Interest Grabber

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Interest Grabber

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 GrowthA. Limits to Cell Growth

1. DNA “Overload”

2. Exchanging Materials

3. Ratio of Surface Area to Volume

4. Cell Division

SURFACE AREA TO VOLUME RATIO LAB

Section 10-1

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10-1 Cell Growth

2 Reasons why cells divide rather than continue to grow indefinitely:

1.The larger a cell becomes, the more demands the cell places on its DNA

2.The cell has more trouble moving enough nutrients and wastes across the cell membrane

Limits to Cell Growth

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10-1 Cell Growth

•DNA store information that controls a cell’s function.

•DNA is found in the nucleus of the cell.

•Food, oxygen, and water must enter a cell through the cell membrane

•Waste must exit a cell through the cell membrane.


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10-1 Cell Growth

•The rate at which things can enter or exit the cell is dependent on a cell’s surface area.•Surface area is the total area of the cell membrane.•The rate at which food and oxygen are used up and waste is produced is dependent on the cell’s volume.•The surface area : volume ratio limits cell growth


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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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10-1 Cell Growth

•Volume increases more rapidly than the surface area. This causes a decrease in the surface area to volume ratio


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10-1 Cell Growth

•Cell division is the process by which a cell divides into two new daughter cells.•Before a cell divides, the cell replicates its DNA. This ensures that each daughter cell will receive a full copy of the DNA.

Division of the Cell

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Interest Grabber

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. 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

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10-2 Cell Division

2 Stages of cell division in eukaryotes:

1.Mitosis

2.Cytokinesis

Mitosis is the division of the nucleus.

Cytokinesis is the division of the cytoplasm.

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10-2 Cell Division

•Chromosomes contain the genetic information that is passed on from one generation of cells to the next.

•Chromosomes are made up of DNA and proteins.

•Human cells have 46 chromosomes.

•Chromosomes are only visible during cell division.

Chromosomes

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10-2 Cell Division

•Before cell division, each chromosomes replicates, creating 2 identical sister chromatids.•Each pair of chromatids is attached at an area called the centromere which is usually located in the center.•When a cell divides, the sister chromatids separate and each new cell receives one of the sister chromatids.

Chromosomes

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10-2 Cell Division

Chromosomes

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10-2 Cell Division

•The cell cycle is the series of events that cells go through as they grow and divide.•During the cell cycle a cell grows, prepares for division, and divides into two daughter cells, each of which then begins the cycle again.

The Cell Cycle

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10-2 Cell Division

The 4 phases of the cell cycle:

1.G1 Phase- Cell Growth

2.S Phase – DNA replication

3.G2 Phase- Preparation for Mitosis

4.M Phase- Mitosis and Cytokinesis

Traditionally, the G1, S and G2 Phases are called interphase.

The Cell Cycle

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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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10-2 Cell Division

G1 Phase

1.Cell increases in size.

2.Synthesis of new proteins and organelles.

Events in the cell cycle

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10-2 Cell Division

S Phase

1.Synthesis of DNA

2.Chromosomes are replicated

3.Key proteins associated with chromosomes are synthesized.


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10-2 Cell Division

G2 Phase

1. Organelles and molecules needed for cell division are produced.


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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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10-2 Cell Division

4 Stages of mitosis:

1.Prophase

2.Metaphase

3.Anaphase

4.Telophase

Mitosis

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10-2 Cell Division

Prophase

1.Chromatin condenses into chromosomes

2.Centrioles separate to the poles

3.Spindle forms from microtubules

4.Nucleolus disappears

5.Nuclear envelope disappears

Mitosis