1. Cell Growth and Reproduction Cell Cycle

2. Growth in Organisms For an organism to grow, its cells divide instead of getting larger.

3. Cell Size Limitations 1) Diffusion: If organelles are too far from the cell membrane, they would have to wait a long time to get molecules that are diffusing through (ex. lysosomes, mitochondria).

4. Cell Size Limitations DNA: The nucleus cannot provide DNA fast enough to act as the blue print for the high amounts of proteins and enzymes that a large cell would need. (ex. cytoskeleton).

5. Cell Size Limitations Surface area-to-volume ratio: The volume of the cell increases a lot faster than the surface area. Therefore if the cell gets too big, the cell membrane will not have enough surface area to diffuse the amount of nutrients the cell needs or get rid of the waste the cell produces 1mm 2mm 4mm Surface area =6mm2 Surface area= 24mm2 Surface area= 96mm2 Volume= 1mm3 Volume = 8mm3 Volume= 64mm3

6. Cell Cycle Cell cycle – stages that the cell goes through from growth to repair to division.

7. Interphase Interphase- period where the cell is preparing to divide through growth and maintenance. (90% of a cells life). –G 1 phase (“first gap”) growth –S phase (“synthesis”) DNA duplication –G 2 phase (“second gap”) Maintenance

8. Synthesis Synthesis – portion of interphase where cells duplicate their DNA. DNA is packaged into sets of chromosomes. Humans have 46 chromosomes (23 from each parent)

9. Synthesis cont’d Somatic cells normal body cells, have two sets of chromosomes (diploid 2n) Gametes reproductive cells (sperm and eggs) only have one set of chromosomes (haploid n)

10. Synthesis cont’d In synthesis each chromosome gets copied and is attached to its copy. Sister chromatids – identical copies of a chromosome Centromere – holds sister chromatids together. -At this point their are double the number of chromosomes

11. Mitosis Mitosis - Cell division where 1 diploid parent cell makes 2 identical diploid daughter cells. **** Technically mitosis id the division of one nucleus into two. Parent cell Sister chromatids chromosomes identical daughter cells

12. Prophase the chromosomes coil up and become visible while the nuclear envelope disappears. Sister chromatids are present. A centriole forms at each pole and spindle fibers made of microtubules grow out. Short microtubules stick out from the centriole in a star shape known as an aster.

13. Metaphase Early in metaphase (prometaphase) spindle fibers attach to each of the chromatids at a sight called the kinetochore. The spindle fibers line the chromatids up at the equator of the cell called the metaphase plate. Kinetochore

14. Fig. 12-7 Microtubules Chromosomes Sister chromatids Aster Metaphase plate Centrosome Kinetochores Kinetochore microtubules Overlapping nonkinetochore microtubules Centrosome 1 µm 0.5 µm

15. Anaphase Anaphase- During this phase, the kinetochores “reel in” or “gobble up” the spindle fibers to pull the sister chromatids apart by splitting their centromere. The split chromatids are pulled towards opposite poles of the cell

17. Telophase Once the chromatids have reached the opposite sides the spindle fibers disappear, the chromosomes unravel, and the nuclear envelope reappears on the two new nuclei. In cytokinesis, the cytoplasm then forms a cleavage furrow at the equator to split the cytoplasm. (in plants a cell plate forms at the equator.)**** Two identical daughter cells are formed

19. MitosisMitosis Vid Mitosis **

20. Fig. 12-UN2

21. Binary Fission Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission. (believed that mitosis may have evolved from binary fission) In binary fission, the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22. Fig. 12-11-4 Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane Cell wall Origin

23. Cytoplasmic Signals The cell cycle is controlled by chemical signals in the cytoplasm Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Fig. 12-13 Experiment 1 Experiment 2 EXPERIMENT RESULTS SG1G1 M G1G1 M M S S When a cell in the S phase was fused with a cell in G 1, the G 1 nucleus immediately entered the S phase—DNA was synthesized. When a cell in the M phase was fused with a cell in G 1, the G 1 nucleus immediately began mitosis—a spindle formed and chromatin condensed, even though the chromosome had not been duplicated.

25. The Cell Cycle Control System cell cycle control system- a set of events that occurs in a sequence to regulate the cell cycle. The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26. the G 1 checkpoint is the most important Most cells that make it past G 1 go on to divide. If the cell does not receive the go-ahead signal, it will go into a non-dividing state called the G 0 phase. (ex. Kinetochores didn’t attach correctly) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Cell Cycle Control System

27. Cyclin and Cdks cyclin – a regulatory protein that builds up in the G 2 phase. Cyclin dependent kinases (Cdks) – a regulatory protein that is always present waiting for the arrival of cyclin. MPF (maturation-promoting factor) - cyclin and Cdks combined to trigger a passage through G 2 and Mitosis. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. External Signals growth factors - proteins released by certain cells that stimulate other cells to divide platelet-derived growth factor (PDGF) stimulates the division of human fibroblast cells (connective tissue). This is released when cut from blood platelets so healing can begin.

30. density-dependent inhibition - crowded cells stop dividing anchorage dependence – cells must be attached to something in order to divide External Signals cont’d

31. Cancer Cells Cancer cells do not respond normally to the cells cycle check points or external signals. Cancer cells may not need growth factors to grow and divide: –They may make their own growth factor –They may convey a growth factor’s signal without the presence of the growth factor –They may have an abnormal cell cycle control system Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

32. Transformation - A normal cell is converted to a cancerous cell If the cancer stays at the original site, the lump is called a benign tumor Malignant tumors spread to surrounding tissues through metastasis (transport by blood vessels.) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Transformation

33. You should now be able to: 1.Describe the organization eukaryotic genome. 2. List the phases of the cell cycle; describe the sequence of events during each phase 3.List the phases of mitosis and describe the events characteristic of each phase 4.Draw the phases of mitosis and describe the structures and events in each phase. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. 5.Compare and contrast cytokinesis in animals and plants 6.Describe the process of binary fission in bacteria. 7.Describe cytoplasmic signaling and checkpoints as well as external signaling of cells. 8.Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls 9.Distinguish between benign and malignant tumors. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings