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Biology

This biology chapter explores the limits to cell growth, the role of chromosomes in cell division, and the control mechanisms of the cell cycle. Topics covered include DNA overload, exchanging materials, surface area to volume ratio, mitosis, cytokinesis, and cell cycle regulators.

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Biology

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  1. Biology Ch. 10 Cell Growth and Division Core Content: SC-HS-3.4.3

  2. 10–1 Cell Growth A. Limits to Cell Growth 1. DNA “Overload” 2. Exchanging Materials 3. Ratio of Surface Area to Volume 4. Cell Division

  3. Limits to Cell Growth • The larger a cell becomes, the more demands the cell places on its DNA. • The cell has “DNA overload”, and the needs of the growing cell can no longer be met. • The more trouble a cell has moving enough nutrients and wastes across the cell membrane.

  4. Surface area to Volume Ratio • As a cell grows, the volume of the cell increases faster than the surface area. • The resulting decrease in the cell’s ratio of surface area to volume makes it difficult for the cell to move needed materials in and waste products out.

  5. Ratio of Surface Area to Volume in Cells Cell Size Cell Size Surface Area (length x width x 6) Surface Area (l x w x 6) Volume (l x w x h) Surface area to Volume ratio

  6. 10–2 Cell Division A. Chromosomes B. The Cell Cycle C. Events of the Cell Cycle D. Mitosis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase E. Cytokinesis

  7. Cell Division • Before it becomes too large, a growing cell must divide into two “daughter” cells. This is cell division. • Before cell division occurs, the cell copies its DNA. This ensures that each daughter cell gets a complete set of genetic information. • Division increases the cell’s surface area to volume ratio.

  8. Chromosomes • Chromosomes are made of DNA, which carries the cell’s coded genetic information, and proteins. • Cells of each organisms have a specific number of chromosomes. Ex) humans have 46 • Chromosomes are not visible except during cell division. • Each chromosome consists of two identical “sister” chromatids that are attached at the centromere.

  9. The Cell Cycle • During the cell cycle, a cell grows, prepares for division, and divides to form two new daughter cells. • Interphase is the period between divisions, and includes G1, S, and G2 phases. • The M phase follows interphase, and includes mitosis and cytokinesis.

  10. M phase (Mitosis) Interphase G1 phase S phase G2 phase Prophase Metaphase Anaphase Telophase Concept Map Section 10-2 Cell Cycle includes is divided into is divided into

  11. Interphase • Interphase takes much longer than actual cell division. • G1: Cells do most of their growing. Cells increase in size and synthesize new proteins and organelles. • S: DNA is copied • G2: Cell prepares for mitosis, makes organelles and structures needed for cell division

  12. Figure 10–4 The Cell Cycle Section 10-2 G1 phase M phase S phase G2 phase Go to Section:

  13. Mitosis • Following the events of Interphase, the cell will begin to divide. This is mitosis. • Biologists divide mitosis into four phases: prophase, metaphase, anaphase, and telophase

  14. Prophase • The first and longest phase of mitosis is prophase. • During prophase, the chromatin condenses to form chromosomes. • The centrioles separate, and a spindle begins to form. • The nuclear membrane breaks down.

  15. Metaphase • The stage following prophase is metaphase. • During metaphase, the chromosomes line up across the center of the cell. • Each chromosome is connected to a spindle fiber at its centromere.

  16. Anaphase • Following metaphase is anaphase. • During anaphase, the sister chromatids separate into individual chromosomes and are moved apart. • The chromosomes form groups near the poles of the spindle. • Anaphase ends when the chromosomes stop moving.

  17. Telophase • The fourth and final stage of mitosis is telophase. • The chromosomes gather at opposite ends of the cell, and lose their distinct shapes. • Two nuclear membranes begin to form.

  18. Cytokinesis • Cell division is not complete until cytokinesis occurs. Cytokinesis is division of the cytoplasm. • In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two equal parts. • In plants, a cell plate forms midway between the divided nuclei. The cell plate gradually develops into a separating membrane.

  19. Cleavage furrow in animal cells

  20. Cell plate forming in plant cell

  21. 9–3 Regulating the Cell Cycle A. Controls on Cell Division B. Cell Cycle Regulators 1. Internal Regulators 2. External Regulators C. Uncontrolled Cell Growth

  22. Cell Cycle Regulators • Cyclins regulate the timing of the cell cycle in eukaryotic cells. • Proteins that respond to events inside the cell are called internal regulators. • Proteins that respond to events outside the cell are called external regulators. • Most cells grow until they come in contact with other cells, then they stop (contact inhibition).

  23. Control of Cell Division Go to Section:

  24. Section 10-3 Figure 10–8 Effect of Cyclins A sample is injected into a second cell in G2 of interphase. A sample of cytoplasm is removed from a cell in mitosis. As a result, the second cell enters mitosis.

  25. Uncontrolled cell growth • Cancer cells do not respond to the signals that regulate the growth of most cells. • A defect in a gene called p53 has been found in many types of cancer cells. • They continue to grow out of control, and can form masses of cells called tumors. • Tumors can damage surrounding tissues.

  26. Benign vs. Malignant tumors • If the abnormal cells remain at the original site, the tumor is BENIGN and can usually be surgically removed. • If the tumor invades other organs and impairs their function, the tumor is MALIGNANT. • The spreading of cancer cells is METASTASIS.

  27. BREAST CANCER

  28. BREAST CANCER CELL

  29. NORMAL MAMMOGRAM CANCEROUS MASS

  30. Apoptosis • Programmed cell death. • Usually shrink and shrivel in a controlled process. • Example: development of hands and feet. Your hands and feet have webbing between them in utero. But when a baby is born this webbing is gone because of apoptosis. • Example: leaves falling off trees and plants in autumn.

  31. Stem Cells • Unspecialized cells that can develop into specialized cells when under the right conditions. • Two types: Embryonic and adult stem cells. • Embryonic—after fertilization the resulting mass of cells divides rapidly until there are about 100-150 cells. These are cells that have not become specialized yet and can be used to repair damaged cells in others but is highly controversial.

  32. Adult stem cells—found in various tissues in the body and might be used to maintain and repair the SAME kind of tissue in which they are found.

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