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5.1 The Cell Cycle KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. 5.1 The Cell Cycle The cell cycle has four main stages. • Cell cycle-is the regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells. 5.1 The Cell Cycle • The 4 main stages of the cell cycle: • 1) Gap 1 (G1)- Cell carries out normal functions, increases in size, and organelles increase in number. Cells spend most of their life in this stage. • 2) Synthesis (S)- Cells make a copy of nuclear DNA. • 3) Gap 2 (G2)- Cells continue normal function and continue to grow. Cells must go through certain checkpoints, like size, number of organelles, DNA copied, etc. • 4) Mitosis (M)- Cell division stage. Consists of 2 stages: – A) Mitosis- Division of cell nucleus and its contents. – B) Cytokinesis- Process that divides cell cytoplasm, resulting in two identical daughter cells. 5.1 The Cell Cycle Cells divide at different rates. • The rate of cell division varies with the bodies need for those types of cells. – In human cells, S, G2, and M takes about 12 hours – Length of the G1 stage depends on cell type – Rate of division is greater in the embryo and kids • G0 stage- stage where some cells rarely, if ever, divide. Example Lymphocytes (White Blood Cells). 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.