CELL GROWTH & DIVISION

2 Reasons why cells divide 1. DNA OVERLOAD As cell grows bigger demand on DNA genetic library becomes too great Ex: Small town library has 1000 books. As town grows and more people borrow books, there may be a waiting list to read the most popular titles http://www.adc.state.az.us/images/off-library.jpg

2 Reasons why cells divide 2. Material exchange can t keep up As cell grows bigger demand for transport across membrane is too great http://www.animationlibrary.com

Ability to transport of oxygen, food, waste across cell membrane depends on SURFACE AREA Need for these depends on CELL VOLUME As cell grows these DON T increase at the same rate

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 Go to Section:

BIGGER CELLS NEED MORE FOOD and OXYGEN, but CAN T TRANSPORT IT FAST ENOUGH or IN BIG ENOUGH QUANTITIES! http://www.animationlibrary.com

Multicellular organisms grow mainly by increasing cell number

DNA CAN BE: SPREAD OUT IN NON-DIVIDING CELLS CHROMATIN SCRUNCHED UP IN DIVIDING CELLS CHROMOSOMES

Chromosomes Chromosome animation

DNA in PROKARYOTES BACTERIAL DNA is CIRCULAR HAVE ONE CHROMOSOME NO NUCLEUS; DNA is found in the nucleoid region

DNA in EUKARYOTES (Plants & Animals) DNA is ROD-SHAPED CHROMOSOMES MANY PAIRS FOUND IN NUCLEUS http://cellbio.utmb.edu/cellbio/chrom2.jpg

Chromosome structure CHROMATIDS 2 identical arms CENTROMERE constricted area holds chromatids together HOMOLOGOUS PAIR 2 of each chromosome (one from mom; one from dad)

HOMOLOGOUS CHROMOSOMES SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT NOT! IDENTICAL (Don t have to have the SAME CHOICES) http://arnica.csustan.edu/biol3020/cell_division/cell_division.htm http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

CELL DIVISION in PROKARYOTES Bacteria reproduce using BINARY FISSION

CELL CYCLE = series of events that cells go through as they grow and develop cells alive cell cycle

CELL CYCLE INTERPHASE non-dividing phase G 1 - Grow bigger DNA is spread out as chromatin S - Synthesis (copy DNA) & chromosomal proteins G 2 - Grow bigger, make organelles & molecules needed for cell division

CELL DIVISION MITOSIS Nuclear division Prophase Metaphase Anaphase Telophase Cytokinesis Cytoplasm divides G 0 cell stops dividing (Ex: nerve cell)

Figure 10 4 The Cell Cycle Section 10-2 G 1 phase M phase S phase G 2 phase Go to Section:

INTERPHASE (G 1 - S - G 2 ) In between divisions Cells are in this phase most of the time Can see nucleus and nucleoli DNA spread out as chromatin Microtubules outside nucleus, centrioles Have doubled, organelles replicated Can t see chromosomes DNA gets copied (S) Cell gets ready to divide

Pearson Education Inc publishing as Pearson Prentice Hall PROPHASE 1st dividing phase DNA scrunches into replicated chromosomes Centrioles appear in centrosome region & move to poles Nuclear membrane & nucleolus disappear Spindle fibers form & attach to replicated chromosomes http://www.life.uiuc.edu/plantbio/102/lectures/08mit&veg102.html

Prometaphase Microtubules emerge from the centrioles at the poles=spindle fibers Microtubules attach to kinetochores throwing replicated chromosomes into agitated motion Asters form around centrioles

CENTROSOME region organizes spindle Spindle MICROTUBULES are part of cytoskeleton http://www.coleharbourhigh.ednet.ns.ca/library/organelle_worksheet.htm

METAPHASE Replicated chromosomes line up in middle and attach to spindle fibers Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www.science.siu.edu/plant-biology/plb117/jpegs%20cd/0247.jpg

ANAPHASE Centromeres split Centrioles pull chromatids apart Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www.science.siu.edu/plant-biology/plb117/jpegs%20cd/0247.jpg

Anaphase Kinetochores (found within chromosomes) are powered by ATP and walk the daughter chromosomes to opposite poles.

TELOPHASE See two nuclei (reverse prophase steps) Nuclear membrane & nucleolus return Chromosomes spread out as chromatin Centrioles disappear Spindle fibers disappear and go back to microtubles Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www2.bc.cc.ca.us/cnewton/biology%2011/mitosis.html

CYTOKINESIS Cytoplasm splits into 2 cells ANIMAL CELLS pinch cytoplasm in two with a (use of microfilaments) CLEAVAGE FURROW

CYTOKINESIS Cytoplasm splits into 2 cells PLANT CELLS can t pinch because they have a sturdy CELL WALL Plant cells separate cytoplasm by growing a CELL PLATE down the middle. http://www.eastcentral.edu/acad/depts/bi/plant_mitosis_nolabels.html

Figure 10 5 Mitosis and Cytokinesis Section 10-2 Centrioles Spindle forming Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Spindle Centriole Nuclear envelope reforming Cytokinesis Telophase Anaphase Individual chromosomes Centriole Metaphase Go to Section:

Concept Map Section 10-2 Cell Cycle includes Interphase M phase (Mitosis) is divided into is divided into G 1 phase S phase G 2 phase Prophase Metaphase Anaphase Telophase Go to Section: