Cell Growth and Division Chapter 10

Why are cells so small? DNA DNA –Messages from the nucleus must be able to reach all parts of the cell Diffusion Diffusion –Nutrients must enter and wastes must leave –If the cell was too big, diffusion would happen too slowly

Why are cells so small? Surface Area vs. Volume Surface Area vs. Volume –As a cell grows larger, the volume increases faster than the SA –A bigger cell needs more nutrients, but has relatively less SA to take in those nutrients

Surface Area vs. Volume Cell Size 5 cm 10 cm Surface Area (l×w×6) 150 cm cm 2 Volume (l×w×h) 125 cm cm 3 SA to Volume Ratio 150/125 = 6:5 600/1000 = 6:10

Cell Cycle Cells divide before growing too large Cells divide before growing too large Before dividing, cells must prepare Before dividing, cells must prepare Preparation = Interphase Preparation = Interphase –G 1 phase: Cell grows larger –S phase: Cell makes new DNA for daughter cell –G 2 phase: Cell makes new organelles for daughter cell

Cell Cycle

Chromosomes Each chromosome is replicated during the S phase Each chromosome is replicated during the S phase A replicated chromosome has two identical sister chromatids connected by a centromere A replicated chromosome has two identical sister chromatids connected by a centromereCentromere Sister Chromatids

Mitosis

Mitosis Four Stages: Four Stages: –Prophase (pro- means first) –Metaphase (meta- means middle/after) –Anaphase (ana- means apart) –Telophase (telo- means far away/end)

Prophase Chromatin condenses into chromosomes Chromatin condenses into chromosomes Nuclear envelope and nucleolus disintegrate Nuclear envelope and nucleolus disintegrate Centrioles migrate to opposite ends of the cell Centrioles migrate to opposite ends of the cell Spindle fibers form in foot ball shape across cell Spindle fibers form in foot ball shape across cell Chromosomes condensing

Prophase

Metaphase Chromosomes line up in the middle (equator) of the cell Chromosomes line up in the middle (equator) of the cell Spindle fibers attach to centromeres Spindle fibers attach to centromeres

Metaphase

Anaphase Sister chromatids separate Sister chromatids separate Spindle fibers shorten, pulling chromatids to opposite ends of cell Spindle fibers shorten, pulling chromatids to opposite ends of cell Animal cells begin to pinch in Animal cells begin to pinch in Plant cells begin to form cell plate in the middle Plant cells begin to form cell plate in the middle

Anaphase

Telophase Nuclear membrane built from ER around each set of chromosomes Nuclear membrane built from ER around each set of chromosomes Nucleolus reforms in each nucleus Nucleolus reforms in each nucleus Chromosomes become mass of chromatin Chromosomes become mass of chromatin

Telophase Two cells dividing into four

Cytokinesis Final division of cytoplasm resulting in two daughter cells Final division of cytoplasm resulting in two daughter cells Animals – CM pinches together Animals – CM pinches together Plants – Cell plate forms new CM dividing the daughter cells Plants – Cell plate forms new CM dividing the daughter cells

Plant Cell Division

Which phases can you see? Prophase Metaphase Anaphase Telophase Interphase

Knowing when to divide Cyclins Cyclins –Protein that regulates the cell cycle in eukaryotes Internal regulators – tell the cell when to enter mitosis Internal regulators – tell the cell when to enter mitosis External regulators – control the rate of the cell cycle External regulators – control the rate of the cell cycle

Cellular Response to Injury

Effect of Cyclins Cytoplasm is removed from cell in mitosis Cytoplasm is injected into a second cell in G 2 phase Second cell enters mitosis

Cancer Cancer results when cells do not respond to cell cycle regulators Cancer results when cells do not respond to cell cycle regulators Cells grow unregulated, forming a tumor Cells grow unregulated, forming a tumor Tumor damages surrounding tissue Tumor damages surrounding tissue

Leukemia – Blood cancer

Mammary (Breast) Cancer

Skin Cancer