Overview Cells. Meeting Individual Needs. Directed Reading for Content Mastery

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1 Directed Reading for Content Mastery Overview Cells Directions: Complete the concept map using the terms listed below. lysosome chloroplast mitochondria cell wall 1. An animal cell ribosome Aplant cell nucleus Directions: Complete the following sentences using the terms listed below. virus cytoplasm microscope vaccine cell theory 5. A is often used to prevent viral diseases. 6. We need to use a to see most cells. 7. Cells are filled with a gelatinlike mixture called. 8. A is a disease-causing strand of hereditary material surrounded by a protein coating The was developed from the observations and conclusions of several scientists. Cells 19

2 Directed Reading for Content Mastery Key Terms Cells Directions: Write the letters of the correct terms in the space beside each definition. 1. It is a structure made up of different types of tissues that work together. 2. They are green organelles in the cytoplasm of plant cells. 3. This is a gelatinlike material inside every cell. 4. This is the outer covering that protects all cells. 5. It directs all the activities of cells. 6. It releases energy in food that cells need. 7. It is a summary of scientific observations and conclusions about cells. 8. It protects the cells of plants, algae, fungi, and most bacteria. 9. It is a strand of hereditary material surrounded by a protein coating. 10. It is a group of similar cells that work together to do one job. 11. This kind of cell is a membranebound structure. 12. This kind of cell no internal membranebound structure. a. cell membrane b. cytoplasm c. prokaryotic d. cell theory e. mitochondrion f. tissue g. cell wall h. chloroplasts i. eukaryotic j. organ k. virus l. nucleus 22 Cells

3 Directed Reading for Content Mastery Section 1 Cell Structure Section 2 Viewing Cells Directions: Write T if the statement is true; write F if the statement is false. 1. Fungi have prokaryotic cells. 2. Most one-celled organisms are prokaryotic. 3. Plants and animals have eukaryotic cells. 4. Animal cells are enclosed in a cell wall. 5. The cell membrane is the protective layer around all cells. Directions: Study the following diagram. Then use it to answer the questions on the lines provided. Specimen Appearance of specimen Magnified object Light source Light rays Objective lens Light ray Eyepiece lens 6. a. A microscope contains one or more glass lenses. What do the lenses do to light that passes through them? b. How does this affect the way an object appears when it reaches your eye? 7. The microscope s objective lens a magnification of 40. How many times will it magnify the specimen? 8. A microscope s objective lens magnifies an object 40 times. The eyepiece magnifies an additional 10 times. What is the microscope s total magnification? 20 Cells

4 1 Reinforcement Cell Structure Directions: Complete the following table using the correct cell part or function. Cell part 1. Function gelatinlike mixture that flows inside the cell membrane cell membrane endoplasmic reticulum chloroplast cell wall Golgi bodies directs all cell activities 4. makes protein releases energy stored in food stores water, waste products, food, and other cellular materials 10. breaks down food molecules, cell wastes, and worn-out cell parts Directions: Study the following diagrams. Then identify each part by filling in the blanks in the center. Animal cell Plant cell Cells 27

5 1 Enrichment The Early Cell Explorers It s hard to believe, but there was a time when we didn t know anything about cell structure. In fact, the word cell (from the Latin word for chamber, cello) wasn t used as a biological term until That s when Robert Hooke, an English-born scientist, looked at a thin slice of a cork plant under a compound microscope he had built himself. Hooke noticed small holes surrounded by walls and named these tiny pores cells. After that, scientists believed cells were found only in plants. But in 1839, Matthias Schleiden and Theodor Schwann, both German scientists, shared their scientific findings with one another. Schleiden had been studying plant cells and Schwann had been studying animal structures. Together, they compared plant and animal structures and found that the structures were very similar too similar to be accidental. They concluded that cells are the basic building blocks for both plants and animals. In 1858, Rudolf Virchow took Schleiden s and Schwann s theory and stated it simply: all cells come from other cells. This remains known as the cell theory. Throughout the mid-1800s and into the 1900s, scientists continued to discover more and more about cells thanks in part to Gregor Mendel s study of genetics, Friedrich Miescher s discovery of nuclein (which later became known as DNA), and James Watson s findings about DNA s structure. Although many amazing discoveries have happened in recent years, including genetic engineering and gene therapy, all of it is because of the work of those early cell explorers. 1. How important was Hooke s homemade microscope to the discovery of the plant cell? Explain. 2. Restate the cell theory in your own words. 3. Why do you think it took almost 200 years for scientists to formulate the cell theory? 30 Cells

6 2 Reinforcement Viewing Cells Directions: In numbers 1 4 below, a code letter been substituted for each letter of the alphabet. To find out what the sentence says, use the following key to decode. it. In the key, the code letters are shown directly below the alphabet letter each stands for. Write the correct letter above each code letter, then read the sentence aloud. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Z Y X W V U T S R Q P O N M L K J I H G F E D C B A 1. ZOO LITZMRHNH ZIV NZWV LU XVOOH 2. Z XVO O R H G S V Y Z H R X F M RG LU H G I F XG F I V ZMW UFMXGRLM RM ZM LITZMRHN 3. VEVIB XVOO XLNVH UILN ZMLGSVI XVOO 4. GSRH RH XZOOVW GSV XVOO GSVLIB Directions: Answer the following questions on the lines provided. 5. Who was the first person to look at cells with a microscope? 6. In what material did he see cells? 7. What did Schleiden and Schwann conclude about cells? 8. What instrument uses light and one or more lenses to view cells? 9. What instrument uses a magnetic field to magnify images up to 1,000,000 times? 28 Cells

7 2 Enrichment Using the Microscope There are many different kinds of microscopes. A magnifying glass is a simple microscope. The term microscope commonly refers to a compound light microscope. These microscopes are called compound because they are made of two sets of glass lenses in a tube or tubes. The total magnifying power of a compound light microscope is the product of the magnifying power of the lens in the eyepiece and the magnifying power of the lens in the objective. Most compound light microscopes can magnify a specimen up to 1,000 times its real size. Directions: Using the information above, complete the table by filling in the blanks. Microscopes allow you to see fine details. Spaces between objects that are closer together than 0.1 mm can be seen. The ability of a microscope to separate very small distances is called resolving power. If the resolving power of the lens is not good, the image will appear blurred. When you look into the eyepiece of a microscope, the circular area you see is the field of view. When a ruler is placed across the opening on the stage, the field of view can be measured in millimeters. Eyepiece lens Objective lens Total Microscope 1 10x Low 5x High 40x Low 1. High 400x Microscope 2 8x 10x 60x Microscope x 5. 50x 300x Directions: Answer the following questions on the lines provided. 6. How do you find the total magnifying power of a microscope? 7. What would cause an image to appear blurred? Figure cm 8. What is the width of the field of view shown above? In centimeters? In millimeters? Cells 31

8 Directed Reading for Content Mastery Section 3 Viruses Directions: Study the diagram showing the reproduction cycle of viruses. Then write a sentence describing each stage. Virus Host cell 4. Nucleus 2. Viral hereditary material Viral proteins Cells 21

9 3 Reinforcement Viruses 1. Listed below are the steps by which an active virus copies itself and destroys a cell. Number the steps in the correct order in the blanks provided at the left. a. The cell bursts open and hundreds of new virus particles are released. These new virus particles go on to infect other cells. b. A specific virus attaches to the surface of a specific host cell. c. The viral hereditary material takes control of the host cell and the cell begins to make new virus particles. d. The hereditary material of the virus entering the host cell. Directions: Answer the following questions using complete sentences. 2. Explain what a latent virus does when it enters a cell. 3. Discuss several ways to prevent viral infections. 4. What are vaccines made from? 5. How does gene therapy work? Cells 29

10 3 Enrichment The Size of Viruses Directions: Study the following diagram. It shows the sizes of viruses, bacteria, and blood cells. The largest is a red blood cell. Then answer the questions that follow. Cells Largest diameter in (micrometers) Red blood cells Bacteria Streptococcus Herpes simplex virus Rabies virus 125 Flu virus 85 Polio virus 27 Virus that affects plants 15 Red blood cell molecule How large is the smallest virus on the diagram that affects plants? 2. What is the smallest thing shown on the diagram? 3. The smallest virus on the diagram attacks what kinds of organisms? 4. How do the rabies virus and the polio virus compare in size? 5. How large is the Streptococcus bacteria? Red blood cell molecules? 6. Generalizing from this diagram, infer which are larger, viruses or bacteria 32 Cells