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 which waste products leave cell depends on _______________________ of cell=total area of cell membrane DNA Surface area

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 divisionreplicates

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 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 G 2 phase S phase G 1 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 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