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Cell Cycle Notes

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Cell Cycle Notes Objectives • MC.2.B.1 – Construct a hierarchy of life from cells to ecosystems • MC.2.B.8 – Describe the main events in the cell cycle • MC.2.B.9 – List in order and describe the stages of mitosis Cell Cycle Notes • Are you a single celled organism or a multi-cellular organism? • Do we have any human-sized single- celled organisms? • Why or why not? 3 Factors that limit cell size: 1. Diffusion rate—a large cell would die before getting necessary nutrients; diffusion is inefficient in a large cell. 2. DNA—insufficient amount to support protein production. 3. Surface area-to-volume ratio—surface area cannot increase fast enough to support the volume of the cell. Chart for Recording Surface Area-to-Volume Ratio SA:V 1x1 cell Surface area-to-volume ratio Surface area is found by length x width x 1 cm number of sides. 1 cm SA = 1 x 1 x 6 = 6cm2 SA:V Volume is found by length x width x height. 6:1 1x1 cell V = 1 x 1 x 1 = 1cm3 Surface area-to-volume ratio Surface area is found by length x width x 2 cm number of sides. 2 cm SA = 2 x 2 x 6 = 24cm2 SA:V Volume is found by length x width x height. 1x1 cell 6:1 3 V = 2 x 2 x 2 = 8cm 2x2 cell 24:8 Surface area-to-volume ratio Surface area is found by length x width x 4 cm number of sides. 4 cm 2 SA = 4 x 4 x 6 = 96cm SA:V Volume is found by length 1x1 cell 6:1 x width x height. 2x2 cell 24:8 V = 4 x 4 x 4 = 64cm3 4x4 cell 96:64 Surface area-to-volume ratio Surface area is found by length x width x 8 cm number of sides. 8 cm 2 SA = 8 x 8 x 6 =384cm SA:V Volume is found by length 1x1 cell 6:1 x width x height. 2x2 cell 24:8 V = 8 x 8 x 8 = 512cm3 4x4 cell 96:64 8x8 cell 384:512 • Cell division is the process by which new cells are produced from one cell. • Chromosomes—DNA, carriers of the genetic material that is copied and passed from generation to generation of cells. • Chromatin—long strands of DNA wrapped around proteins. • Cell cycle—the sequence of growth and division of a cell. • Interphase •Mitosis •cytokinesis Interphase • Cell grows in size and carries on metabolism. • 3 phases of interphase: 1. G1—rapid growth and metabolic activity. 2. S—DNA synthesis and replication. 3. G2—centrioles replicate; cell prepares for division. Mitosis • Process by which one cell divides to create two daughter cells, each containing a complete set of chromosomes. • 4 phases (PMAT) – Prophase – Metaphase – Anaphase – Telophase Prophase 1st & longest phase; • Chromatin coils into visible chromosomes • Sister chromatids—2 halves of the duplicated chromosomes. • centromeres—hold sister chromatids together in center. Prophase • Nucleus disappears. • Centrioles migrate to opposite ends of the cell • Small, dark structures made of microtubules located outside nucleus; play a role in chromatid separation. • Spindle forms •Football shaped cagelike structure consisting of microtubules; plays a role in chromatid separation. Metaphase 2nd & shortest phase; • Doubled chromosomes become attached to the spindle fibers by their centromeres. •Chromosomes are pulled by spindle and line up on the midline of the cell. •One sister chromatid’s spindle fiber extends to one end and the other extends to the other end. Anaphase Marked by the separation of sister chromatids • centromeres split apart and chromatid pairs separate •Spindle fibers shorten pulling the chromatids apart. Telophase Begins as chromosomes reach opposite ends of the cells • The opposite of prophase! • Chromosomes unwind to begin directing cell functions • Spindle breaks down • Nucleolus reappears and nuclear envelope forms around each set of chromosomes. Cytokinesis Division of the cytoplasm • Animal cells— • Plant cells—have a plasma membrane rigid cell wall. pinches in along the equator and cell •Cell plate is laid membrane forms down on the equator around it. and cell membrane forms around it. Results of mitosis Cell division 2 daughter cells tissue organs organ systems Control of Cell Cycle Enzymes control Genes control enzymes cell cycle When a breakdown occurs, we have cancer uncontrolled cell division .
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