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Transcript
Materials move through cells by diffusion. Oxygen and food move into cells, while waste products move out of cells. How does the size of a cell affect how efficiently materials get to all parts of a cell? Work with a partner to complete this activity 1. On your bell work, make a drawing of a cell that has the following dimensions: 5 cm x 5 cm x 5 cm. Your partner should draw another cell about one half the size of your cell on their own bell work paper. 2. Compare your drawings. How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell? It would take twice the amount of time. 3.What is the advantage of cells being small? If cells are small, materials can be distributed to all parts of the cell quickly. Image from: http://www.bcps.org/offices/lis/models/life/images/grow.JPG CELL GROWTH & DIVISION 10-1 & 10-2 Image by Riedell Cell Reproduction • Cell Theory states that all cells come from pre-existing cells • Cells reproduce by cell division • Cells are constantly wearing out and are replaced by cell division 2 Reasons why cells divide DNA OVERLOAD 1. _____________________ 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 Material exchange can’t keep up 2. _____________________ 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 See relationship between volume and SA 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 Image from: http://www.bcps.org/offices/lis/models/life/images/grow.JPG Image by Riedell Multicellular organisms grow mainly by increasing cell number Reproduction: Not as simple as it looks. Reproduction presents a major problem for cells and organisms: (how can information be transmitted faithfully to progeny) = one bit of genetic information I II III IV The information transfer problem becomes more challenging as more bits of information are incorporated into the organism = one bit of genetic information One of life’s solutions to this challenge: “Package” the bits of information into single units called chromosomes = one bit of genetic information © 2003 John Wiley and Sons Publishers Fig 2.4 The structure of a highly condensed, replicated chromosome. DNA CAN BE: SPREAD OUT IN NON-DIVIDING CELLS CHROMATIN SCRUNCHED UP IN DIVIDING CELLS CHROMOSOMES Packaging of genetic material in prokaryotes and eukaryotes prokaryote cell eukaryote cell chromosomes DNA in PROKARYOTES • BACTERIAL DNA is CIRCULAR • HAVE ONE CHROMOSOME • NO NUCLEUS; ATTACHED TO CELL MEMBRANE http://www.origin-life.gr.jp/3202/3202121/fig6.jpg CELL DIVISION in PROKARYOTES Bacteria reproduce using BINARY FISSION __________________________________ http://fig.cox.miami.edu/~cmallery/150/mitosis/fission.jpg DNA in EUKARYOTES (Plants & Animals) • DNA is ROD-SHAPED CHROMOSOMES • MANY PAIRS • FOUND IN NUCLEUS http://cellbio.utmb.edu/cellbio/chrom2.jpg CELL CYCLE ______________ = a series of events that cells go through as they grow and develop; Cell Cycle takes 18-24 hours Organs which need to produce new cells continuously have the highest turnover. For example:Bone marrowproducing replacement blood cells The testes producing semen The cell cycle. © 2003 John Wiley and Sons Publishers Figure 10–4 The Cell Cycle Section 10-2 G1 phase M phase S phase G2 phase Go to Section: CELL CYCLE INTERPHASE – non-dividing phase G1- Grow bigger Cell is “doing its job” DNA is spread out as chromatin S - Synthesis (copy DNA) & chromosomal proteins G2- Grow bigger, make organelles & molecules needed for cell division CELL DIVISION M Stage = MITOSIS = Nuclear division • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis = Cytoplasm divides G0 – cell stops dividing (Ex: nerve cell) INTERPHASE (G1 - S - G2) In between divisions •Cells are in this phase most of the time •Can see nucleus or chromosomes •DNA spread out as chromatin… •DNA gets copied •Organelles get copied Pearson Education Inc publishing as Pearson Prentice Hall PROPHASE =1st dividing phase http://www.life.uiuc.edu/plantbio/102/lectures/08mit&veg102.html •DNA scrunches into chromosomes •Centrioles appear in centrosome region & move to poles •Nuclear membrane & nucleolus disappear •Spindle fibers form & attach to chromosomes The Spindle A spindle is a web type structure made up of microtubule fibres. It is essential for mitosis because it arranges the chromosomes into their correct positions in preparation for cell division. Mitotic centr A cell at metaphase Microtubul e a spindle CENTROSOME ________ region organizes spindle Spindle MICROTUBULES are part of cytoskeleton http://www.coleharbourhigh.ednet.ns.ca/library/organelle_worksheet.htm METAPHASE •Chromosomes line up in middle ___________ 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 apart •Centrioles pull chromatids_______ Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www.science.siu.edu/plant-biology/PLB117/JPEGs%20CD/0247.JPG TELOPHASE (reverse prophase steps) two •See ______ nuclei •Nuclear membrane & nucleolus return •Chromosomes spread out as chromatin •Centrioles disappear •Spindle fibers disappear Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www2.bc.cc.ca.us/cnewton/Biology%2011/Mitosis.html CYTOKINESIS = division of the cytoplasm to create 2 cells *ANIMAL CELLS pinch cytoplasm in two with a ______________________ CLEAVAGE FURROW *PLANT CELLS can’t pinch because CELL WALL they have a sturdy ____________ *Plant cells separate cytoplasm by CELL PLATE growing a _______________ down the middle. http://www.eastcentral.edu/acad/depts/BI/plant_mitosis_nolabels.html Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Go to Section: Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase REMEMBER! Interphase Prophase Metaphase Anaphase Telophase Go to Section: IPMAT Concept Map Section 10-2 Cell Cycle includes is divided into Go to Section: is divided into Concept Map Section 10-2 Cell Cycle includes Interphase M phase (Mitosis) is divided into is divided into G1 phase Go to Section: S phase G2 phase Prophase Metaphase Anaphase Telophase