Biology

Chapter 5.1Cell Growth and Division

Biology presentations

• Show flim clip link miosis 1

Vocabulary

• Divide---to separate• Duplicate—an identical copy• Double—to increase two fold• Copy—reproduction of an orignial

• Example: cells DOUBLE their DNA in order to DIVIDE and create two nearly identical COPIES.

The cell cycle has four main stages.

• The cell cycle is a regular pattern of growth, DNA replication, and cell division.

• The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis.– Gap 1 (G1): cell growth and normal

functions

• Mitosis occurs only if the cell is large enough and the DNA undamaged.

– DNA synthesis (S): copies DNA

– Gap 2 (G2): additional growth

– Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)

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Cells divide at different rates.

• The rate of cell division varies with the need for those types of cells.

• Some cells are unlikely to divide (G0).

Question?

• Do you think a skin cell would have a long or short G1 stage?

• A skin cell would probably have a short G1 stage. Skin cells undergo a lot of wear and tear because they are exposed on the outside of the body.

Do cells have a limit for size?

Cell size is limited.

• Volume increases faster than surface area.

• Surface area must allow for adequate exchange of materials.

– Cell growth is coordinated with division.– Cells that must be large have unique shapes.

• Which has the larger ratio of surface area?• Cell 3• Which cell has the largest surface area to volume ratio?• Cell 1