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.

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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 10-1

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 taketo 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?

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Section Outline

10–1 Cell 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

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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

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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

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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

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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

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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 10-2

1. 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?

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Section Outline

10–2 Cell DivisionA. ChromosomesB. The Cell CycleC. Events of the Cell CycleD. Mitosis

1.Prophase2.Metaphase3.Anaphase4.Telophase

E. Cytokinesis

Section 10-2

Video 1

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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

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Cell Cycle-1. Cell grows2. Prepares for division3. Divides to form 2 daughter cells4. Daughter cells begin cycle again

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M phase

G2 phase

S phase

G1 phase

Figure 10–4 The Cell Cycle

Section 10-2

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InterphaseThis phase consists of:

G1 phase-main growth of a cellS phase- DNA replicated

G2 phase-many organelles and molecules required for celldivision are produced

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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Mitosispart of eukaryotic cell division in which the nucleus divides

Lasts a few minutes to several days.Four phases:

1. Prophase 2. Metaphase3. Anaphase4. Telophase

Section 10-2

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ProphaseThis is the first and longest phase.Events that take place include:

1. chromosomes become visible2. centrioles separate and move to opposite

sides3. spindle (fan-like microtubule structure) forms4. chromosomes attach to spindle fibers

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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MetaphaseSecond phase of mitosisEvents that take place include:1. chromosomes line up in the center of the cell2. microtubules connect the centromere of each chromosome to the two poles of the spindle

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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AnaphaseThird phase of mitosisEvents 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

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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TelophaseFourth and final phase of mitosisEvents 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

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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CytokinesisAnimal 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

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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includes

is divided into is divided into

Concept Map

Section 10-2

Cell Cycle

M phase (Mitosis)

Interphase

G1 phase S phase ProphaseG2 phase Metaphase TelophaseAnaphase

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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 10-3

1. 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?

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Section Outline

10–3 Regulating 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

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Control of Cell Division

Section 10-3

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A sample of cytoplasm is removed from a cell in mitosis.

The sample is injected into a second cell in G2

of interphase.

As a result, the second cell enters mitosis.

Figure 10–8 Effect of Cyclins

Section 10-3

Click the image to play the video segment.

Video 2

Animal Cell Cytokinesis

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 taketo 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.

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.

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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