Chapter 10
Cell Growth And Division
I. Cell Growth– A. Limits to Cell Growth– 2 reasons cells divide rather than
continuing to grow indefinitely:• 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
DNA
Surface area
– rate @ which food and Oxygen are used up and waste produced depends on _____________________
– RATIO OF SURFACE AREA TO VOLUME-assuming a cube shape,surface area=l x w x 6…..volume= lx w x h…. ratio = SA /volume
Cell volume
Cell Size
Surface Area (length x width x 6)
Volume (length x width x height)
Ratio of Surface Area to Volume
Ratio of Surface Area to Volume in Cells
Section 10-1
• 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 offspring-simple,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 info-some 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– fruit flies have 8– usually not visible except in cell
division,when they condense– ___________________before cell division
DNA
46
Replicates or copies
–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
M phase
G2 phase
S phase
G1 phase
Figure 10–4 The Cell Cycle
Section 10-2
ANAPHASE
1) Prophase
– 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
centrioles
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)cancer tumors
cyclins
• Cancer caused by defect in genes causing cell growth and division-oncogene-caused by carcinogens such as smoking,chew tobacco,radiation,viruses,chemicals-CARCINOGENS,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/externally-GROWTH 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
