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 – the larger a cell becomes, the more demands the cell

places on its DNA and the more trouble the cell has moving waste out and nutrients in

1. DNA “Overload” – compare to a library

2. Exchanging Materials – not enough surface area in a large cell for efficient exchange of material

3. Ratio of Surface Area to Volume – divide surface area by volume• Volume increases more rapidly than surface area

4. Cell Division• Solves the problems of the limits to cell growth

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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Section Review 10-1

1. Give two reasons why cells divide.

2. How is a cell’s DNA like the books in a library?

3. What is the solution to the problems caused by cell growth?

4. As a cell increases in size, which increases more rapidly, its surface area or volume?

5. Calculate the surface area, volume, and ratio of surface area to volume of an imaginary cubic cell with a length of 4cm.

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

• Carry genetic information

• Visible when cell is preparing to divide

• Consist of two identical sister chromatids

• Each pair of chromatids is attached to an area called the centromere

B. The Cell Cycle

• Cells grow, prepare for division, and divide into two daughter cells, each cell then goes through the cycle again

Section 10-2

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C. Events of the Cell Cycle

• G1 – 1st growth phase

• S – DNA replication

• G2 – 2nd growth phase and prep for Mitosis

• M – Mitosis and Cytokinesis

• Mitosis is the division of the nucleus

• Cytokinesis is the division of the cytoplasm

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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M phase

G2 phase

S phase

G1 phase

Figure 10–4 The Cell Cycle

Section 10-2

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D. Mitosis – division of the nucleus

1. Prophase – chromatin condenses into chromosomes, centrioles separate, spindle begins to form, nuclear membrane breaks down

2. Metaphase – chromosomes line up along the “equator”, spindle fibers are connected to the centromeres

3. Anaphase – sister chromatids separate into individual chromosomes and are moved apart

4. Telophase – chromosomes gather at opposite “poles” of the cell and lose their distinct shapes, two new nuclear envelopes form

E. Cytokinesis – the division of cytoplasm

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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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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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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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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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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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 Section Review

1. Name the main events of the cell cycle.

2. Describe what happens during each of the four phases of mitosis.

3. Describe what happens during interphase

4. What are chromosomes made of?

5. How do prokaryotic cells divide?

6. How is cytokinesis in plant cells similar to cytokinesis in animal cells? How is it different?

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 CycleA. Controls on Cell Division – when cells come into contact with other

cells, they respond by not growing• Similar process in the human body when repairing flesh from a

cut or bone from a break…cell division takes place rapidly to heal the wound…as the flesh or bone nears repair completion, cell growth slows and controls on cell growth are reinstated

B. Cell Cycle Regulators – Tim Hunt, UK – Mark Kirschner, US• Discoved and named the protein “cyclin”

– Regulates the timing of the cell cycle in eukaryotes

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.

A 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

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Section Outline

1. Internal Regulators • proteins that respond to events inside the cell• Some regulatory proteins make sure a cell does not enter Mitosis

until ALL of the DNA has been replicated• Other regulatory proteins make sure the cell does not enter

anaphase until all chromosomes are attached to the spindle apparatus

2. External Regulators• Proteins that respond to events outside of the cell• Direct cell to speed up or slow down the cell cycle

• Growth factors – embryonic development and wound healing• Surface molecules control excessive cell growth

C. Uncontrolled Cell Growth• Cancer cells do NOT respond to the signals that regulate the

growth of cells• tumors

Section 10-3

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10-3 Section Review

1. What chemicals regulate the cell cycle? How do they work?

2. What happens when cells do not respond to the signals that normally regulate their growth?

3. How do cells respond to contact with other cells?

4. Why can cancer be considered a disease of the cell cycle?

5. Write a hypothesis about what you think would happen if cyclin were injected into a cell that was in mitosis?