Cell Reproduction Why do Cells Divide? Section 5-1, 5-2

Why must the cell divide? Nutrients and waste pass through the cell membrane When the cell membrane no longer has a large enough surface area to transport the volume of the cell It divides!

How long do our cells last?  In the human body our cells last between two weeks (a skin cell) to 16 years (our muscles)  Cell division occurs more rapidly in embryos and children

The Cell Cycle

Interphase The longest phase of the cell cycle G 1 phase – the growth phase, organelles increase in number, longest phase of interphase S phase – chromosomes are replicated G 2 phase- cell continues to grow

What is a Chromosome?

Mitosis The Division of Chromosomes Specifically the chromosomes in somatic cells

Prophase  Chromosomes shorten and thicken  Nuclear membrane disappears  Spindle fibers form  Centrioles move to opposite poles

Metaphase  Chromosomes line up at equatorial plate  Attach to spindle fibers with centromere

Anaphase Chromosomes move towards poles

Telophase Nuclear membrane forms around chromosomes

Cytokinesis The division of the cytoplasm The cell membrane forms between the two new identical daughter cells