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