Go to Section: Getting Through Materials move through cells by diffusion. Oxygen and food move into cells, while waste products move out of cells. How does the size of a cell affect how efficiently materials get to all parts of a cell? Work with a partner to complete this activity. Section On a sheet of paper, make a drawing of a cell that has the following dimensions: 5 cm x 5 cm x 5 cm. Your partner should draw another cell about one half the size of your cell on a separate sheet of paper. 2.Compare your drawings. How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell? 3.What is the advantage of cells being small?

Go to Section: Section Outline 10–1Cell Growth A.Limits to Cell Growth 1.DNA “Overload” 2.Exchanging Materials 3.Ratio of Surface Area to Volume 4.Cell Division Section 10-1

Go to Section: There are 2 main reasons why cells divide rather than growing larger: 1.DNA “Overload”-when a cell is small, the information stored in that DNA meets the needs of the cell; as a cell grows it usually does not make extra copies of DNA which created an information shortage. ex. Small town library Section 10-1

Go to Section: 2.Material Exchange-all food, water, oxygen and wastes must pass through the cell membrane. The rate at which this exchange takes place depends on the surface area of the cell. Ratio of Surface Area to Volume- Volume increases much more rapidly than the surface area, causing the ratio of surface area to volume to decrease. ex. Main street Section 10-1

Go to Section: Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume Ratio of Surface Area to Volume in Cells Section 10-1

Go to Section: Division of the Cell The process by which a cell divides into 2 new daughter cells. Before the cell divides, DNA replication takes place. These processes allow the cells to: a. Reduce volume b. Increase surface area to volume ratio c. Maintain available genetic information Section 10-1

Go to Section: Cell Cycle The cell cycle represents recurring events that take place in the period of time from the beginning of one cell division to the beginning of the next. In addition to cell division, the cell cycle includes periods when the cell is growing and actively producing materials it needs for the next division. Section Why is the cell cycle called a cycle? 2. Why do you think that it is important for a cell to grow in size during its cell cycle? 3. What might happen to a cell if all events leading up to cell division took place as they should, but the cell did not divide?

Go to Section: Section Outline 10–2Cell Division A. Chromosomes B. The Cell Cycle C. Events of the Cell Cycle D. Mitosis 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase E. Cytokinesis Section 10-2

Video 1

Go to Section: Chromosomes-are comprised of DNA and protein. These carry the genetic information in eukaryotic cells. Only visible during cell division. Before cell division, each chromosome is replicated, creating identical “sister” chromatids. During cell division each chromatid will go to the 2 new cells. Section 10-2

Go to Section: Cell Cycle- 1. Cell grows 2. Prepares for division 3. Divides to form 2 daughter cells 4. Daughter cells begin cycle again Section 10-2

Go to Section: M phase G 2 phase S phase G 1 phase Figure 10–4 The Cell Cycle Section 10-2

Go to Section: Interphase This phase consists of: G 1 phase-main growth of a cell S phase- DNA replicated G 2 phase-many organelles and molecules required for cell division are produced Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Mitosis part of eukaryotic cell division in which the nucleus divides Lasts a few minutes to several days. Four phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Section 10-2

Go to Section: Prophase This is the first and longest phase. Events that take place include: 1. chromosomes become visible 2. centrioles separate and move to opposite sides 3. spindle (fan-like microtubule structure) forms 4. chromosomes attach to spindle fibers Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Metaphase Second phase of mitosis Events that take place include: 1. chromosomes line up in the center of the cell 2. microtubules connect the centromere of each chromosome to the two poles of the spindle Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Anaphase Third phase of mitosis Events that take place include: 1. the centromeres that join the sister chromatids split allowing the sister chromatids to become individual chromosomes 2. chromosomes move towards the ends of the cell Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Telophase Fourth and final phase of mitosis Events that take place include: 1. chromosomes are at opposite ends of cell and lose shape 2. two new nuclear envelopes will form around the chromosomes Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Cytokinesis Animal cells-cell membrane is drawn inward until the cytoplasm is pinched into 2 equal parts Plant cells-a cell plate forms midway between the divided nuclei. This eventually becomes a cell membrane and a cell wall. Section 10-2

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: includes is divided into Concept Map Section 10-2 Cell Cycle M phase (Mitosis) Interphase G 1 phaseS phaseProphaseG 2 phaseMetaphaseTelophaseAnaphase

Go to Section: Interest Grabber Knowing When to Stop Suppose you had a paper cut on your finger. Although the cut may have bled and stung a little, after a few days, it will have disappeared, and your finger would be as good as new. Section How do you think the body repairs an injury, such as a cut on a finger? 2.How long do you think this repair process continues? 3.What do you think causes the cells to stop the repair process?

Go to Section: Section Outline 10–3Regulating the Cell Cycle A.Controls on Cell Division B.Cell Cycle Regulators 1.Internal Regulators 2.External Regulators C.Uncontrolled Cell Growth Section 10-3

Go to Section: Different types of cells go through the cell cycle at different rates. Contact Inhibition - in normal tissues cells stop dividing when they come into contact with other cells - when contact is lost they begin dividing again - ex.: cut in your skin

Go to Section: Control of Cell Division Section 10-3

Go to Section: Cyclins are chemicals that cells produce which regulate the timing of the cell cycle in eukaryotic cells. A sample of cytoplasm is removed from a cell in mitosis. The sample is injected into a second cell in G 2 of interphase. As a result, the second cell enters mitosis.

Go to Section: Internal regulators – proteins that respond to events inside the cell and allow the cell cycle to proceed or not. - produced only when all DNA is replicated - controls until all chromosomes attached to spindle fibers External regulators – proteins that respond to events outside the cell. - growth factors and surface receptors

Go to Section: Uncontrolled Cell Growth = Cancer - cancer cells do not respond to normal controls - divide uncontrollably and form masses of cells called tumors - cells may metastasize – break loose from tumor and spread - mutations in a gene called p53 are often what triggers cancer

Go to Section: Stem Cells – unspecialized cells which can give rise to other cell types. - in an embryo there are many stem cells which will give rise to the specialized cells of your body - adult stem cells are present, but harder to find - medical research is trying to use stem cells to cure disease.

Go to Section: Figure 10–8 Effect of Cyclins Section 10-3

Video 2 Click the image to play the video segment. Video 2 Animal Cell Cytokinesis

Section 1 Answers Interest Grabber Answers 1.On a sheet of paper, make a drawing of a cell that has the following dimensions: 5 cm x 5 cm x 5 cm. Your partner should draw another cell about one half the size of your cell on a separate sheet of paper. 2.Compare your drawings. How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell? It would take twice the amount of time. 3.What is the advantage of cells being small? If cells are small, materials can be distributed to all parts of the cell quickly.

Section 2 Answers Interest Grabber Answers 1. Why is the cell cycle called a cycle? It represents recurring events. 2. Why do you think that it is important for a cell to grow in size during its cell cycle? If a cell did not grow in size, each cell division would produce progressively smaller cells. 3. What might happen to a cell if all events leading up to cell division took place as they should, but the cell did not divide? Students may infer that a cell that undergoes all sequences of the cell cycle would grow increasingly larger—to a point at which the cell could no longer exchange materials with the environment efficiently enough to live.

Section 3 Answers Interest Grabber Answers 1.How do you think the body repairs an injury, such as a cut on a finger? The cut is repaired by the production of new cells through cell division. 2.How long do you think this repair process continues? Cell division continues until the cut is repaired. 3.What do you think causes the cells to stop the repair process? Students will likely say that when the cut is filled in, there is no room for more cells to grow.

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