Download 5.1 The Cell Cycle

5.1 The Cell Cycle
KEY CONCEPT
Cells have distinct phases of growth, reproduction,
and normal functions.
5.1 The Cell Cycle
Objectives
• Describe the stages of the cell cycle.
• Compare rates of division in different cell types.
• Identify factors that limit cell size.
5.1 The Cell Cycle
Vocabulary
• Cell Cycle
– Pattern growth, DNA replication, and cell division that
occurs in a eukaryotic cell.
• Mitosis
– Process by which a cell divides it nucleus and
contents.
• Cytokinesis
– Process by which the cell cytoplasm divides.
5.1 The Cell Cycle
The cell cycle has four main stages.
• The cell cycle is a regular pattern of growth, DNA
replication, and cell division.
5.1 The Cell Cycle
• The main stages of the cell cycle are gap 1, synthesis, gap
2, and mitosis.
– Gap 1 (G1): cell growth and
normal functions
– 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)
• Mitosis occurs only if the cell is large enough and the DNA
undamaged.
5.1 The Cell Cycle
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).
5.1 The Cell Cycle
Cell size is limited.
• Volume increases faster than surface area.
5.1 The Cell Cycle
• Surface area must allow for adequate
exchange of materials.
– Cell growth is coordinated with
division.
– Cells that must be large have
unique shapes.
5.1 The Cell Cycle
Question/Answer
• What are the four main stages of the cell cycle?
– Gap 1, synthesis, Gap 2, mitosis
• What can you infer about the relative amount of time a
cell spends in each stage?
– An actively dividing cell spends the least amount of
time in the mitosis stage. The length of Gap 1 varies
the most and is usually the longest.
• Do you think a skin cell would have a long or short G1
stage? Explain why.
– A skin cell would probably have a short G1. Skin cells
undergo a lot of wear and tear because they are
exposed on the outside of the body. Therefore, they
are probably replaced quickly.
5.1 The Cell Cycle
Question/Answer
• Which has the larger ratio of surface area to volume, a
tennis ball or a soccer ball? Explain your reasoning.
– A tennis ball, because volume increases more rapidly
than does surface area as a ball gets larger.