Introduction

Chapter 9. Nutrition, Metabolism, Enzymes

Interactive Study Guide
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Welcome to the Interactive Study Guide for Chapter 9: Cell Division and Mitosis! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Nature’s Pharmacy:

From the bark of an ancient evergreen tree, a cancer treatment blockbuster

DRIVING QUESTIONS

  • When and how does normal cell division occur in the body?
  • How do normal cells and cancer cells differ with respect to cell division?
  • How are cancer treatment decisions made for a given patient?
  • How are new cancer drugs developed?

Driving Question 1

When and how does normal cell division occur in the body?

Why should you care?

Cell division makes new cells from older ones. This is the process by which multicellular organisms—such as humans—grow, repair, and maintain their bodies. Understanding the purposes of cell division will help you understand how your body works, and some ways it may malfunction.

The cell cycle is the name for the different steps that a cell progresses through during the course of its normal functioning and division. Understanding the cell cycle is essential for understanding the processes involved in cell division and the diseases associated with their control mechanisms.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain how cell division enables multicellular organisms to grow and develop, maintain themselves, and repair injuries.
  2. Define and diagram the cell cycle, including its major phases.
  3. Explain the importance of the phases of the cell cycle.

Infographic Focus

The infographics most pertinent to the Driving Question are 9.1, 9.2, and Up Close: Cell Cycle and Mitosis.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The segregation and separation of duplicated chromosomes during cell division.
The specialized region of a chromosome where the sister chromatids are joined; critical for proper alignment and separation of sister chromatids during mitosis.
The ordered sequence of stages that a cell progresses through in order to divide during its life; stages include preparatory phases (G1, S, G2) and division phases (mitosis and cytokinesis).
Protein at the centromere that provides an attachment point for microtubules of the mitotic spindle.
The physical division of a cell into two daughter cells.
The process by which a cell reproduces itself; cell division is important for normal growth, development, and repair of an organism.
Hollow protein fibers that are key components of the cytoskeleton and make up the fibers of the mitotic spindle.
The stage of the cell cycle in which cells spend most of their time, preparing for cell division. There are three distinct subphases: G1, S, and G2.
The structure that separates sister chromatids during mitosis.
The two identical DNA molecules that make up a duplicated chromosome following DNA replication.
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Explain how cell division enables organisms to grow, maintain themselves, and repair injuries.

1.

What are three reasons for cell division?
Three reasons for cell division are embryonic development, cell replacement, and wound healing.

Define and diagram the cell cycle, including its major phases.

4.

What happens during the cell cycle?
The cell cycle is a series of steps that a cell goes through to divide and become two cells. The steps include preparatory phases (G1, S, G2) and division phases (mitosis and cytokinesis).

Explain the importance of the phases of the cell cycle.

6.

Fill in the following table:

Phase of the Cell Cycle Major Events How is it different from the preceding phase? How is it different from the phase that follows?
Interphase G1

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Interphase S

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Interphase G2

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Prophase

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Metaphase

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Anaphase

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Telophase

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Cytokinesis

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Review Questions

7.

What is the longest phase of the cell cycle?

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Driving Question 2

How do normal cells and cancer cells differ with respect to cell division?

Why should you care?

Cell division in humans and other multicellular organisms is highly regulated. Errors in cell division during early development can lead to deformities and disorders, including cancer.

Cancer is one of the most dreaded diseases. It is the result of unregulated cell division, which can result in a mass of abnormal cells called a tumor.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Predict events that may halt the cell cycle in damaged cells and lead to apoptosis.
  2. Differentiate between normal cell division and the unregulated cell division that leads to cancer.

Infographic Focus

The infographics most pertinent to the Driving Question are 9.2 to 9.5 and Up Close: Cell Cycle and Mitosis.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
A cellular mechanism ensuring that each stage of the cell cycle is completed accurately.
A change in the nucleotide sequence of DNA.
A mass of cells resulting from uncontrolled cell division.
Programmed cell death; often referred to as cellular suicide.
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Predict events that may halt the cell cycle and lead to apoptosis.

9.

What problems can stimulate the cell cycle checkpoints to stop the cell cycle and lead to programmed cell death, apoptosis?
Some problems that can stop the cell cycle and lead to programmed cell death (apoptosis) are mutations in the DNA, an incomplete phase or irreparable damage.

Differentiate between normal cell division and the unregulated cell division that leads to cancer.

10.

What’s the difference between healthy cells and cancer cells? Refer to Infographic 9.5 in your textbook if necessary.
Healthy cells divide when they receive a signal to do so. As they work their way through the cell cycle, various checkpoints assess different aspects of the progress of the cell, such as the completion of the previous step or detection of any mutations in the DNA. In a healthy cell, if mutation or irreparable damage is found, the cell undergoes apoptosis. In contrast, a cancer cell typically does not need a signal to divide, so it does so at inappropriate times and to an inappropriate degree. Cancer cells are also not stopped at checkpoints if there is a problem with the DNA or cell itself. They are allowed to continue through the cell cycle to make more copies of the mutated cancerous cell. This cycle goes on indefinitely.

Review Questions

11.

A cell that has finished the cell cycle with double the normal number of chromosomes would likely be produced if ____________ happened without ____________ during the cell cycle.

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Driving Question 3

How are cancer treatment decisions made for a given patient?

Why should you care?

Few people are fortunate enough not to have cancer affect their own life or the lives of those they care about. The terminology pertaining to cancer and treatments used for cancer are numerous and can be confusing. Understanding how cancer results from mistakes in the mechanisms that control the cell cycle provides a useful perspective on modern cancer treatments and can make this disease a little less baffling.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain how chemotherapy and radiation therapy are related to the cell cycle and how each is used to treat different types of cancer.
  2. Explain how the side effects of chemotherapy and radiation therapy are related to the cell cycle.

Infographic Focus

The infographics most pertinent to the Driving Question are 9.6 and 9.7.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The spread of cancer cells from one location in the body to another.
The use of ionizing (high-energy) radiation to treat cancer.
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Explain how chemotherapy and radiation therapy are related to the cell cycle.

13.

Chemotherapy and radiation therapy both interfere with cell division. Why is that important when treating cancer?
The hallmark of cancer cells is uncontrollable cell growth and division. So a good method to stop cancer cells is to stop cell division.

Explain how the side effects of chemotherapy and radiation therapy are related to the cell cycle.

18.

Consider the case of a person with intestinal cancer who first receives chemotherapy and then, after a rest from the therapy, receives radiation therapy. How are the side effects of the two therapies alike, and how do they differ?

The side effects of the two treatments are alike in that they both target rapidly dividing cells, in this case the intestinal lining, and thus the patient probably becomes nauseous and vomits frequently. The two treatments differ in that the side effects of chemotherapy affect the entire body, since the drug is systemic, while radiation therapy’s side effects are limited to the main target region (the intestinal lining). With chemotherapy, the patient probably loses the hair and becomes more susceptible to infection, since the treatment also targets hair follicles and bone marrow cells.

Thought Question: Why is it so difficult to target only cancerous cells for destruction?

Review Questions

19.

If you were an oncologist and saw a patient with a tumor in the breast, what would be your first recommendation for treatment?

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Driving Question 4

How are new cancer drugs developed?

Why should you care?

With the prevalence of cancer and the often unpleasant side effects of conventional treatment, alternative treatments are constantly being pursued. Cancer will eventually acquire resistance to conventional therapies and treatments; this is why the drive to discover and develop new therapies is extremely important for the future well-being of millions of patients.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Describe how Taxol, a chemotherapy drug, was discovered.
  2. Predict the kinds of animal or plant products that may prove to be effective cancer treatments.

Infographic Focus

The infographics most pertinent to the Driving Question are 9.4 to 9.6.

Describe how Taxol, a chemotherapy drug, was discovered.

21.

How was Taxol, a natural product, discovered?
Taxol was discovered during a plant survey program sponsored by the National Cancer Institute. Scientists were looking for naturally occurring anticancer drugs that could be isolated from the environment. Arthur Barclay is credited with harvesting the bark of the Pacific Yew tree that Taxol was eventually isolated from.

What kinds of animal or plant products may prove to be effective cancer treatments?

22.

What would make a good anticancer agent? Where might some of these agents exist in nature?
Theoretically a good anticancer agent would be some protein, antibody, or molecule that targets only cancer cells and causes their destruction through apoptosis or other mechanisms. Other good anticancer agents may target rapidly dividing cells, as the current therapies do.

There are many possible answers to the second question. In fact, this question is on the minds of many prominent research scientists and medical professionals. Thus far, the anticancer agents that have been explored for human use have come from plants and exist as toxins to prevent that plant from being eaten. This doesn’t mean, however, that all the anticancer agents will come from plants or even be toxic defense mechanisms. It is possible that other naturally occurring proteins, such as those that help in the regeneration of starfish, for example, could provide important clues as to what kind of agent will stop the division of cancer cells. Antibodies are another potential source of anticancer therapeutics. It is possible that an antibody recognizing a breast cancer cell might be found in a mammal such as a platypus. It may seem outlandish, but I assure you, weirder things have happened in the world of science.

Review Questions

23.

True or False. A good anticancer drug would target any cell that had a mutation in its DNA.

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B.
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Thought question: With government funding being cut in almost all areas of research, including cancer, what do you think that means for new anti-cancer drug discovery?

Try again.

Incorrect.

Thought question: With government funding being cut in almost all areas of research, including cancer, what do you think that means for new anti-cancer drug discovery?

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