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Multicellular Life Multicellular Life Cell Cycle Cell Division I. Unicellular Life A. A single cell makes up the entire organism 1. All prokaryotes (Archaebacteria & Eubacteria) 2. Some Eukaryotes (Protsits & Yeasts) II. Multicellular Life A. Organisms composed of two or more cells (up to trillions of cells) II. Multicellular Life B. Levels of Organization 1. 2. 3. 4. 5. Individual Cell Tissue Organ Organ System Organism II. Multicellular Life CELL-smallest unit of life TISSUE- group of specialized cells ORGAN- group of tissues with specific function ORGAN SYSTEM- multiple organs doing the same function ORGANISM- many organ systems make up a single living thing II. Multicellular Life C. Cell Specialization 1. Cells become efficient in one process and are dependent on other cells for the necessities of life. a) Only found in Multicellular organisms b) Cells have a specific role or function that benefits the whole organism 2. All cells in the same organism will have the exact same DNA 3. Different cells use different sections of the DNA called genes. II. Multicellular Life C. Cell Specialization 4. Examples: a) Blood cells carry oxygen b) Muscle cells contract c) Nerve cells used for response and signals II. Multicellular Life D. Limits to Cell Growth 1. Cells must divide when they become too large. 2. Large cell problems: a) DNA Overload Do cells get larger and larger? • DNA unable to meet the needs of a growing cell • Growth without limitsor would cause information Docrisis cells divide to create more cells? b) Exchanging materials • Unable to efficiently move materials in (C6H12O6, O2, etc.) and wastes out (CO2, H2O, etc.) via the cell membrane c) Use food and oxygen more quickly II. Multicellular Life D. Limits to Cell Growth 3. Ratio of Surface area to Volume a) Volume increases more rapidly than Surface area as the cell grows. b) If ratio becomes to small the cell has difficulties exchanging materials. c) Cell volume determines the amount of waste production. II. Multicellular Life D. Limits to Cell Growth 4. Cell division a) When cells become too large they must divide forming two “daughter” cells b) DNA must replicate first in order for each daughter cell to have a complete copy of DNA c) This ensures that cells have a large (high) surface area to volume ratio (SA:V) II. Multicellular Life D. Limits to Cell Growth 3. Ratio of Surface area to Volume Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume III. Cell Cycle Cell Cycle includes Interphase Grows & replicates DNA M phase (Mitosis) is divided into G1 phase S phase DNA replication Cell Division is divided into G2 phase Prophase Prepare for Prepare mitosis (organelles & molecules made) Metaphase Anaphase Telophase Middle Away Two cells III. Cell Cycle A. There are two main phases of the cell cycle 1. Interphase 2. M- Phase III. Cell Cycle B. Interphase 1. Longest phase of the cell cycle. Cells the majority of their lives in this phase. a) G1-What 1st Growth is the point of the cell • replicating Cell increases in size and carries out normal DNA in the S phase? life activities b) S- DNA Replication • DNA is copied c) G2- 2nd Growth • Prepares to divide and copies organelles III. Cell Cycle C. M-Phase: Cell Division 1. Mitosis- Division of the nucleus after Interphase. a) b) c) d) Prophase Metaphase Anaphase Telophase 2. Cytokinesis- Division of the cytoplasm III. Cell Cycle C. M-Phase: Cell Division 1. Mitosisa) Prophase- PREPARE • Chromatin condenses into chromosomes • Centrioles separate & spindle begins to form • Nuclear envelope breaks down III. Cell Cycle C. M-Phase: Cell Division 1. Mitosisb) Metaphase- MIDDLE • Chromosomes line up in the middle • Chromosomes connect to spindle fibers at centromere III. Cell Cycle C. M-Phase: Cell Division 1. Mitosisc) Anaphase- AWAY • Spindle fibers pull sister chromatids apart • Sister chromatids are pulled to opposite sides of the cell III. Cell Cycle C. M-Phase: Cell Division 1. Mitosisd) Telophase- TWO • Chromosomes gather at opposite ends • Two new nuclear envelopes form III. Cell Cycle C. M-Phase: Cell Division 2. Cytokinesis Cleavage a) Cytoplasm pinches in halfFurrow b) Each newly formed daughter cell has equal numbers of chromosomes c) In plant cells: a cell plate forms to separate the 2 cells. III. Cell Cycle Let's watch the whole process now. Source: http://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf III. Cell Cycle D. G0 Phase 1. Resting phase a) No division b) Some cells never leave this phase • Nerve cells c) Some cells never enter this phase • Skin cells IV. Regulating the Cell Cycle A. Controls 1. When cells come in contact with each other, they respond by not growing and dividing. a) If cells are removed or separated from each other, cells begin dividing to fill empty space • Cuts, Scrapes Injury Normal growth Stop growth Cell growth & division for repair IV. Regulating the Cell Cycle A. Controls 2. Cyclins a) Proteins that regulate the timing of the cell cycle in eukaryotes & jumpstart cell division b) Internal Regulators- Proteins that respond to events inside the cell. (the cell won’t divide until DNA replicates) c) External Regulators- Proteins that respond to events outside the cell. (growth factor molecules on neighboring cells and hormones) How to make a cell start cell division? A sample of cytoplasm is removed from a cell in mitosis. The sample is injected into a second cell in G2 of interphase. As a result, the second cell enters mitosis. IV. Regulating the Cell Cycle B. Uncontrolled Cell Growth: Cancer 1. Cells lose ability to control growth 2. Cells stop responding to signals that control growth a) Cancer cells may have a defect in the P53 gene (internal regulator). This gene normally stops the cell cycle until all chromosomes have been replicated properly. If it is defective or damaged, cells will accumulate chromosome damage and stop responding to cell cycle regulators. IV. Regulating the Cell Cycle B. Uncontrolled Cell Growth: Cancer IV. Regulating the Cell Cycle B. Uncontrolled Cell Growth: Cancer 3. Treatment a. Radiation – gamma rays b. Chemotherapy- Chemicals c. Removal of Tumor- Surgery Kills good and bad Cells