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Cell Growth and Division
Chapter 10
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Why would we need new cells???
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Growth Repair Cell death
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Does cell size Matter? Comparison of cells to everyday items we see with our eyes with ones that need a microscope. Write down two observations or reactions to the cell size comparisons.
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Which type of cell is more efficient?
Why?
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Limits of cell growth Why cells stay small…and divide DNA Overload
Larger cells mean more demand of DNA Exchange of material Surface area affects exchange rate Surface area Volume increase more than surface area
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Before the cell becomes too large, it divides into two “daughter” cells in a process called Cell Division
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Cell division
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How is prokaryotic and eukaryotic cell division different?
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Cell Division Prokaryotes Binary Fission Eukaryotes Mitosis Meiosis
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Cell Cycle Series of events that that cells go through as they grow and divide
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3 parts of the cell cycle:
Interphase Mitosis Cytokinesis
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INTERPHASE- 3 phase G1 phase Monitor environment and cell size
Checks for DNA damage grows Organelles prep for cell division Cell spends most of its life in Interphase
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S phase DNA is copied
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G2 phase Intracellular components replicated
Last chance for growth prior to division
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Mitosis Division of the nuclear material 4 phases
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Cytokinesis Division of the cytoplasm
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Internet activity Cell Plate activity
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Mitosis animation
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Chromosomes Compact, coiled DNA Sister Chromatids Centromere
One half of the chromosome Centromere Between the two chromatids holds them together
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Mitosis How all cells divide EXCEPT reproductive cells
The cytoplasm and nucleus both divide Results in two cells that are genetically identical
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Prophase DNA is shortened and tightened into chromosomes
Nucleolus & nuclear membrane break down & disappear Two centrosomes appear Spindle fibers appear
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Metaphase Spindle fibers move chromosomes to the center of cell
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Anaphase Chromatids separate at the centromere and are pulled to opposite poles of cell by spindle fibers
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Telophase Spindle fibers break down Chromosome loosens up
Nuclear envelope forms around each set of chromosomes Nucleolus forms
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Cytokinesis
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Cytokinesis-in animals
Cell membrane pinches inward creating a cleavage furrow Eventually leads to two cells
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Cell Plate Only in plants Cell plate forms between two nuclei
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Mitosis/cell cycle Video
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Regulation of the cell cycle
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Not all cells divide at the same time
Cell type Life span Esophagus 2-3 days can divide Small intestine 1-2 days can divide Large intestine 6 days can divide Red blood cells <120 days cannot divide White blood cells 0 hrs – decades many do not divide Smooth muscle Long lived can divide Heart muscle Long lived cannot divide Nerve cells Long lived most do not divide Stomach cells 5 days Nerve cells in brain As old as you are Liver 1-1.5 years Adult skeleton 7-10 years Outer layer of skin 2 weeks
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Changes in mitosis Aging Cancer mutations
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AGING Mitosis begins after fertilization and continues until death.
The rate of mitosis slows down with age.
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Control of the Cell Cycle
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Cyclins -Proteins that regulate the a cell’s progression through the cell cycle
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CDKs (cyclin dependent kinases)- proteins that stop cells from progressing through the cell cycle
P53 – stops at G1 to; activates DNA repair if needed; triggers cell death if damage If this is absent can cause cancer P27- blocks entry into the S phase Breast cancer diagnosis is determined by p27 levels
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An abnormal cell should not be able to pass checkpoint
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When Control is Lost: Cancer
Cancer results if cells do not respond to control mechanisms and start growing uncontrollably
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CANCER – Cells mutate and grow, passing checkpoints
Normally a mutant cell is destroyed or self destructs. Apoptosis This does not occur in cancer cell
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Cancer cell division Unlike normal cells, cancer cells continue to divide indefinitely, even if they become densely packed. Cancer cells will also continue dividing even if they are no longer attached to other cells.
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Metastasis A cancer tumor grows and spreads to other parts of body
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Cancer animation
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Causes of Cancer carcinogen - Any substance that can induce or promote cancer. 2) Mutagens – A substances that cause mutations.
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KINDS OF CANCER Carcinomas- tumors grow in the skin and lining of organs. Ex. Lung and breast cancer Sarcomas- tumors that grow in bone and muscle tissue. Lymphomas- tumors that grow in the lymph and blood. Ex. Leukemia.
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Cell Differentiation
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Stem Cells- another way to produce new cells
Cellular Reproduction Stem Cells- another way to produce new cells Unspecialized cells that can develop into specialized cells when under the right conditions
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Embryonic Stem Cells – unspecialized cells
Cellular Reproduction Embryonic Stem Cells – unspecialized cells After fertilization, the resulting mass of cells divides repeatedly until there are about –150 cells. These cells have not become specialized.
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Cell differentiation the process by which a less specialized cell becomes a more specialized cell type.
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Cellular Reproduction
Adult Stem Cells Found in various tissues in the body and might be used to maintain and repair the same kind of tissue
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stem cells
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