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 How long do our cells last?last?

In the human body our cells In the human body our cells last between two weeks (a skin last between two weeks (a skin cell) to cell) to 16 years (our muscles)16 years (our muscles)

Cell division occurs more Cell division occurs more rapidly in embryos and rapidly in embryos and childrenchildren

The Cell Cycle

InterphaseThe longest phase of the cell cycle

• G1 phase – the growth phase, organelles increase

in number, longest phase of interphase

• S phase – chromosomes are replicated

• G2 phase- cell continues to grow

What is a Chromosome?

MitosisThe Division of Chromosomes

Specifically the chromosomes

in somatic cells

ProphaseProphaseChromosomes shorten

and thicken

Nuclear membrane disappears

Spindle fibers form

Centrioles move to opposite poles

MetaphaseMetaphase

Chromosomes line up at equatorial plate

Attach to spindle fibers with centromere

AnaphaseAnaphase

• Chromosomes move towards poles

TelophaseTelophase

• Nuclear membrane forms around chromosomes

Cytokinesis

The division of the cytoplasm

The cell membrane forms between the two new identical daughter cells