Click on a lesson name to select. Cellular Reproduction Section 1: Cellular Growth Section 2: Mitosis and Cytokinesis Section 3: Cell Cycle Regulation

Cellular Growth Ratio of Surface Area to Volume Section 1 Cellular Reproduction

 As the cell grows, its volume increases much more rapidly than the surface area.  The cell might have difficulty supplying nutrients and expelling enough waste products. Section 1 Cellular Growth

Transport of Substances  Substances move by diffusion or by motor proteins.  Diffusion over large distances is slow and inefficient. Cellular Reproduction  Small cells maintain more efficient transport systems. Section 1 Cellular Growth

Cellular Communications  The need for signaling proteins to move throughout the cell also limits cell size.  Cell size affects the ability of the cell to communicate instructions for cellular functions. Cellular Reproduction Section 1 Cellular Growth

The Cell Cycle  Cell division prevents the cell from becoming too large.  It also is the way the cell reproduces so that you grow and heal certain injuries. Cellular Reproduction  Cells reproduce by a cycle of growing and dividing called the cell cycle. Section 2 Cellular Growth

 Interphase is the stage during which the cell grows, carries out cellular functions, and replicates.  G 1 - cell growth  S - chromosomes are duplicated  G 2 - cell growth Cellular Reproduction Section 2 Cellular Growth

 Mitosis(M phase) is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. Cellular Reproduction Section 2 Cellular Growth  Cytokinesis(C phase) is the method by which a cell’s cytoplasm divides, creating a new cell.

Section 2

Cellular Reproduction The Stages of Interphase  The first stage of interphase, G 1  The cell is growing, carrying out normal cell functions, and preparing to replicate DNA. Section 1 Cellular Growth

Cellular Reproduction The Second Stage of Interphase, S  S stands for synthesis of DNA  The cell copies its DNA in preparation for cell division. Section 1 Cellular Growth

Cellular Reproduction The Third Stage of Interphase, G 2  The cell continues to grow and prepares for the division of its nucleus. Section 1 Cellular Growth

Mitosis and Cytokinesis Cellular Reproduction The Stages of Mitosis  Prophase  The cell’s chromatin tightens and coils forming discrete chromosomes.  Sister chromatids are attached at the centromere.  Spindle fibers form in the cytoplasm. Section 2

Cellular Reproduction  The nuclear envelope and nucleolus seems to disappear.  Spindle fibers attach to the sister chromatids at centromere.  Whole structure including aster, centrioles, and spindle fibers is called the spindle apparatus Section 2 Mitosis and Cytokinesis

Cellular Reproduction Metaphase  Sister chromatids are pulled along the spindle apparatus toward the center of the cell  They line up in the middle of the cell (equator/metaphase plate). Section 2 Mitosis and Cytokinesis

Cellular Reproduction Anaphase  The microtubules of the spindle apparatus begin to shorten.  This causes sister chromatids separate into two identical chromosomes.  The chromosomes move toward the poles of the cell. Section 2 Mitosis and Cytokinesis

Cellular Reproduction Telophase  The chromosomes arrive at the poles and begin to relax/decondense.  Two new nuclear membranes begin to form and the nucleoli reappear.  The spindle apparatus disassembles. Section 2 Mitosis and Cytokinesis

Cellular Reproduction Cytokinesis  In animal cells, microfilaments constrict, or pinch, the cytoplasm. This area of constriction is called the cleavage furrow  In plant cells, a new structure forms b/w the two daughter nuclei, called a cell plate.(formation of cell wall) Section 2 Mitosis and Cytokinesis  Process that divides the cytoplasm and final step in cell division

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Prokaryotes Divide by binary fission –DNA duplicates and attach to P.M. –P.M. grows and pulls DNA molecules apart –Fission is completed w/formation of two new prokaryotic cells Section 2

Cell Cycle Regulation Cellular Reproduction Normal Cell Cycle  Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle. Section 3

Cellular Reproduction Quality Control Checkpoints  The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.  Spindle checkpoints also have been identified in mitosis. Section 3 Cell Cycle Regulation

Cellular Reproduction Contact Inhibition Contact inhibition is a growth mechanism, designed to keep cells growing into a layer one cell thick: a monolayer. If a cell has plenty of free space, it replicates rapidly and moves freely. This process keeps happening until the cells have divided so many times there is no longer any room in the layer for them to replicate. At this point, normal cells will stop replicating. Section 3 Cell Cycle Regulation

Cellular Reproduction Abnormal Cell Cycle: Cancer  Cancer is the uncontrolled growth and division of cells.  Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function. Section 3 Cell Cycle Regulation

Cellular Reproduction Causes of Cancer  The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.  Various environmental factors can affect the occurrence of cancer cells. Section 3 Cell Cycle Regulation

Cellular Reproduction Apoptosis  Programmed cell death  Cells going through apoptosis actually shrink and shrivel in a controlled process. Section 3 Cell Cycle Regulation

Cellular Reproduction Stem Cells  Unspecialized cells that can develop into specialized cells when under the right conditions Section 3 Cell Cycle Regulation

Cellular Reproduction Embryonic Stem Cells  After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized. Section 3 Cell Cycle Regulation

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  Less controversial because the adult stem cells can be obtained with the consent of their donor Section 3 Cell Cycle Regulation