Growth of Cells The growth of a cell depends on two things: Size or volume of individual cells Cell type and location in the body Individual cells grow as a result of assimilation. Assimilation occurs when a cell takes in digested food to make new protoplasm and the cell forms more complex substances from simpler ones.

Irritability Irritability is a cell’s ability to respond to changes in it’s environment. Examples of how a cell can respond are: Increase in size Transmission of chemical messages Cell division

Cell Cycle When most cells’ ‘life’ ends, they divide by mitosis and 2 new daughter cells form Stages in a eukaryotic cell’s life cycle with significant events: Interphase (DNA replication & growth), Mitosis (nuclear division) and Cytokinesis (cytoplasmic division)

Interphase Interphase is the growth period of the cell when it is not actively dividing (NOT a part of mitosis). During interphase the cell grows, makes new organelles, and replicates DNA. PPT PPT

DNA Replication Enzymes & proteins play key roles in replicating the DNA molecule Complementary base pairing (adenine-thymine and guanine-cytosine) maintain DNA’s structure This is when mutations occur.

Cell Division The steps of mitosis are: Prophase, Metaphase, Anaphase, and Telophase. Cytokinesis is the last part and often considered a separate phase – separation of cytoplasm and forming 2 new cells. Please make another taco. Please make Anna terrible. Etc, etc.

Prophase During prophase the chromatin in the nucleus condenses into chromosomes and spindles appear. The nucleolus and nuclear membrane disappear.

Metaphase During metaphase the chromatids separate. The chromosomes line up along the center of the cell and the centrioles move to the poles.

Anaphase Centrioles are divided during anaphase and chromatids are pulled toward the poles of the cell. The cell membrane also begins to indent at the equator of the cell.

Telophase The final stage of actual nucleus division is telophase. During telophase the cell membrane completely divides into two new daughter cells.

Cytokinesis Division of cytoplasm & formation of two new daughter cells, the cell membrane begins to indent at the equator of the cell during anaphase. Cleavage furrow forms at equator, gradually pinches off, leaving two cells.

Cell Pathology Tissues are formed by cell divisions. When the regulating factors for cell division cease to work cells may begin to divided rapidly in an abnormal manner. These cells compete with normal cells for resources and eventually cause the normal cells to die this is called cancer. Watch Cell Cycle & Cancer video. Some people lack genes for TRP (tumor regulating proteins) & are more susceptible to cancer development. Carcinogenic substances also cause cancer.