes visible
D. Cytokinesis-divison of cytoplasm
– Usually along w/ Telophase
– Cell plate forms in plants that becomes the
______________________________
– Occurs at cleavage furrow in
animals,where it pinches inward---too
rigid to pinch inward in plants
CELL WALL
III-Regulating Cell Cycle.
• Most cells in lab divide until coming in contact
w/other cells-similar in body
• _____________________= disorder in which some of
the body’s cells lose the ability to regulate growth
• They do not respond to signals that regulate growth
• Divide uncontrollably,making
___________________(masses of cells)/not all are
cancerous
• _____________=protein that regulates normal cell
cycle (in eukaryotes)
tumors
cancer
cyclins
• Cancer caused by defect in genes causing cell
growth and division-oncogene-caused by
carcinogens such as smoking,chew
tobacco,radiation,viruses,chemicalsCARCINOGENS,many cancers linked to abnormality
in p53 gene-normally halts cell cycle until all
chromosomes have been replicated
• Cancer treated by-surgery for tumor
removal,radiation-tarets DNA replication that is
happening at accelerated rate, chemotherapy---both
also affect normal cells
cyclins
• _________________=protein that regulates
normal cell cycle (in eukaryotes)-tells cells
it’s time to divide
• There are regulatory proteins internally and
externally to the cell-for example(internally)proteins that make sure replication has
happened before mitosis/externallyGROWTH FACTORS-Stimulate growth or
slow down growth-esp. important in embryo
or wound healing
• APOSTASIS-process of programming
cell death(which also can die by
accidents)-key role in tissue and organ
development-AIDS and Parkinson’s are
examples of if apoptosis is not
regulated