Focus on California Life Science 7th Grade Unit 1 - Chapter 3 Cell Structure and Function

Preview , Chapter Cell Structure and Function All living organisms are posed of cells , from just one to many trillions , whose details ly are visible only through a scope . As a basis for understanding this concept a . Students know cells function similarly in all living organisms . Students know the tics that distinguish plant cells from animal cells , including and cell walls . Students know that the us is the repository for genetic information in plant and animal cells . Scientific progress is made by asking meaningful questions and conducting careful investigations . As a basis for understanding this concept and addressing the tent in the other three strands , students should develop their own questions and perform tions . Students will a . Select and use appropriate tools and technology ( including calculators , computers , es , spring scales , microscopes , and binoculars ) to perform tests , collect data , and display data . Construct scale models , maps , and appropriately labeled grams to scientific knowledge ( motion of Earth plates and cell structure ) The cell that has been colored red is lound in blood . This kind ol cell destroys bacteria . 740

i Preview ' emu ! Structure and Function Focus on the BIG Idea What is the structure of a cell ?

Check What You Know You hear that a pinch of soil may contain millions of organisms . What optical tools would you use to see these organisms and to study their structure ?

i as . Chapter 75 The images shown here represent some of the Key Terms in this chapter . You can use this vocabulary skill to help you understand the meaning of some Key Terms in this chapter . Words can sometimes be divided into parts . A root is the part of i the word that carries the basic meaning . A prefix is a word part that is placed in front of the root to change the word meaning . In the word , for example , is the root and is the prefix . The prefix means many . Multicellular means having many cells . The prefixes below will help you understand some Key Terms . Prefix I Meaning I chloroplast A cellular structure that captures energy from sunlight The framework inside a cell many multicellular Having many cells unicellular Having one cell 9580226

' compound mitochondria Chapter Vocabulary Section ( page 30 ) cell tissue cell theory organ unicellular organ system multicellular Section ( page as ) organelle endoplasmic can wan reticulum cell membrane 50 ?

nude chloroplast ( vacuole mitochondria ?

Section ( page 97 ) element compound carbohydrate nucleic acid protein DNA amino acid RNA Section ( page 102 selectively permeable diffusion osmosis passive transport active transport Build Science Vocabulary Online Visit hool . om Web Code Chapter 77 Reading Skill ! Identify Main Ideas The main idea in a section or paragraph is the most . Sometimes the main idea is stated directly . Other times you have to figure it out on your own . Be sure to look at any headings . Headings can help you identify main ideas . The details in a paragraph or section support the main idea . Details are often specific facts and examples . Look for the main idea and details in the paragraph below . What Are Cells ?

Cells are the basic units of structure and function in living things . Cells form the parts of an organism . The structure of a living thing is determined by the variety of ways in which its cells are put together . Cells carry out all the basic functions or of life in an organism , such as getting oxygen and food and getting rid of wastes . Apply It ! Copy the graphic organizer below in your notebook . Complete it by writing the main idea of the paragraph in the box at the top . Then add two important details . Detail Cells form the parts of an organism .

With a Cell in this chapter , you learn that all living things are made of sometimes just one cell , sometimes trillions ! You can study an everyday object that can serve as a model of a cell an uncooked egg . Your Goal To observe how various materials enter or leave the cells of organisms , using an egg as a model of a typical cell To complete this investigation , you will observe what happens when you soak an uncooked egg in vinegar , then in water , food coloring , salt water , and finally in a liquid of your choice measure the circumference of the egg every day , and graph your results explain the changes that you observe in your egg follow the safety guidelines in Appendix A Plan It ! Predict what might happen when you put an uncooked egg in vinegar for two days . How might other liquids affect an egg ?

Find a place where you can leave your egg undisturbed . Then begin your ! 00 00 All living organisms are posed of cells , from just one to many trillions , whose details usually are visible only through a microscope . What are cells ?

How did the invention of the microscope contribute to knowledge about living things ?

What is the cell theory ?

How are the cells of multicellular organisms organized ?

Key Terms cell cell theory unicellular multicellular tissue organ organ system Discovering Cells ( Is Seeing Believing ?

Cut a photograph out of a page in a newspaper . With only your eyes , closely examine the photo . Record your observations . Examine the same photo with a hand lens . Again , record your observations . Place the photo on the stage of a microscope . Use the clips to hold the photo in place . Shine a light down on the photo . Focus the microscope on part of the photo . See Appendix for instructions on using the microscope . Record your observations . Think It Over Observing What did you see in the photo with the hand lens and microscope that you could not see with only your eyes ?

Which tool is a better choice for studying a tiny object ?

A forest is with an amazing variety of living things . Some . are easy to see , but you have to look closely to others . If you look carefully at the of a forest , you can often spots of bright color . A beautiful pink coral fungus grows beneath tall trees . Beside the pink fungus , a tiny red newt perches on a fallen leaf . What do you think a fungus , a tree , and a red newt have in common ?

They are all living things , or organisms . And , like all organisms , they are made of cells . 809 FIGURE Newt and Coral Fungus All living things are made of cells , including this pink fungus and the red newt that perches next to it .

An Overview of Cells Cells are the basic units of structure and function in living things . This means that cells form the parts of an organism and carry out all of an organisms processes . or functions . mu Skin Cells Your skin is made of cells such as these . Applying Concepts What are cells ?

Cells and Structure When you describe the structure of an object , you describe what it is made of and how its parts are put together . The structures of many buildings , for example , are determined by the way in which bricks , steel beams , and other materials are arranged . The structures of living things are determined by the amazing variety of ways in which cells are put together . A red newts cells , for example , form a body with a head and four legs . Cells and Function The functions of an organism include obtaining oxygen , getting rid of wastes , obtaining food , and growing . Cells are involved in all these functions . For example , cells in your digestive system absorb food . The food provides your body with energy and materials needed for growth . Cells function similarly in all organisms . Regardless of the organism they are a part of , cells carry out the basic processes of life in similar ways . Size of Cells Cells are so small that they are measured in units call micrometers ( One micrometer is one millionth of a meter . Each one of your red blood cells is about micrometers across . Figure shows human skin cells . To give you an idea of their size . one square centimeter of your skin surface contains more than cells . No matter how closely you look with your eyes alone , you won ! be able to see the individual cells in your skin . Cells are usually visible only through a microscope . Reading what are some functions that cells ) perform In living things ?

I First Observations of Cells Until the late 16005 , no one knew cells existed because there was no way to see them . Around 1590 , the invention of the microscope enabled people to look at very small objects . The invention of the microscope made it possible for people to discover and learn about cells . As people built more advanced microscopes . it was possible to discover more about cells . Two early contributors to the understanding of cells were Robert and Anton van ( LAY hook ) Both built their own microscopes .

Tech Design Robert One of the first people to observe cells was the English scientist and inventor Robert . built his own compound microscope . which was one of the best microscopes of his time . In 1663 . used his microscope to observe the structure of a thin slice of cork Cork , the bark of the cork oak tree , is made up of cells that are no longer alive . To , the empty spaces in the cork looked like tiny gular rooms . Therefore , called the empty spaces cells . which is a word meaning small described his observations this way These pores , or cells , were not very deep , but consisted of a great many little boxes . What most amazed was how many cells the cork contained . He calculated that in a cubic inch there were about twelve hundred million number he described as The Microscope Improvements Over Time The microscope made the discovery of cells possible . Microscopes have improved in many ways over the last 400 years . 15 First compound 90 ' Simple makers Anton Van ' simple of the microscope one tiny lens , it could la ' magnify 829

Anton van At about the same time that Robert made his discovery , Anton van also began to observe tiny objects with microscopes . was a Dutch businessman who sold cloth . In his spare time , he built simple microscopes . looked at drops of lake water , scrapings from teeth and gums , and water from rain gutters . In many materials , was surprised to find a variety of tiny organisms . noted that many of these tiny organisms moved . Writing in Science Some whirled , some hopped , and some shot through water like . Find , fast . He called these moving organisms ( an ih out more about one the MAL ) animals , microscopes . Then write an which type of or a ?

it that cit ! did make and use ?

I appear In a popular science magazine . Be creative . Emphasize the microscopes usefulness or . describe the wonders that can be seen with it . 1933 A I Go ! i . For Links on cell theory Visit ( Web Code noun Monarch and Milkweed The monarch butterfly caterpillar and the leaf that the caterpillar nibbles on are both made of cells . Applying Concepts Where do the cells of the caterpillar and leaf come from ?

Development of the Cell Theory ! exciting discoveries caught the attention of other researchers . Many other people began to use microscopes to discover what secrets they could learn about cells . and Three German made especially important contributions to knowledge about cells . These scientists were Matthias ( dun ) Theodor , and Rudolf ( FUR ) In 1838 , concluded that all plants are made of cells . He based this conclusion on his own research and on the research of ers before him . The next year , Theodor concluded that all animals are also made up of cells . Thus , stated , all living things are made up of cells . and had made an important discovery about living things . However , they didn explain where cells came from . Until their time , most people thought that living things could come from nonliving matter . In 1855 , proposed that new cells are formed only from cells that already exist . All cells come from cells , wrote . What the Call Theory Says , and others helped develop the cell theory . The cell theory is a widely accepted explanation of the relationship between cells and living things . The cell theory states the following All living things are composed of cells . Cells are the basic units of structure and function in living things . All cells are produced from other cells . The cell theory holds true for all living things . no matter how big or how small . Since cells are common to all living things , they can provide information about the functions that living things perform . Because all cells come from other cells . scientists can study cells to learn about growth and reproduction .

Unicellular and Multicellular Organisms may be composed of only one cell or many trillions of cells . Unicellular , or , organisms include bacteria ( bak ee uh ) the most numerous organisms on Earth . Multicellular isms are composed of many cells . In multicellular organisms , cells are often organized into tissues , organs , and organ systems . A tissue is a group of similar cells that work together to perform a tion . For example , your brain is mostly made up of nervous tissue , which consists of nerve cells . An organ , such as your brain , is made up of different kinds of tissues that work together . In addition to nervous tissue , your brain contains other kinds of tissue that support and protect it . Your brain Unicellular is part of your nervous system , an organ system that directs mu , body activities and processes . An organ system is a group of organs that work together to perform a major function . what is an organ ?

Section Vocabulary Skill Complete the following sentences with Key Terms . Because bacteria each have only one cell , they are organisms . Animals have many cells . Therefore . animals are organism . Reviewing Key Concepts a . Defining structure and function . Explaining Explain this statement Cells are the basic units of structure and function in organisms . Applying Concepts In what important function are the cells in your eyes involved ?

Reviewing What does a microscope enable people to do ?

Summarizing Summarize observations of cork under a microscope . Relating Cause and Effect Why would ' discovery have been impossible without a microscope ?

Assessment Writing in Science Cellular Organization This dog is multicellular . The bacteria that live naturally on its teeth are unicellular . Each green sphere is a bacterial cell . Writing a . Listing What does the cell theory state ?

Explaining What did contribute to the cell theory ?

Applying Concepts Use ideas to explain why plastic plants are not alive . a . Reviewing How do multicellular organisms differ from unicellular organisms ?

Explaining What is the relationship among cells , tissues , and organs ?

Inferring Would a tissue or an organ have more kinds of specialized cells ?

Explain . Chapter as Lab Design and Build a Microscope Problem How can you design and build a compound microscope ?

Design Skills building a prototype , evaluating design constraints Materials book dual magnifying glasses , each with one power and one lens metric ruler cardboard tubes from paper towels , or black construction paper tape Procedure PART Research and Investigate . Work with a partner Using only your eyes , examine words in a book . Then use the power lens to examine the same words . In your notebook , contrast what you saw with and without the magnifying lens . Hold the lens about above the words in the book . When you look at the words through the lens , they will look blurry . Keep the lens about above the words . Hold the lens above the lens , as shown in the photograph on the right . Move the lens up and down until the image is in focus and upside down . Hint You may have to move the power lens up or down slightly too . Once the image is in focus , experiment with raising and lowering both lenses . Your goal is to produce the highest magnification while keeping the image in . When the image is in focus at the position of highest magnification , have your lab partner measure and record the distance between the book and the lens . Your lab partner should also measure and record the distance between the two lenses . Write a description of how the magnified words viewed through two lenses compares with the words seen without magnification .

lens lens black construction paper . Based on what you learned in Part , work with a partner to design your own ( compound ) microscope . Your microscope should consist of one lens and one lens , each attached to a tube of paper or cardboard allow one tube to fit snugly inside the other tube so the distance between the two lenses can be easily adjusted focus to produce a clear , enlarged , down image of the object be made from dual magnifying glasses , cardboard tubes , and tape . Sketch your design on a sheet of paper . Obtain your teacher approval for your design . Then construct your microscope . Evaluate and Redesign 10 . Test your microscope by examining printed words or a printed photograph . Then . ine other objects such as a leaf or your skin . Record your observations . Did your scope meet the criteria listed in Step ?

Examine microscopes made by other dents . Based on your tests and your tion of other microscopes , list ways you could improve your microscope . Analyze and conclude . Observing Compare the images you observed using one lens with the image from two lenses . Evaluating when you used two lenses , how did moving the top lens up and down affect the image ?

What was the effect of moving the bottom lens up and down ?

Building a Prototype Describe how you built your microscope and explain why you built it that way . Evaluating the Impact on Society Describe some of the ways that microscopes have aided scientists in their work . Making Judgments Suppose you had to observe the movement of an ant legs as the ant moved across the ground . You can use a single magnifying glass or the tool you just constructed . which would you select ?

why ?

Communicate imagine it is 1675 . Write an explanation that will convince scientists to use your new scope rather than the variety used by . Describe how your microscope makes the details of organisms more visible .

Students know the that distinguish plant cells from animal cells . including and cell walls . students know that the nucleus is the repository for genetic information in plant and animal cells . What role do the cell wall and cell membrane play in the cell ?

What is the role of the nucleus in the cell ?

What are found in the cytoplasm and what are their functions ?

How do cells differ ?

Key Terms organelle cell wall cell membrane nucleus cytoplasm mitochondria endoplasmic reticulum Golgi body chloroplast I vacuole I lysosome Looking Inside Cells Nasturtiums How Large Are Cells ?

Look at the organism in the photo . The organism is an amoeba ( uh MEE buh ) a large organism . This type of amoeba is about long . Multiply your height in meters by to get your height in millimeters . How many amoebas would you have to stack to equal your height ?

Many of the cells in your body are about one hundredth the size of an amoeba . How many body cells would you have to stack to equal your height ?

Think It Over Look at a metric ruler to see how small is . Now imagine a distance one as long , or . Why ca you see your body cells without a microscope ?

Nasturtiums brighten up many gardens with green leaves and colorful . How do nasturtiums carry out all the tions necessary to stay alive ?

To answer this question , you will take an imaginary journey into the cell of a nasturtium leaf . You will observe some of the structures found in plant cells . You will also learn some differences between plant and animal cells . As you will discover on your journey , there are even smaller structures inside a cell , called . carry out functions within the cell . Iust as your stomach , lungs , and heart have different functions in your body . each organelle has a different function within the cell . Now , hop aboard your ' imaginary ship and sail into a typical plant cell . As you travel through the plant cell , refer to Figure . And be sure to note the differences between plant and animal cells .

la Onion root cells Enter the Cell Your ship doesn have an easy time getting inside the plant cell . It has to pass through the cell wall and the cell membrane . Cell Wall The cell wall is a rigid layer of nonliving material that surrounds the cells of plants and some other organisms . A cell wall helps to protect and support the cell . In plants , the cell wall is made mostly of a strong material called lose . Although the cell wall is tough , many materials , including water and oxygen , can pass through easily . Unlike plant cells , the cells of animals and many celled organisms do not have cell walls . Instead . a protein framework inside the cell called a gives the cells their shape . Cell Membrane After passing through the cell wall , the next barrier you must cross is the . All cells have cell membranes . The cell membrane forms the outside boundary that separates the cell from its environment . In cells with cell walls , the cell membrane is located just inside the cell wall . In other cells . the cell membrane forms the outside boundary that separates the cell from its environment . The cell membrane controls what substances come into and out of a celL Everything the cell needs , from food to gen , enters the cell through the cell membrane . For a cell to survive , the cell membrane must allow these materials to pass in and out , Harmful waste products leave the cell through the cell membrane . The cell membrane also prevents harmful materials from entering the cell . In a sense , the cell membrane is like a window screen . The screen allows air to enter and leave a room , but it keeps insects out . Fortunately , on this trip , your ship can slip ) no animal cells contain cell walls ?

Flaunt cell Wall and Cell Membrane The onion root cells have both a cell wall and a cell membrane . The paramecium has only a cell membrane . but it is dense and tough . Interpreting Photographs What shape do the cell walls give to the onion root cells ?

Cell Structure and Function FIGURE Plant and Animal Cells These show typical structures found in plant and animal cells . Comparing and Contrasting Identify ' one structure found in plant cells but not animal cells . The de of the cell activities , Including reproduction . Endoplasmic Reticulum This network of passageways carries materials from one part of the cell to another . Cell Wall in a plant cell , a stiff wall surrounds the membrane . giving the cell a rigid , boxlike shape . These capture energy on , and The cell membrane protects use it to produce Mos , mature am the cell and regulates what ' the have one large vacuole . EM and theta cytoplasm stores water , food , waste products , and other materials . I

Visit These small structures Web Code function as factories to . Ribosomes cy . gay be to the The cytoplasm Includes mim , um ' Nucleus a fluid in which or they may in The nucleus directs all ' many different he cytoplasm of the cell activities , are including reproduction . Mitochondria Most of the cell energy , is produced within these . A Golgi Body The Golgi bodies receive materials from the endoplasmic reticulum and send them to other parts of the cell . They also release materials outside the cell . These small . Some animal cells have The ' vacuoles that store food the cell and regulates what en pans water , waste , and other substances enter and leave materials . he Ce Go For Plant and Animal Cells activity

FIGURE The Nucleus The photo ( left ) and diagram ( right ) both show the nucleus , which is the cell control center . The chromatin in the nucleus contains instructions for carrying out the activities , Gelatin Cell Make your own model of a cell . Dissolve a packet of colorless gelatin in warm water . Pour the gelatin into a rectangular pan ( for a plant cell ) ora round pan ( for an animal cell ) Choose different materials that resemble each of the cell structures found in the cell you are modeling . Insert these materials into the gelatin before it begins to solidify . Making Models On a sheet of paper . develop a key that identifies each cell structure in your model . Describe the function of each structure . 920 Chromatin Nucleolus Nuclear envelope Sail on to the Nucleus As you sail inside the cell , a large , oval structure comes into view . This structure , called the nucleus ( us ) acts as the control center of the cell . The nucleus is the cell control center , directing all of the cell activities . Nuclear Envelope Notice in Figure that the nucleus is surrounded by a membrane called the nuclear envelope . Just as a mailing envelope protects the letter inside it , the nuclear envelope protects the nucleus . Materials pass in and out of the nucleus through pores in the nuclear envelope . So aim for that pore just ahead and carefully glide into the nucleus . Chromatin You might wonder how the nucleus knows how to direct the cell . The answer lies in those thin strands floating directly ahead in the nucleus . These strands , called chromatin , contain genetic material , the instructions for directing the cell functions . For example , the instructions in the chromatin ensure that leaf cells grow and divide to form more leaf cells . You can think of the nucleus as a repository for genetic mation in cells . A repository is a storage area . Nucleolus As you prepare to leave the nucleus , you spot a small object by . This structure , a nucleolus . is where ribosomes are made . Ribosomes are the where are produced . Proteins are important chemicals in cells . where in the nucleus is genetic material found ?

FIGURE Mitochondrion The mitochondria release most of the cell energy . Inferring In what types of cells would you expect to find a lot of mitochondria ?

in the cytoplasm As you leave the nucleus , you find yourself in the cytoplasm . the region between the cell membrane and the nucleus . Your ship in a clear , thick , The in the plasm is constantly moving , so your ship does not need to pel itself . in the cytoplasm are many , including mitochondria , endoplasmic reticulum , ribosomes , Golgi bodies , vacuoles , and . Each of these has functions in the cell . Mitochondria Suddenly , structures loom ahead . These are mitochondria ( my tuh dree uh ) singular mitochondrion ) Mitochondria are known as the powerhouses of the cell because they convert energy in food molecules to energy the cell can use to carry out its functions . Figure shows a mitochondrion up close . Endoplasmic Reticulum As you sail farther into the plasm , you yourself in a maze of passageways called the endoplasmic reticulum ( en duh mik yuh lum ) The endoplasmic reticulum passageways help form proteins and other materials . They also carry material throughout the cell . Ribosomes Attached to some surfaces of the endoplasmic reticulum are small , bodies called ribosomes . Other ribosomes in the cytoplasm . function as factories to produce proteins . Some newly made proteins are released through the wall of the endoplasmic reticulum . From the interior of the endoplasmic reticulum , the proteins will be transported to the Golgi bodies . Endoplasmic Reticulum The endoplasmic reticulum is similar to the system of hallways in a building . Proteins and other materials move throughout the cell by way of the endoplasmic reticulum . The spots on this organelle are ribosomes , which produce proteins .

ry This Activity Comparing Cells Observe the characteristics of plant and animal cells . Obtain a prepared slide of plant cells from your teacher . Examine these cells under the and power lenses of a microscope . Draw a picture of what you see . Repeat Steps and with a prepared slide of animal cells . Observing How are plant and animal cells alike ?

How are they different ?

940 FIGURE 10 A Golgi Body Golgi bodies are that transport materials . Golgi Bodies As you leave the endoplasmic reticulum , you see the structure shown in Figure 10 . It looks like sacs and tubes . This structure , called a Golgi body , can be thought of as the cell mail room . Golgi bodies receive proteins and other newly formed materials from the endoplasmic lum . They then package and distribute materials to other parts of the cell . Golgi bodies also release materials outside the cell . Have you noticed the many large green in the cytoplasm ?

Only the cells of plants and some other organisms have these green called ( uh ) capture energy from sunlight and use it to produce food . make leaves green . Vacuoles Steer past the and head for that large , sac , called a vacuole ( yoo ohl ) in the cytoplasm . Vacuoles are the storage areas of cells . Most plant cells have one large , central vacuole . Vacuoles store food and other materials needed by the cell . Vacuoles can also store waste products . Animal cells do not have central vacuoles . However , some animal cells have smaller storage . Your journey through the cell is almost over . Before you leave , take another look around you If you carefully swing your ship around the vacuole , you may be lucky enough to see a lysosome . LY suh ) are small , round structures containing chemicals that break down certain rials in the cell . Some chemicals break down large food particles into smaller ones also break down old cell parts and release the substances so they can be used again . In this sense , you can think of as the cell cleanup crew . an What organelle captures the energy of sunlight and uses it to make food for the cell ?

Cell Diversity You just had a tour of a typical leaf cell . But actually , there a lot of variety in within individual organisms and across different organisms . The variety of structure in cells reflects differences in cell function . Cells come in many shapes . Look at the nerve cell and red blood cells in Figure 11 . Notice the long , extensions of the nerve cell . These extensions help transmit information from one part of your body to another . Red blood cells carry oxygen throughout your body . Their shape enables xi them to fit through tiny blood vessels . vessel ' Some cells contain certain but not others . For example , not all plant cells have . Since root cells grow underground away from sunlight , they have no need for . Cells may also have more of a particular kind of organelle . For example , cells that actively produce proteins , such as liver cells , contain many ribosomes . Each human liver cell has millions of ribosomes . Nerve cell FIGURE 11 Specialized Cells Nerve cells carry information throughout the human body . Red blood cells carry oxygen . Developing Hypotheses How do the shapes of these cells help them function ?

Assessment Vocabulary Skill Prefixes The Key Term Identifying Identify the functions of endoplasmic reticulum begins with the prefix , ribosomes and Golgi bodies . which means in 01 ' Within What part . Describing Describe the characteristics of of a cell is the endoplasmic reticulum located ?

the endoplasmic reticulum . Applying Concepts How are the functions ' Key of ribosomes , Golgi bodies , and the a . Comparing and Contrasting Compare the endoplasmic reticulum related ?

functions of the cell wall and the cell a . Listing What are two ways cells can differ ?

membrane in Plan and animal cells . Applying Concepts Which might HOW ( 1065 591101059 With the you expect to see in large quantities in cells Of the Cell Will ?

that actively release proteins outside the cell ?

Identifying What is the key function of the nucleus ?

Writing in Science . Describing Which structure inside the nucleus is involved in this function ?

Predicting Suppose a dye for staining cells stains the region where ribosomes are made . What would you expect to see inside the stained cells nucleus ?

. Sizing Up a Cell Problem How can you build a scale model showing the relative sizes of plant cell ?

Skills Focus calculating , making models Materials various materials provided by your teacher Procedure . The table below gives the approximate sizes of structures in a typical plant cell . Copy the table into your notebook . Convert the size of each structure using the scale one centimeter to one micrometer ( For example , at this scale , a model of a plant cell that is 150 long would be 150 long . I Record your calculations in the third column . Then , calculate the size of each structure at a scale of 10 . Fill in your calculations in the correct column . Now select a scale you would like to use for your model . Calculate the sizes of structures for a cell model built according to the scale you selected . Record your calculations . With your lab partner , choose four cell that would be practical to model . cuss the possible materials you can use . Sketch your design on a sheet of paper . Obtain your teacher approval for your design . Then construct your model . Analyze and Conclude Calculating A plant cell model has been built using the scale one meter to one micrometer . How large would a with a diameter of micrometer be in this model ?

Making Models What scale did you choose to use for your model ?

Why ?

What problems did you encounter in building your model ?

Drawing Conclusions Based on your tions in this lab , why would it be difficult to include all the structures of a cell in a scale model the size of a shoebox ?

I . Communicating You are designing a giant scale model of a cell for a museum exhibit . The museum is able to provide unlimited space and construction materials for your project . Write a memo to your construction team explaining what factors to keep in mind while building a giant cell to scale . 130 ( length ) 80 ( width ) um ( booth ) with )

Section Chemical , in Cells Integrating Standards Focus an Standards Warm Up know CEllS a , function similarly in all living organisms . Your teacher will provide you with containers filled with various What are elements and substances . All of the substances are compounds ?

chemical compounds . How is water important to the . Examine each substance . Read the function of cells ?

label on each container to learn what each substance is made of . Think It Over What are the functions of carbohydrates , proteins . and nude was ?

Forming Operational Definitions Chemical compounds are Key Terms important to the structure and function of all cells . a definition of what you think a chemical compound is . element compound carbohydrate lipid Cells and are very small , but you are surrounded by ' Protein particles even smaller than cells ! Air is made up of trillions of id these tiny particles . They bump into your skin , hide in the ' i add folds of your clothes , and whoosh into your nose every time , DNA your take a breath . In fact , you and the world around you , MA including the cells in your body and all other organisms , are composed of tiny particles . Some of these particles are ments , and others are compounds . One reason why cells tion similarly in all organisms is that cells consists of , use , and produce many identical compounds . Elements and Compounds You may not realize it , but air is a mixture of gases . These gases include both elements and compounds . Three gases in the air are oxygen , nitrogen , and carbon dioxide . Elements Oxygen and nitrogen are examples of elements . An element is any substance that can not be broken down into simpler substances . The smallest unit of an element is called an atom . An element is made up of only one kind of atom . The elements found in living things include carbon , hydrogen , oxygen , nitrogen , phosphorus , and sulfur . 97

( Go 45 For Links on proteins Visit Web Code Home 12 Molecules and Compounds Water is a chemical compound . 50 is carbon dioxide , which is found in the gas bubbles . Applying Concepts What is a compound ?

Water Molecule A water molecule is made up of one atom of oxygen and Compounds Carbon dioxide is a compound made up of the elements carbon and oxygen . When two or more elements combine chemically , they form a compound . Most elements in living things occur in the form of compounds . The smallest unit of many compounds is a molecule . A molecule of carbon dioxide consists of one carbon atom and two oxygen atoms . The Compound Called Water Like carbon dioxide , water is a compound . Each water molecule is made up of two gen atoms and one oxygen atom . Water makes up about two thirds of your body . Water plays many important roles in cells . Water dissolves chemicals that cells need . Most chemical reactions within cells could not take place without water . For example , without water , plants would not be able to convert the energy captured by into food . Water also helps cells keep their size and shape . In fact , a cell without water would be like a balloon without air . addition , because water changes temperature so slowly , it helps keep the temperature of cells from changing rapidly . Inorganic and Organic Compounds Water is an ple of an inorganic compound . An inorganic compound does not contain the element carbon . Sodium chloride , or table salt , is another inorganic compound . Many compounds in living things contain the element bon . Most compounds that contain carbon are called organic compounds . Carbohydrates , lipids , proteins , and nucleic acids are important groups of organic compounds in living things . These organic compounds play important roles in the I function of cells . Oxygen , Carbon Dioxide Molecule The air bubbles contain carbon dioxide . A carbon dioxide molecule has one and two atoms of oxygen .

Carbohydrates A carbohydrate is an organic compound made of the elements carbon , hydrogen , and oxygen . Sugars and starches are examples of carbohydrates . Sugars are produced during the cess that takes place in plants . Foods such as fruits and some vegetables have a high sugar content . Sugar can combine . forming large molecules called starches , or complex carbohydrates . Plant cells store excess energy in molecules of starch . Many foods that come from plants contain starch . These foods include potatoes , pasta , rice , and bread . When you eat these foods , your body breaks down the starch into glucose , a sugar that your cells can use for energy . In addition to providing energy for the cell , carbohydrates are important components of some cell parts . For example , the cellulose found in the cell walls of plants is a type of carbohydrate . are also found in cell membranes . Lipids Have you ever seen a cook trim the fat from a piece of meat before cooking it ?

The cook is trimming away a lipid Fats , oils , and waxes are all lipids . Like carbohydrates . lipids are rich organic compounds made of carbon , hydrogen , and Lipids contain even more energy than carbohydrates . Cells store energy in lipids for later use . For example , during winter , a dormant bear lives on the energy stored in fat within its cells . In addition to their function as an energy source , lipids also make up most of the cell membrane . What are the kinds of lipids ?

FIGURE 14 Lipids Olive oil , which comes from olives such as those shown here , is made mostly of lipids . Making Generalizations What elements are lipids composed of ?

FIGURE 13 Starch These potatoes contain a large amount of starch . Starch is a carbohydrate . The blue grains in the are starch granules in a potato . The grains have been colored blue to make them easier to see . Chapter 99 Reviewing Math Statistics , Data Analysis , and Probability rid Comparing Compounds in Cells ' AI cell Li I Mammal cell Compounds in Bacteria and Mammals Do all cells contain the same amounts of carbohydrates , lipids , proteins , and nucleic acids ?

The graph compares the percentages of different compounds in a bacterial cell and a mammal cell . Reading Graphs What do the red bars represent ?

What do the blue bars represent ?

Interpreting Data Which kind of proteins or nucleic up the larger percentage of a mammal cell ?

Drawing Conclusions In general , how do a Water Proteins Nucleic Lipids Other bacterial cell and a mammal cell compare in their chemical composition ?

TYPO Percent of Total Cell Weight Proteins What do a bird feathers , a spider web , and your have in common ?

All of these substances are made mainly of proteins . Proteins are large organic molecules made of carbon , hydrogen , oxygen , nitrogen . and , in some cases , sulfur . Foods that are high in protein include meat , eggs , nuts , and beans . Structure of Proteins Protein molecules are made up of smaller molecules called amino acids . Although there are only 20 common amino acids , cells can combine them in different . ways to form thousands of different proteins . The kinds of amino acids and the order in which they link together mine the type of protein that forms . You can think of the 20 amino acids as being like the 26 letters of the alphabet . Those 26 letters can form thousands of words . The letters you use and their order determine the words you form . Functions of Proteins Much of the structure of cells is made up of proteins . Proteins form parts of cell membranes . Proteins also make up many of the within the cell . The proteins known as enzymes perform important functions in the chemical reactions that take place in cells . An enzyme is a type of protein that speeds up a chemical tion in a living thing . Without enzymes , many chemical reactions that are necessary for life would either take too long or not occur at all . For example , enzymes in your saliva speed up the digestion of food by breaking down starches into sugars in your mouth . mac

Nucleic Acids Nucleic acids are very long organic molecules made of carbon , oxygen . hydrogen , nitrogen , and phosphorus . acids contain the instructions that cells need to carry out all the functions of life . There are two kinds of nucleic acids . acid ( dee see ry boh noo ik ) or DNA , is the genetic material that carries information about an organism and is passed from parent to offspring . The information in DNA is also used to direct all of the cell functions . Most of the DNA in a cell is found in the chromatin in the nucleus . Ribonucleic acid ( ry boh noo ) or RNA , plays an important role in the production of proteins . RNA is found in the cytoplasm as well as in the nucleus . what are the two kinds of nucleic acids ?

what are their functions ?

FIGURE 15 DNA in the Nucleus A cell nucleus ( colored purple ) contains most of the cell DNA in its Chromatin ( Colored red and yellow ) Assessment Section . Reading Target Reading Skill Identify Main Ideas Reread the text following the heading Structure of Proteins . What sentence expresses the main idea of this paragraph ?

Reviewing Key Concepts A Activity Compounds in Food with family a . Defining What is a compound ?

Classifying What is one inorganic compound vital for chemical reactions in cells ?

What are four groups of organic compounds important to living things ?

Reviewing What three important functions does water perform in cells ?

Relating Cause and Effect Suppose a cell is seriously deprived of water . How might this lack of water affect the cell enzymes ?

Explain . a . Reviewing Which of the four types of organic compounds serve as an energy source for cells ?

Classifying Which of the four types of organic molecules contain the element nitrogen ?

Inferring An organic compound contains only the elements carbon , hydrogen , and oxygen . Could this compound be a carbohydrate ?

Could it be a protein ?

Explain . members , look at the Nutrition Facts labels on a variety of food products . identify foods that contain large amounts of the following organic compounds carbohydrates , proteins , and fats . Discuss with your family what elements make up each of these compounds and what roles they play in cells and in your body . 101

00 Students know cells who I tion similarly in all living organisms . How do most small molecules cross the cell membrane ?

Why is osmosis important to cells ?

What is the difference between passive transport and active transport ?

Key Terms selectively permeable diffusion osmosis passive transport active transport The Cell in Its Environment a ' Standards How Do Molecules Move ?

Stand with your classmates in locations that are evenly spaced throughout the classroom . Your teacher will spray an air freshener into the room . When you first smell the air freshener , raise your hand . Note how long it takes for other students to smell the scent . Think It Over Developing Hypotheses How was each student distance from the teacher related to when he or she smelled the air freshener ?

Develop a hypothesis about why this pattern occurred . As darkness fell , the knight urged his horse toward the castle . The weary knight longed for the safety of the castle , with its thick walls of stone and strong metal gates . The castle keeper opened the gates and slowly lowered the drawbridge . The horse across the bridge . and the knight sighed with relief . Home at last ! Like ancient castles , cells have structures that protect their contents from the world outside . All cells are surrounded by a cell membrane that separates the cell from the outside . The cell membrane is selectively permeable , which means that some substances can pass through the membrane while others can not .

Cells , like castles , must let things enter and leave . All cells must let in needed materials , such as oxygen and food . In contrast , waste materials must move out of cells . Oxygen , food molecules , waste products . and many useful cell products must pass through the cell membrane . Diffusion Substances that can move into and out of a cell do so by one of three methods diffusion , osmosis , or active transport . Diffusion is the main method by which small molecules move across the cell membrane . Diffusion ( is the process by which molecules move from an area of higher concentration to an area of lower concentration . The concentration of a substance is the amount of the substance in a given volume . For example , suppose you dissolve gram of sugar in liter of water . The concentration of the sugar solution is gram per liter . If you did the Standards activity , you observed diffusion in action . The area where the air Freshener was sprayed had many molecules of freshener . The molecules moved from this area of higher concentration to the other parts of the classroom , where there were fewer molecules of thus a lower concentration . What Causes Diffusion ?

Molecules are always moving . As they move , the molecules bump into one another . The more molecules there are in an area , the more collisions there will be . Collisions cause molecules to push away from one another . Over time , the molecules of a substance will continue to spread out . Eventually , they will be spread evenly throughout the area . The concentration of a solution can be expressed as a ratio . A ratio compares two numbers . It tells you how much you have of one item in comparison to another . For example , suppose you dissolve of sugar in of water . You can express the concentration of the solution in ratio form as I This can also be written . Practice Problem Suppose you dissolve of salt in of water . Express the of the solution as a ratio . FIGURE A Selective Barrier The walls of a castle protected the inhabitants within . and the castle gatekeeper allowed only certain people to pass through . Similarly , the cell membrane protects the contents of the cell and helps control the materials that enter and leave . 103

Before Diffusion There is a higher concentration of oxygen molecules outside the cell than inside the cell . Freon 17 Diffusion in Action Molecules move by diffusion from an area of higher concentration to an area of lower concentration . Predicting What would happen if the concentration of oxygen molecules outside the cell was lower than inside the cell ?

Go for More on cellular transport Visit Web Code 1046 After Diffusion The concentration of oxygen molecules is the same outside and inside the cell . Diffusion of Oxygen Have you ever used a microscope to observe organisms in pond water ?

These organisms obtain the oxygen they need to survive from the water around them . Luckily for them , there are many more molecules of gen in the water outside the cell than there are inside the cell . In other words , there is a higher concentration of oxygen molecules in the water than inside the cell . Remember that the cell membrane is permeable to oxygen molecules . The oxygen molecules diffuse from the area of higher pond the cell membrane to the area of lower inside of the cell . By what process do small molecules move into cells ?

Osmosis Like oxygen , water passes easily into and out of cells through the cell membrane . Osmosis is the diffusion of water through a selectively permeable membrane . Because cells can not function properly without adequate water , many cellular processes depend on osmosis . Osmosis and Diffusion Remember that molecules tend to move from an area of higher concentration to an area of lower concentration . In osmosis , water molecules move by diffusion from an area where they are highly concentrated through the cell membrane to an area where they are less concentrated .

Effects of Osmosis Osmosis can have important for the cell . Look at Figure 18 to see the effect of osmosis on cells . In Figure , a red blood cell is bathed in a solution in which the concentration of water is the same as it is inside the cell . This is the normal shape of a red blood cell . Contrast this shape to the cell in Figure . The red blood cell is in water that contains a lot of salt . The of water molecules outside the cell is lower than the concentration of water molecules inside the cell . This ence in concentration occurs because the salt takes up space in the salt water . Therefore , there are fewer water molecules in the salt water outside the cell compared to the water inside the cell . As a result , water moves out of the cell by osmosis . When water A I I A Osmosis in Action . Use water to prepare a slide of ( a freshwater plant ) Observe the leaf cells at low magnification and record your observations . Increase the magnification and record what you see . Place a drop of 10 salt Activity moves out , the cell shrinks . edge of In Figure , the red blood cell is in water that mace a sma ( of contains a very small amount of salt . The water inside the cell on me contains more salt than the solution outside the cell . Thus , the opposite edge of the concentration of water outside the cell is greater than it is inside to draw the salt the cell . The water moves into the cell , causing it to swell . 497 the . in ) How is osmosis related to diffusion ?

Repeat steps and . Inferring What role did osmosis play in the changes mu you observed ?

Effects of Osmosis on Cells In osmosis . water diffuses through a selectively permeable membrane . Water molecules Cell membrane High Water Concentration . Outside Cell . During osmosis , water moves th ell . Concentration of water inside the cell is the same as outside . Low Water Concentration Outside Cell . Water moves out of the cell during osmosis .

Active Transport If you have ever ridden a bicycle down a long hill , you know that it doesn take any of your energy to go fast . But you do have to use some of your energy to pedal back up the hill . For a cell , moving materials through the cell membrane by diffusion and osmosis is like cycling downhill . These processes do not require the cell to use its own energy . The movement of dissolved materials through a cell membrane without using cellular energy is called passive transport What if a cell needs to take ina substance that is present in a higher concentration inside the cell than outside ?

The cell would have to move the molecules in the opposite direction than they naturally move by sion . Cells can do this , but they have to use as you would use energy to . the movement of materials through a cell membrane using cellular energy . Active transport requires the cell to use its own energy , while passive transport does not . Proteins Cells have several ways of moving materials by active transport . In one method , transport proteins in the cell membrane pick up molecules outside the cell and carry them in , using energy . Figure 19 illustrates this process . Transport proteins also carry molecules out of cells in a similar way . Some substances that are ried into and out of cells in this way include calcium , potassium , and sodium . A cell membrane may contain many transport proteins . Each transport protein can carry a substance . Four 19 Passive and Active Transport Passive and active transport are two processes by which materials pass through the cell membrane . Interpreting Diagrams What is the function of a transport protein ?

Transport by Engulfing Figure 20 shows another method of active transport . First , the cell membrane surrounds and engulfs , or encloses , a particle . Once the particle is engulfed , the cell membrane wraps around the , cle and forms a vacuole within the cell . The cell must use energy in this process . Why Cells Are Small As you know , most cells are so small that you can not see them without a scope . Have you ever wondered why cells are so small ?

One , reason is related to how materials move into and out of cells . mo 20 As a size increases , more of its cytoplasm is located Food ther from the cell membrane . Once a molecule enters a cell , it is This amoeba is carried to its destination by a stream of moving cytoplasm , Th I If it what like the way currents in the ocean move a raft . But in a very large cell , the streams of cytoplasm must travel farther to bring Engulfing is a form of active materials to all parts of the cell . It would take much longer for a . molecule to reach the center of a very large cell than it would in a small cell . Likewise . it would take a long time for wastes to be removed . If a cell grew too large , it could not function well enough to survive . what prevents cells from growing very large ?

Section Assessment Target Reading Skill Identify Main Ideas , Comparing and Contrasting How is active Reread the text following the heading Osmosis . transport different from passive transport ?

What is the main idea of the text under this Reviewing what are transport proteins ?

Explaining Explain why transport proteins Reviewing Key Concepts ' to function in active a . Defining What is diffusion ?

Relating Cause and Effect Use diffusion to explain what happens when you drop a sugar cube into a mug of hot tea . a . Defining What is osmosis ?

Describe at ?

A scientist dissolves 60 of sugar in of move through the cell membrane during is ' BA I , I . hee concentration of the solution in grams concentration of water molecules in Solution Per me is higher than that in Solution A . Describe . Ratios Express the concentration as a ratio . how the water molecules will move . 101

Chapter Study Guide ' Cells are the basic building blocks of all living things . All cells I I a . have similar structures and carry out similar functions . Discovering Cells ' Key Concepts Cells are the basic units of structure and function in living things . The invention of the microscope enabled people to discover and learn about cells . The cell theory states the following All living things are composed of cells . Cells are the basic units of structure and function in living things . All cells are produced from other cells . In multicellular organisms . cells are often organized into tissues , organs , and organ systems . Key Terms cell tissue cell theory organ unicellular organ system multicellular Looking Inside Cells Key Concepts . A cell wall helps to protect and support a plant cell . The cell membrane controls what substances come into and out of a cell . The nucleus directs the cells activities . In the cytoplasm are many , including mitochondria , endoplasmic reticulum . ribosomes , Golgi bodies . vacuoles . and . Each of these has functions in the cell . The variety among cells reflects in structure and function . Key Terms endoplasmic organelle reticulum cell wall Golgi body cell membrane chloroplast nucleus vacuole cytoplasm lysosome mitochondria Chemical Compounds in Cells Key Concepts An element is any substance that can not be broken down into simpler substances . When two or more elements combine chemically . they form a compound . Most chemical reactions within cells could not take place without water . Carbohydrates , lipids , proteins , and nucleic acids are important groups of organic compounds in living things . Carbohydrates provide energy for the cell and are important components of some cell parts . Lipids function as an energy source and make up most of the cell membrane . The proteins known as enzymes perform important functions in the chemical reactions that take place in cells . Nucleic acids contain the instructions that cells need to carry out all the functions of life . Key Terms element enzyme compound lipid carbohydrate nucleic acid protein DNA amino acid RNA The Cell in Its Environment Key Concepts Diffusion is the main method by which small molecules move across the cell membrane . Osmosis is important because cells can not function properly without adequate water . Active transport requires the cell to use energy , while passive transport does not . Key Terms selectively permeable passive transport diffusion active transport osmosis

Review and Assessment . For Visit Web ( ode Target Reading Skill ' Identifying Main Ideas To review part of 09 ! 00 ! Section , reread the text following the heading The Called Water . Copy the Dem om om graphic organizer at right . Complete the , graphic organizer by supplying details that a . support the main idea . Reviewing Key Terms Choose the letter of the best answer . Complete the following sentences so that All mugs are composed of your answers clearly explain the Key Terms . The nucleus can direct the cell activities . because it contains vacuoles . cells . plant and animal cells , the control center of the cell is the chloroplast . Saliva in your mouth is an example of an nude enzyme because . Golgi body . 10 . Oxygen molecules enter a cell by diffusion . A storage compartment of the cell is the cell wall . I ) lysosome . endoplasmic reticulum . vacuole . Mitochondria are powerhouses of the cell because . Water is an example of a compound . which is . Starch is an example of a . nucleic acid . protein . lipid . i i . carbohydrate . in . The process by which water moves across a cell membrane is called . osmosis . SCION active transport . organelle . resolution . Cell Structure and Function Chapter ! 109

Review and Assessment Checking Concepts 11 . What role did the microscope play in the development of the cell theory ?

12 . Describe the function of the cell wall . 13 . Explain the difference between elements and compounds . 14 . How are enzymes important to living things ?

15 . What are the functions of DNA and RNA ?

16 . Why is water important in the cell ?

17 . What is diffusion ?

What function does diffusion have in the cell ?

18 . Explain the relationship between cell size and the movement of materials into and out of cells . Thinking Critically 19 . Applying Concepts Do the cells below come from a plant or an animal ?

Explain your answer . 20 . Problem Solving A cell is actively producing a protein to be released outside the cell . Sequence the following in the order that the protein will travel Golgi bodies , ribosomes , endoplasmic reticulum . 21 . Predicting Suppose a cell did not have a supply of amino acids and could not produce them . What effect might this have on the cell ?

22 . Comparing and Contrasting Explain how active transport is different from osmosis . Math Practice 23 . Ratios A solution consists of 24 of table salt dissolved in of water . Express the concentration of salt in the form of a ratio . 24 . Ratios What is the concentration of a sugar solution that contains sugar dissolved in 500 of water ?

Express your answer in the form of a ratio . Applying Skills Use the diagrams to answer Questions . A scientist watered the plant in Figure A with salt water . After 30 minutes , the plant looked as you see it in Figure . 25 . Observing How did the plant cells change after the plant was watered ?

25 , Inferring Describe a process that would lead to the changes in the plant cells . 27 . Developing Hypotheses Suppose the scientist were to water the plant in with fresh ( unsalted ) water . Develop a hypothesis about what would happen to the plant . Explain your hypothesis . Standards Investigation Performance Assessment Bring in your eggs graph , and any diagrams you made . As a class , discuss your results and conclusions . Then , in a group , try to answer these questions What happened to the eggshell ?

What process took place at each stage of the experiment ?

Standards Practice Choose the letter of the best answer . A reasonable estimate for the size of a cell nucleus is A . Which of the following statements is not true according to the cell theory ?

A All plants and animals are made of cells . Cells are the basic unit of structure in organisms . Only some cells come from other cells . All cells come from other cells . Use the table below and your knowledge of science to answer Question . Comparing the Cells of Three Organisms . Which organism is most likely an animal ?

A Organism I Organism Organism None of the organisms is an animal . Which of the following statements about a cell membrane is true ?

A Only small molecules can pass through the membrane . Only water molecules can pass through the membrane . Only food molecules can pass through the membrane . Some substances can pass through the membrane while others can not . Success Tracker at A tissue in an animal produces and releases chemicals that are used by cells throughout the animal body . Cells in that tissue probably have a larger than normal number of A . mitochondria . Golgi bodies . nuclei . Use the diagram below and your knowledge of science to answer Questions and . A . Which organelle contains instructions for directing the cell functions ?

A A . In which organelle is food energy converted to energy that the cell can use ?

AA . How are plant and animal cells similar ?

How are they different ?

Make a list of the different in each cell . Explain how each organelle is vital to the life and function of a plant or animal . 111