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Cell Growth

Cell Growth. Chapter 10 Section 1. Why do cells divide instead of just growing larger????. The larger a cell becomes, the more demands the cell places on its DNA. Hard to move materials (nutrients/wastes) around cell Movement of materials dependent on cell’s volume! “DNA” overload

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Cell Growth

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  1. Cell Growth Chapter 10 Section 1

  2. Why do cells divide instead of just growing larger???? • The larger a cell becomes, the more demands the cell places on its DNA. • Hard to move materials (nutrients/wastes) around cell • Movement of materials dependent on cell’s volume! • “DNA” overload • The information that controls cell function is stored in the cell’s nucleus and is known as DNA • One copy of DNA in a cell • Information crisis

  3. Cell = Town Analogy • Small town with a few thousand books • If many more people move into town, all the books will get checked out • People will have to wait for books • Same with “genetic information” getting around a cell

  4. Cell Size Limitations • Variety of shapes and sizes • Red blood cells – 8 micrometers • Nerve cells – length of 1 meter • Diffusion limits cell size • What regulates diffusion in the cell? • Cell membrane • Over large distance, process becomes slow and inefficient – too hard to move substances over large distances • DNA limits cell size • if cell is too large, not enough DNA to support protein production (DNA blueprint for proteins)

  5. Surface area to volume ratio limits size

  6. Volume increase more rapidly than surface area. • Cell size doubles, 8x as much volume, but only 4x as much surface area

  7. Cell = Town Analogy • Town has two-lane main street • Population increases, street size remains the same • Encounter more________? • Same with a cell • Difficult to get oxygen and nutrients in • Difficult to get waste products out

  8. Division of Cell • Before a cell becomes too large, it divides • Forms two “daughter” cells • This is called cell division • DNA must replicate (copies) • Each new “daughter” cell receives a copy of DNA • Keeps increased surface area to volume ratio • Keeps cell functions efficient!

  9. Red Blood Cells Red Blood Cell Blood Circulatory System Nerve Cell Spinal Cord Nervous System

  10. Cell Division Chapter 10 Section 2

  11. Need copies of DNA for each cell, right??? • Must copy DNA • Then, prokaryotes (bacteria) just divide up contents of the cell • Eukaryotes – much more complex • Mitosis – first stage • Cytokinesis – second stage • So, is mitosis sexual or asexual reproduction??? • “daughter” cells are identical • Source of new cells for multi-cellular organisms

  12. Chromosomes

  13. Chromosomes made of DNA • Organisms have specific number of chromosomes • Us – 46 • Fruit fly – 78 • Carrots – 18 • Not visible until cell division • When replicated, two identical sister chromotids! • *these are what separate during cell division • Attached in center by a centromere

  14. Sister Chromatids w/centromere

  15. Cell Cycle • *****OVERVIEW***** • 4 PHASES • M – mitosis and cytokinesis • G1 – gap 1 – cell growth • S – DNA Replication • G2 – gap 2 – prep for mitosis G1 phase M phase S phase G2 phase

  16. CELL CYCLE • Interphase = G1, S, G2 • G1 – most growing during this phase • S – chromosomes replicated • G2 – shortest phased, organelles produced

  17. Stages of Mitosis (M phase) • Mitosis • Division of cell which produces TWO daughter cells with complete set of chromosomes • 4 stages • PROPHASE • METAPHASE • ANAPHASE • TELOPHASE

  18.  Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  19.  Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

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

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

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

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

  24. Prophase • Chromatin coils up into visible chromosome • Called “sister chromatids” • Exact copies of DNA • Held together by centromere • Nucleus begins to disappear • Centrioles appear at ends of cell (chromatids move toward these) • Spindles form (chromatids move along these)

  25. Prophase • Onion cell

  26. Metaphase (middle) • Chromosomes attach to spindle fibers by centromere • Chromosomes line up in MIDDLE of cell

  27. Anaphase (apart) • Centromeres split • Sister chromatids separate from each other • Pulled apart by shortening of spindle fibers • Frog cell

  28. Anaphase • Onion Cell

  29. Telophase • Final phase of mitosis • Chromosomes unwind • Spindle breaks down • Nuclear envelope reappears • New double membrane forms between cells

  30. Cytokinesis • Division of cytoplasm • Plants • Cell plate forms • Animals • Cell membrane pinches in middle

  31. Results of Mitosis • Two identical cells • Continue cell processes • Cells - tissue-organ-organ system • Organ systems work for survival of organism

  32. Regulating the Cell Cycle Chapter 10 Section 3

  33. Normal Control of the Cell Cycle • Cell cycle controlled by proteins and enzymes • When cell’s lose control of the cell cycle, division goes unchecked • Cancer is a malignant growth resulting from uncontrolled cell division • Enzymes are controlled by genes • Gene – segment of DNA

  34. Cancer – a Mistake in the Cell Cycle • Unchecked division forms masses of tissue called tumors • These tumors deprive normal cells of nutrients • Cancer cells break off into circulatory system and spread to other parts of the body • This is called metastasis • 2nd leading cause of death in the USA

  35. Causes of Cancer • Genetic and Environmental factors • People in different countries develop different cancers • Japan, more stomach cancer than US • USA, more breast cancer than Japan • Environmental Factors • Cigarette smoke • Air and water • Exposure to UV radiation • Viral infections

  36. Cancer Prevention • Healthy lifestyle • Diets low in fat and high in fiber • Vitamin and minerals in your diet • Daily exercise

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