The Cell Cycle: Phases, Division Rates, and Cell Size Limit

1. KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. Immortal lung cancer cells

2. Objectives for section 5-1 • Detail the four main stages of the cell cycle. • Describe how cells divide at different rates. • Explain why cell size is limited.

3. The Cell Cycle -Cell division prevents cell from becoming too large -For growth and healing certain injuries Zebra Book Chapter 9

4. The cell cycle has four main stages. • The cell cycle is a regular pattern of growth, DNA replication, and cell division.

5. Interphase: stage during which cell grows, carries out cellular functions, and replicates -Cell spends 90% of time in interphase

6. Three stages of interphase -First stage - G1 (gap 1) • cell growth, normal functions, and preparing to replicate DNA • Nerve and brain cells stay in this phase

7. Second Stage - DNA synthesis (S) -Cell copies its DNA in preparation for cell division

8. Third Stage – Gap 2 (G2) • Additional growth as cell prepares for division of its nucleus in mitosis

9. The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. • 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.

10. 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).

11. Cell Size • 100 TRILLION cells in human body!! • Small but why? -Function more efficiently than large cells. Why??? HOMEOSTASIS!!

12. All substances that enter or leave a cell MUST cross cell surface • Substance do NOT need to travel as far to reach center of small cell Example: Pizza delivery

13. Cell size is limited. • Volume increases faster than surface area. • High surface area to volume ratio = small cells

14. Transport of Substances • Diffusion over large distances is slow and inefficient • Surface area must allow for adequate exchange of materials. • Small cells maintain more efficient transport systems Cytoskeleton (yellow) aids in transportation

15. Cellular Communications • Need for signaling proteins to move throughout cell also limits cell size • Cell size affects ability of cell to communicate instructions for cellular functions • Think of “telephone” game

16. Cell growth is coordinated with division. • Cells that must be large have unique shapes. Neurons R.B.C.s

17. Quick Quiz Time • Each question will be worth 2 points • You may NOT talk and/or communicate with a classmate • Scores will be collected and recorded at the end of the chapter

18. 1. Which of the following phrases best describes cytokinesis? • Division of the cytoplasm • Division of the nucleus • Division of DNA • Division of surface area

19. 2. During the gap 1 stage of the cell cycle, a cell • splits into two new cells. • carries out its normal functions. • duplicates its DNA. • divides its cytoplasm

20. 3. Which of the following limits the maximum size of a cell? a. the stage of the cell cycle b. the ratio of cell surface area to volume c. the number of mitochondria in the cell d. the size of the organism

21. Trade your paper with a non-lab partner

22. 1. Which of the following phrases best describes cytokinesis? • Division of the cytoplasm • Division of the nucleus • Division of DNA • Division of surface area

23. 2. During the gap 1 stage of the cell cycle, a cell • splits into two new cells. • carries out its normal functions. • duplicates its DNA. • divides its cytoplasm

24. 3. Which of the following limits the maximum size of a cell? a. the stage of the cell cycle b. the ratio of cell surface area to volume c. the number of mitochondria in the cell d. the size of the organism

25. End of Show