Click on a lesson name to select. Chapter 9 Cellular Reproduction Section 1: Cellular Growth Section 2: Mitosis and Cytokinesis Section 3: Cell Cycle Regulation

9.1 Cellular Growth Objectives: 1.Explain why cells are relatively small. 2.Summarize the primary stages of the cell cycle. 3.Describe the stages of interphase.

9.1 Cellular Growth Main Idea – Cells grow until they reach their size limit, then they either stop growing or divide.

1. Most cells are smaller than the period at the end of this sentence. 2. The key factor that limits the size of a cell is the ratio of its surface area to its volume.

3. The surface area of the cell is the area covered by the plasma membrane. To calculate the surface area of the cube multiply L x W x number of sides (6)

4. The volume refers to the space taken up by the contents of the cell. To calculate the volume, multiply L x W X H 5. As a cell grows, it’s volume increases more rapidly than the surface area. As a cell increases in size the surface area to volume decreases

9.1 Cellular Growth Ratio of Surface Area to Volume Chapter 9 Cellular Reproduction

6.If a cell is too large it may have difficulty supplying nutrients and expelling waste products. 7.Cells remain small to maximize the ability of diffusion and motor proteins to transport nutrients and waste products.

8.Small cells maintain more efficient transport systems. 9. The need for signaling proteins to move throughout the cell also limits cell size. 10. Cell size affects the ability of the cell to communicate instructions for cellular functions.

11.Cells reproduce by a cycle of growing and dividing.

12.There are three main stages of the cell cycle interphase, mitosis, and cytokinesis. In the cell cycle, a cell stays in Interphase the longest

Diagram of cell cycle – see pg. 246 InterphaseLongest phase Cell grows DNA replication occurs MitosisNucleus divides Occurs in 4 stages CytokinesisShortest phase Cytoplasm divides

 Interphase is the stage during which the cell grows, carries out cellular functions, and replicates.  Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. Cellular Reproduction Chapter Cellular Growth  Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.

13. The duration of the cell cycle varies, depending on the cell that is dividing. 14.For most normal, actively dividing animal cells, the cell cycle takes approximately hours.

15. During interphase, the cell grows, develops into a functioning cell, duplicates it’s DNA, and prepares for division.

16.Interphase is divided into 3 stages G 1, S, G 2.

17. Chromosomes – contain genetic material. Chromatin – relaxed form of DNA in nucleus copies it’s DNA in preparation for cell division.

18. In mitosis, the cell’s nuclear material divides and separates into opposite ends of the cell. 19. In cytokinesis, the cell divides into 2 daughter cells, with identical nuclei.

20. The cell cycle is the method by which eukaryotic cells reproduce themselves. 21. Prokaryotic cells, reproduce by a method called binary fission.

9.2 Mitosis and Cytokinesis Objectives: 1.Describe the events of each stage of mitosis. 2.Explain the process of cytokinesis. Main Idea Eukaryotic cells reproduce by mitosis, the process of nuclear division, and cytokinesis, the process of cytoplasm division.

Mitosis 1.The key activity of mitosis is the accurate separation of the cell’s replicated DNA. 2.The process of mitosis increases the number of cells as a young organism grows to its adult size. 3.Organisms also use mitosis to replace damaged cells.

The Stages of Mitosis 4. The 4 stages of mitosis are: prophase, metaphase, anaphase and telophase.

9.2 Mitosis and Cytokinesis Cellular Reproduction The Stages of Mitosis  Prophase- the first stage of mitosis—cell spends most of its time here Chapter 9

5. Chromatin tightens or condenses into chromosomes. This action facilitates chromosome movement. 6. As prophase continues, the nucleolus seems to disappear.

7. Microtubule structures called spindle fibers form in the cytoplasm. 8. Near the end of prophase, the nuclear envelope disappears.

Cellular Reproduction Metaphase 9. Sister chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell and line up in the middle, or equator of the cell. Chapter Mitosis and Cytokinesis

Cellular Reproduction Anaphase 11. At the end of anaphase, the microtubules, with the help of motor proteins, move the chromatids toward the poles of the cell. Chapter Mitosis and Cytokinesis 10. The chromatids are pulled apart.

Cellular Reproduction Telophase 12. Chromosomes arrive at the poles of the cell and begin to relax or decondense. 13. Two new nuclear membranes begin to form and the nucleoli reappear. Chapter Mitosis and Cytokinesis

Cytokinesis – process that divides the cytoplasm 14. This results is 2 cells, each with identical nuclei.

15. In animal cells, cytokinesis is accomplished by using microfilaments to constrict or pinch the cytoplasm.

16. In plant cells, a new structure called a cell plate forms between two daughter cells. Cell walls then form on either side of the cell plate.

The 4 Stages of Mitosis Prophase – “poles form” (centrioles) chromosomes condense; spindle forms Metaphase – “meet in the middle” chromosomes line up at the equator Anaphase – “pull apart” chromosomes move to opposite poles Telophase – “pinch together” nuclear envelope forms; chromosomes decondense

Remember the Stages of Cell Division IInterphase ProbablyProphase MakeMetaphase AAnaphase TeacherTelophase CrazyCytokinesis

Prokaryotic cells undergo binary fission- cell divides into 2 genetically identical cells WHY? Prokaryotic cells do not have a nucleus. Mitosis is division of the nucleus.

Binary Fission - lhs.lps.org

2. Mitosis ProphaseNuclear membrane disintegrates; chromosomes condense MetaphaseChromosomes attach to spindle and line up at the equator of cell AnaphaseChromosomes move apart to opposite poles TelophaseCell pinches together; Chromosomes relax

9.3 Cell Cycle Regulation Objectives: 1.Summarize the role of cyclin proteins in controlling the cell cycle. 2.Explain how cancer relates to the cell cycle. 3.Describe the role of apoptosis. 4.Summarize the two types of stem cells and their potential uses. Main Idea - The normal cell cycle is regulated by cyclin proteins.

CELL DIVISION GENES The rate of cell division varies depending on the type of cell. Some cells divide frequently (some human skin cells divide once/hour) Some cells divide occasionally (liver cells divide about once/year) Some cells don’t divide once they form (nerve cells)

1.A mechanism involving proteins and enzymes control the cell cycle.

2. These proteins are called cyclins because they regulate the timing of the cell cycle in eukaryotic cells.

3. Cyclins bind to enzymes called cyclin-dependent kinases(CDKs) to start various activities that take place in the cell cycle.

4. Cyclin/CDK combinations occur only during the stages of interphase and mitosis.

5. Different cyclins/CDK’s combinations control different activities at different stages in the cell cycle.

6. The different cyclin/CDK combinations signal the start of the cell cycle, DNA replication, protein synthesis, nuclear division and the end of the cell cycle.

7. The cell cycle also has built in checkpoints that monitor the cycle and can stop it if something goes wrong.

Cell Cycle with checkpoints

Cellular Reproduction 8.Checkpoints occur at the end of G1, during the S stage, in the G2 stage and at beginning of mitosis. Chapter 9

Cellular Reproduction 9. When cells don’t respond to the normal cell cycle control mechanisms, a condition called cancer can result. Chapter Cell Cycle Regulation

10. Cancer is the uncontrolled growth and division of cells--a failure in the regulation of the cell cycle.

Cancer cells don’t stop when they touch nearby cells... they just keep growing! That’s what makes a tumor. NO CONTACT INHIBITION

Control of Cell Division Section 10-3 Cells grow until they touch other cells If center cells are removed, cells near the space will start to grow again. SHOWS: Cell division genes can be turned on and off Contact Inhibition

11. When unchecked, cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Comparison of Normal and Cancerous Stomach Cells

12. Cancer cells spend less time in interphase than do normal cells, which means cancer cells grow and divide unrestrained as long as they are supplied with essential nutrients.

Normal Stomach Cells –Interphase120 min. –Prophase 60 min. –Metaphase 10 min. –Anaphase 3 min. –Telophase 12 min. Cancerous Stomach Cells –Interphase 16 min. –Prophase15 min. –Metaphase 2 min. –Anaphase 1 min. –Telophase 3 min.

Cancer cells Don’t stop dividing Like a “car with no brakes” Can spread to new places (METASTASIS)

A. Causes of Cancer 13. The changes that occur in the regulation of cell growth and division of cancer cells are due to mutation or changes in the segments of DNA that control the production of proteins.

14. Mutations are permanent changes in a cell’s DNA; can cause changes in the growth of a cell leading to cancer.

15. Various environmental factors can affect the occurrence of cancer cells. 16. Substances and agents that are known to cause cancer are called carcinogens. Examples: Ultraviolet light, cigarette smoke, tobacco, x-rays, asbestos, some pesticides, arsenic, some viruses, etc.

B. Cancer genetics 17. More than one change in DNA is required to change an abnormal cell into a cancer cell.

18. The risk of cancer increases with age. Because, number of mutations increases with age. 19. The fact that multiple changes must occur also might explain why cancer runs in some families

20. When an embryo divides, some cells go through a process called apoptosis, or programmed cell death.

21. Examples of apoptosis occur during the development of human hand and foot; in plants, leaves falling from trees during autumn. 22. Apoptosis also occurs in cells that are damaged beyond repair including cells with DNA damage that could lead to cancer.

Stem cells – 23. The majority of cells in a multicellular organisms are designed for a specialized function. 24. Stem cells are unspecialized cells that can develop into specialized cells; 2 types Adult stem cells and Embryonic stem cells

Possible uses for stem cells

Embryonic stem cells 25. An embryo results from the fertilization of an egg by a sperm. These unspecialized cells are embryonic stem cells.

26. Embryonic stem cells research is controversial because of ethical concerns about the source of the cells. 27. Ethics are values in society that consider the rightness or wrongness of certain actions

Adult stem cells 28. Adult stem cells are found in various tissues in the body and might be used to maintain and repair the same kind of tissue in which they are found. 29. Research with adult stem cells is much less controversial because the adult stem cells can be obtained with the consent of their donor.