1 10-1: Cell Growth

2 Suppose this library was located in a small town. People came and borrowed books, returned them, borrowed more, used the computers there, and enjoyed family programs offered there. What problems would arise for the library if that town started to grow in population?

3 This cell is like a town and the DNA is a lot like a library. It stores information that is used for many purposes. If the cell got bigger and bigger, the demand on the DNA would get bigger and bigger. Eventually the DNA would not be able to handle the demand.

4 Suppose this two-lane main street was located in a small town. People use this street to go to their favorite stores and restaurants. What problems would arise if this town started to grow into a tourist attraction and more and more people started to visit places on this street?

5 A cell would encounter similar problems as the two lane road in town. Materials would run into more “traffic” inside the cell and it would be difficult to get things from one place in a cell to another.

6 Why do cells divide and not continue to grow? There are 2 main reasons: Reason #1 The larger the cell grows, the more demands the cell places on the DNA. Reason #2 The cell has more trouble moving nutrients and wastes across the cell membrane.

Before a cell becomes too large, it divides and forms two “daughter cells.” 7 What is Cell Division? What is Cell Division?

8 Why are chromosomes not visible in most cells except during cell division? Because the genetic material is spread throughout the nucleus.

9 Draw and label a chromosome. Chromatid- two identical halves of a chromosome. Centromere- area where chromatids attach to each other.

10 What is the organelle located near the nucleus that helped with cell division? (chapter 7) centriole

Cell Division: Problems Solved! Before the cell divides, it copies it’s DNA to give a complete set of genetic information to each daughter cell. Each new daughter cell has an increased ratio of surface area to volume which allows sufficient exchange of materials across the cell membrane. 11

12 Do the Math! Surface area= (length x width) x number of sides Volume= length x width x height Ratio = Surface Area: Volume, then reduce it like a fraction. 6: 1 24: 8, 3:1 54:27, 2:1

13 Preview what Chapter 10 is all about!

:Cellular Division

15 Cell Division All cells are derived from pre- existing cells All cells are derived from pre- existing cells New cells are produced for growth and to replace damaged or old cells New cells are produced for growth and to replace damaged or old cells New cells are genetically identical to the original cells. New cells are genetically identical to the original cells.

16 Identical Daughter Cells Parent Cell Two identical daughter cells

Chromosomes’ Role in the Process As the cell divides, the “sisters” separate and one strand goes to each new cell. 17

18 The Cell Cycle

19 Five Phases of the Cell Cycle 1) G 1 - primary growth phase 2) S – synthesis; DNA replicated 3) G 2 - secondary growth phase collectively these 3 stages are called interphase 4) M – mitosis 5) C- cytokinesis

20 Cell Cycle

21 Cell Cycle Draw and label it in a different way:

22 Interphase - G 1 Stage 1 st growth stage after cell division 1 st growth stage after cell division Cells mature by making more cytoplasm & organelles Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities- Cell carries on its normal metabolic activities- examples-animal cell:cellular respiration, plant cell: photosynthesis

23 Interphase – S Stage Synthesis stage Synthesis stage DNA is copied or replicated DNA is copied or replicated Two identical copies of DNA Original DNA

24 Interphase – G 2 Stage 2 nd Growth Stage 2 nd Growth Stage Occurs after DNA has been copied Occurs after DNA has been copied All cell structures needed for division are made (example: centrioles) All cell structures needed for division are made (example: centrioles) Both organelles & proteins are completed and cell is ready to divide. Both organelles & proteins are completed and cell is ready to divide.

:Regulating the Cell Cycle

Regulating the Cell Cycle There are differences in the rate at which cells grow and divide. Example: Skin Cells vs. Nerve Cells 26

Cell Cycle Regulators Cyclin- Protein within a cell that regulates the timing of the cell cycle in eukaryotes. There are two types of these proteins: 1) internal regulators- things must happen in order within the cell! 2) external regulators- direct the speed at which the cycle occurs! 27

28 What is cancer and why does it happen? Cancer- cells that do not respond to the signals that regulate growth and form tumors.

29 Let’s hear a little more about the cell cycle and cancer…

30 10:2 (cont.) Mitosis

31 Parts of a Dividing Cell

32 Mitosis Defined Division of the nucleus Division of the nucleus Only occurs in eukaryotes Only occurs in eukaryotes Has four stages Has four stages Doesn’t occur in some cells such as brain cells Doesn’t occur in some cells such as brain cells

33 Four Mitotic Stages Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase

34 Prophase First and longest stage of Mitosis. First and longest stage of Mitosis. Chromatin in nucleus condenses to form visible chromosomes Chromatin in nucleus condenses to form visible chromosomes Spindle- microtubule structure that helps separate chromosomes forms Spindle- microtubule structure that helps separate chromosomes forms

35 Prophase Centrioles begin to separate to opposite sides (poles) of the cell. Centrioles begin to separate to opposite sides (poles) of the cell. Nuclear membrane & nucleolus are broken down Nuclear membrane & nucleolus are broken down Chromosomes continue condensing & are clearly visible Chromosomes continue condensing & are clearly visible

36 Prophase Pictures Prophase Pictures

37 Metaphase 2 nd phase of Mitosis 2 nd phase of Mitosis Chromosomes move to the center of the cell and line up along the equator. Chromosomes move to the center of the cell and line up along the equator. Spindle fibers attach to the centromere of each chromosome Spindle fibers attach to the centromere of each chromosome Spindle finishes forming between the poles of the cell Spindle finishes forming between the poles of the cell

38 Metaphase Pictures Chromosomes lined at the Equator Spindle Fibers

39 Anaphase 3 rd phase of Mitosis 3 rd phase of Mitosis Cell becomes stretched Cell becomes stretched Sister chromatids are pulled apart as the centromere splits. Sister chromatids are pulled apart as the centromere splits. “sisters” become individual chromosomes “sisters” become individual chromosomes Anaphase is over when chromosomes stop moving. Anaphase is over when chromosomes stop moving.

40 Anaphase Pictures Sister Chromatids being separated

41 Telophase 4 th phase of Mitosis 4 th phase of Mitosis Sister chromatids at opposite poles Sister chromatids at opposite poles Spindle disassembles Spindle disassembles Nuclear envelope forms around each set of sister chromatids Nuclear envelope forms around each set of sister chromatids Nucleolus reappears Nucleolus reappears Cell is indented (figure 8) Cell is indented (figure 8)

42 Telophase Pictures

43 Cytokinesis Division of cytoplasm and cell into two, identical halves called daughter cells Division of cytoplasm and cell into two, identical halves called daughter cells Usually happens at the same time as telophase. Usually happens at the same time as telophase. In plant cells, cell plate forms at the equator to divide cell In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell In animal cells, cleavage furrow forms to split cell

44 Cytokinesis Pictures Cleavage furrow in animal cell Cell plate in plant cell

45 Daughter Cells of Mitosis Have the same number of chromosomes as each other and as the parent cell from which they were formed Have the same number of chromosomes as each other and as the parent cell from which they were formed Identical to each other, but smaller than parent cell Identical to each other, but smaller than parent cell Must grow in size to become mature cells (G 1 of Interphase) Must grow in size to become mature cells (G 1 of Interphase)

46 Review of Mitosis

47 Mitosis Animation Name each stage as you see it occur?

48 Interphase Prophase Metaphase Anaphase Telophase Name the Mitotic Stages:

49 Name the Stages of Mitosis: Interphase Early prophase Mid-Prophase Late Prophase Metaphase Late Anaphase Early Anaphase Early Telophase, Begin cytokinesis Late telophase, cytokinesis

50 Identify the Stages Early, Middle, & Late Prophase Late Prophase MetaphaseAnaphase Late Anaphase Telophase Telophase & Cytokinesis