Chapter 8.2 – Cell Growth and Reproduction

1. Chapter 8.2 – Cell Growth and Reproduction

2. Cell Size Limitation • The cells that make up a multicellular organisms come in a wide variety of shapes and sizes. • The smallest cell is the book mentions is the red blood cell and the largest cell is the yolk of an ostrich egg.

3. Diffusion limits cell size • The plasma membrane allows nutrients to enter the cell and wastes to leave. • Nutrients and waste move by diffusion. • Although diffusion is a fast and efficient process over short distances, it becomes slow as the distances becomes larger. • Because of the slow rate of diffusion, organisms can’t be just one giant-sized cell.

4. Section 8.2 Summary – pages 201 - 210 Surface area-to-volume ratio 4 mm 4 mm 2 mm 1 mm 2 mm 1 mm 1 mm 2 mm Surface area = 6 mm2 Volume = 8 mm3 4 mm Surface area = 24 mm2 Volume = 8 mm3 • As a cell’s size increases, its volume increases much faster than its surface area.

5. Question: Why do you think we are made up of small sized cells? • Cells divide before they become too large in order to continue to function properly.

6. Cell Reproduction • Cell division is the process by which new cells are produced from one cell. • Cell division results in two cells that are identical to the original. • Early biologists observed that just before cell division, several short stringy structures suddenly appeared in the nucleus.

7. These structures which contain DNA are called chromosomes. • For most of the cells lifetime, chromosomes exist as chromatin, long strands of DNA. • Before a cell can divide, the long strands of chromatin must be reorganized into a chromosome

8. Section 8.2 Summary – pages 201 - 210 The structure of eukaryotic chromosomes Centromere Sister chromatids Supercoil within chromosome Chromosome Continued coiling within supercoil Histone H1 Nucleosome DNA

9. Video of Cell Cycle

10. The Cell Cycle • The cell cycle is the sequence of growth and division • The majority of a cells life is spent in Interphase. • During Interphase 2 things happen: 1. A cell grows in size 2. Chromosomes are duplicated in preparation for cell division. Interphase

11. Section 8.2 Summary – pages 201 - 210 Interphase: A Busy Time • Interphase, the busiest phase of the cell cycle, is divided into three parts. Interphase DNA synthesis and replication Centrioles replicate; cell prepares for division Rapid growth and metabolic activity

12. Mitosis • Mitosis is the process by which two daughter cells are formed, each containing a complete set of chromososmes. • What two parts make up the bulk of the cell cycle? • 1. Cell division • 2. Mitosis

13. The Phases of Mitosis • Prophase Prepare for cell division • Metaphase Middle (chromosomes) • Anaphase Away (chromosomes) • Telophase Two new cells formed

14. Prophase • Nucleus begins to disappear • Centrioles go to opposite ends of the poles(see picture) • As centrioles move to opposite ends of the cell, the spindle begins to form between them.

15. Prophase: The first phase of mitosis Section 8.2 Summary – pages 201 - 210 • The chromatin turns into visible chromosomes • (Draw and label Figure 8.12) Sister chromatids Centromere Spindle fibers Disappearing nuclear envelope Doubled chromosome

16. Metaphase: The second stage of mitosis Section 8.2 Summary – pages 201 - 210 • Chromosomes move toward the middle of the cell. • * Draw a picture of the cell in Metaphase (207) Centromere Sister chromatids

17. Anaphase: The third phase of mitosis Section 8.2 Summary – pages 201 - 210 • Chromosomes move away from the middle and goes toward opposite ends of the cell. • * Draw a picture of the cell in Anaphase (207)

18. Telophase: The fourth phase of mitosis Section 8.2 Summary – pages 201 - 210 • During telophase, two distinct daughter cells are formed. The cells separate as the cell cycle proceeds into the next interphase. • The formation of two new cells. • *Draw a picture of the cell in Telophase (207) Nuclear envelope reappears Two daughter cells are formed

19. Cytokinesis: • Following telophase, the cell’s cytoplasm divides in a process called cytokinesis.

20. Section 8.2 Summary – pages 201 - 210 Cytokinesis • Following telophase, the cell’s cytoplasm divides in a process called cytokinesis. • Cytokinesis differs between plants and animals. • Toward the end of telophase in animal cells, the plasma membrane pinches in along the equator.

21. Section 8.2 Summary – pages 201 - 210 Cytokinesis • Plant cells have a rigid cell wall, so the plasma membrane does not pinch in. • A structure known as the cell plate is laid down across the cell’s equator. • A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete.

22. Section 2 Check Question 1 The stringy structures in the cell nucleus that contain DNA are __________. (TX Obj 2; 4B) A. centromeres B. chromosomes C. genes D. chlorophylls

23. Section 2 Check The answer is B. Chromosomes are the carriers of the genetic material of the cell. A gene is a segment of DNA that controls the production of a protein.

24. Section 2 Check Question 2 Look at the diagram and identify the stage of mitosis that is depicted. (TX Obj 2; 4B) Centromere Sister chromatids A. prophase C. anaphase B. metaphase D. telophase

25. Section 2 Check The answer is B. Metaphase is the short second phase of mitosis, during which the chromosomes begin to line up on the equator of the spindle. Centromere Sister chromatids

26. Section 2 Check Question 3 What is the process by which a cell's cytoplasm divides? (TX Obj 2; 4B) A. cytokinesis B. telekinesis C. meiosis D. mitosis

27. Section 2 Check The answer is A. Cytokinesis follows telophase and allows the two new cells to separate.

28. Section 2 Check Question 4 In multicellular organisms, groups of cells that work together to perform a specific function are called __________. (TX Obj 2; 10B) A. organ systems B. organs C. tissues D. cell cycles

29. Section 2 Check The answer is C. Tissues organize to form organs, which work with other organs to form organ systems.