viruses and bacteria viruses bacteria viruses, bacteria, and your health table of contents

Viruses and Bacteria

Viruses

Bacteria

Viruses, Bacteria, and Your Health

Table of Contents

Viruses and Bacteria - Viruses

What Is a Virus?

A virus is a tiny nonliving particle that enters and then reproduces inside a living cell. Virus particles are tiny compared to bacteria.


The Structure of VirusesAll viruses have two basic parts: a protein coat that protects the virus and an inner core made of genetic material. Some viruses are surrounded by an outer membrane envelope.

- Viruses


How Viruses MultiplyActive viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells.

- Viruses


Diameter

The diameter of a circle is a line that passes through the center of the circle and has both of its endpoints on the circle. To find the diameter, draw a line like the one shown below. Then use a metric ruler to measure the length of the line. For example, the diameter of a penny is about 1.9 mm.

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DiameterPractice Problem

Measure the diameter

of a quarter.

2.4 cm

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DiameterPractice Problem

Measure the diameter

of a CD.

12 cm

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How Viruses Multiply

Hidden viruses “hide” for a while inside host cells before becoming active.

- Viruses


SequencingAs you read, make two flowcharts that show how active and hidden viruses multiply. Put the steps in the process in separate boxes in the flowchart, in the order in which they occur. How Active Viruses Multiply

Virus attaches to the surface of a living cell.

Virus injects genetic material into cell.

Cell produces viral proteins and genetic material.

Viruses assemble.

Cell bursts, releasing viruses.

- Viruses


SequencingAs you read, make two flowcharts that show how active and hidden viruses multiply. Put the steps in the process in separate boxes in the flowchart, in the order in which they occur. How Hidden Viruses Multiply

Virus attaches to cell.

Virus injects its genetic material.

Cell produces viral proteins and genetic material.

Viruses are assembled.

Cell bursts, releasing viruses.

Virus’s genetic material becomes part of cell’s genetic material.

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End of Section:Viruses


The Bacterial Cell

Bacteria are prokaryotes. The genetic material in the cells is not contained in a nucleus.

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Population Explosion

Suppose a bacterium reproduces by binary fission every 20 minutes. The new cells survive and reproduce at the same rate. This graph shows how the bacterial population would grow from a single bacterium.

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Horizontal axis–time (minutes); vertical axis–number of bacterial cells.

Reading Graphs:

What variable is being plotted on the horizontal axis? What is being plotted on the vertical axis?

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2 cells after 20 minutes;

8 cells after one hour;

64 cells after two hours.

Interpreting Data:

According to the graph, how many cells are there after 20 minutes? One hour? Two hours?

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The number of cells doubles with each division.

Drawing Conclusions:

Describe the pattern you see in the way the bacterial population increases over two hours.

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Not likely. The bacteria will continue to reproduce at this rate only as long as the conditions are favorable.

Predicting:

Do you think the bacterial population will continue to grow at the same rate? Why or why not?

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After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a definition of each Key Term in your own words.

Key Terms: Examples:

- Bacteria

bacteria If Leeuwenhoek had owned one of the high-powered microscopes in use today, he would have seen the single-celled organisms known as bacteria in detail.

cytoplasm The region inside the cell membrane, called the cytoplasm, contains a gel-like material.

ribosome Located in the cytoplasm are tiny structures called ribosomes, chemical factories where proteins are produced.

Key Terms: Examples:flagellum

respiration

binary fission

A bacterial cell may also have a flagellum, a long, whiplike structure that helps a cell to move.

The process of breaking down food to release its energy is called respiration.

Bacteria reproduce by a process called binary fission, in which one cell divides to form two identical cells.

asexual reproduction


sexual reproduction

conjugation

Asexual reproduction is a reproductive process that involves only one parent and produces offspring that are identical to the parent.Sexual reproduction involves two parents who combine their genetic material to produce a new organism, which differs from both parents.During a process called conjugation, one bacterium transfers some of its genetic material to another bacterium through a thin, threadlike bridge that joins the two cells.

endospore


pasteurization

decomposer

An endospore is a small, rounded, thick-walled, resting cell that forms inside a bacterial cell.

During pasteurization, food is heated to a temperature that is high enough to kill most harmful bacteria without changing the taste of the food.

These bacteria, which live in the soil, are decomposers—organisms that break down large chemicals in dead organisms into small chemicals.

Building Vocabulary


More on Bacteria

Click the PHSchool.com button

for an activity about bacteria.

- Bacteria


End of Section:Bacteria

Viruses and Bacteria - Viruses, Bacteria, and Your Health

Common Bacterial Diseases

Many bacterial diseases can be cured with antibiotics.


Common Viral Diseases

Unlike with bacterial diseases, there are currently no medications that can cure viral infections.

- Viruses, Bacteria, and Your Health


Using Prior KnowledgeLook at the section headings and visuals to see what this section is about. Then write what you already know about diseases caused by viruses and bacteria in a graphic organizer like the one below. As you read, write what you learn.

What You Know

What You Learned

1. You can catch a cold from somebody who has one.2. Some diseases can be treated with medicines.

1. You can catch diseases through contact with an infected person, a contaminated object, an infected animal, or an environmental source.

2. Antibiotic resistance results when some bacteria are able to survive in the presence of an antibiotic.



Links on Infectious Diseases

Click the SciLinks button for links on infectious diseases.



End of Section:Viruses, Bacteria, and Your Health


Graphic Organizer

Nonliving Can beuseful

Treated withantibiotics


End of Section:Graphic Organizer

viruses and bacteria viruses bacteria viruses, bacteria, and your health table of contents

Documents

bacteria viruses

active viruses

hidden viruses

structure of viruses

bacteria sequencing

bacterial cell bacteria

bacteria end of section

cells genetic material