Reading Essentials for Biology Glencoe (794133), страница 20
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Choose one of the following headings in the Read to Learn section: Maintaining a Balanceor Structure of a Plasma Membrane.Turn the heading into a question. Write the question in the space below. Then write youranswer to that question on the lines that follow.Question:Answer:Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Visit the Glencoe Science Web site at science.glencoe.comto find your book and learn more about the plasma membrane.READING ESSENTIALSChapter 773NameDateClassSection7.3 Eukaryotic Cell StructureSC.F.1.4.3 The student knows that membranes are sites for chemical synthesis and essential energy conversions.
Alsocovers SC.B.1.4.1, SC.B.1.4.2, SC.F.2.4.2◗ Before You ReadIn this section you will learn about the various parts of eukaryotic cells. For cells to function correctly, each part does its job. Think of a group that you belong to. On the lines below, list the members of the group. Consider how well the group functions when all members work together.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCellular Boundaries1. Which organelle in thenucleus makes ribosomes?________________________________________________________________________74Chapter 7The Nucleus and Cell ControlThe nucleus directs the activity of a cell’s organelles.
It alsocontains directions to make proteins. Strands of DNA calledchromatin are located within the nucleus. The chromatin tellsthe cell what kinds of proteins to make. When a cell divides, thechromatin condenses and becomes chromosomes.How do ribosomes make protein?The nucleolus inside the nucleus is an important organelle.It makes ribosomes.
Ribosomes are where the cell makes proteinaccording to the DNA directions. Ribosomes are not bound by amembrane. They are made up of RNA and protein.To make protein, ribosomes move out of the nucleus and intoa thick fluid in the cell called cytoplasm. The nuclear envelopeis the boundary between the nucleus and the cytoplasm.
It is amembrane of two phospholipid bilayers. Ribosomes and copiesof the DNA pass through this nuclear envelope on the way tothe cytoplasm.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Restate theMain Point Highlight themain idea in each paragraph.As you read this section, stopafter every few paragraphsand put what you have justread into your own words.As you have already learned, the plasma membrane acts as theflexible boundary of the cell. In plant cells, fungi, bacteria, andsome protists, there is an additional boundary—the cell wall.The cell wall is a rigid wall outside the plasma membrane.
Itgives extra support and protection to the cell.NameDateClassSection7.3Eukaryotic Cell Structure, continuedAssembly, Transport,and StorageA eukaryotic cell contains theendoplasmic reticulum (ER). TheER is a series of tightly folded membranes floating in the cytoplasm.The Eukaryotic CellRough endoplasmicreticulumSmoothendoplasmicreticulumGolgiapparatusCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is the purpose ofthe ER?The endoplasmic reticulum isLysosomethe site of cellular chemical reactions.
There are two types of ER.NucleolusThe areas where ribosomes in thecytoplasm attach to the ER’s surface are called rough endoplasmicreticulum. The ribosomes’ job is tomake proteins. Each protein theER makes has a specific job. Otherribosomes float freely in the cytoplasm and carry out specific tasks.The surface of the ER that does not have ribosomes attachedis called the smooth endoplasmic reticulum.
The smooth ERalso performs chemical activities. For example, it makes andstores lipids.What tasks are performed by other organelles?Once the proteins are created, they move to another organelle,the Golgi (GAWL jee) apparatus. The Golgi apparatus sortsproteins and then packs them into structures called vesicles. Thevesicles are then sent to where they are needed.Another important part of the cell is the vacuole.
A vacuole isa sac inside a membrane. Inside the vacuole, materials needed bythe cell are temporarily stored. Some vacuoles store food andenzymes. Others store waste products until they can be removedfrom the cell.Lysosomes have the job of removing the waste. They areorganelles filled with digestive enzymes. Lysosomes join a vacuoleand send their enzymes into it. The enzymes digest the contents.NucleusMitochondrionIdentify theParts Place a check markbeside each part of theeukaryotic cell in the diagramabove after you have readabout it.2.
What are the two types ofendoplasmic reticulum?________________________________________________READING ESSENTIALSChapter 775NameDateClassSection7.3Eukaryotic Cell Structure, continuedEnergy Transformers3. What do chloroplasts do?________________________________________________________________________Cells need energy to do their work. Chloroplasts and mitochondria are the organelles that provide the energy that cells need.Chloroplasts are in green plants and some protists.
They capturelight energy and change it into chemical energy. Mitochondriaare in plants and animals. They also transform energy for cells.Chloroplasts are a type of plastid. Plastids are plant organellesthat store things. Some store food, some store pigments—molecules that give color.
In fact, plastids are named for theircolor. Chloroplasts contain chlorophyll, a green pigment. It ischlorophyll that makes leaves and stems green.Plastids store energy in sugar molecule bonds. Mitochondriachange the sugar molecule bonds into other bonds that organellescan use more quickly and easily to get their energy.Like chloroplasts, mitochondria have an outer membrane and atightly folded inner membrane. Molecules for storing energy areon the surface of the folds.Inside the cell is the cytoskeleton, which supports the organellesin the cytoplasm. The cytoskeleton can be taken apart in one placeand put back together in another. When this is done it changesthe cell’s shape.4.
What is the jobof microtubules andmicrofilaments?________________________________________________________________________76Chapter 7How does the cytoskeleton help cells move?The cytoskeleton is a network of microtubules and microfilaments. Microtubules are tiny cylinders of protein. Microfilamentsare even smaller solid protein fibers.
They support the organellesand help materials move around the cell. Animal and protist cellsalso contain pairs of centrioles. Centrioles are made of microtubules. They are very important in cell division.Two other organelles made of microtubules are cilia (SIH lee uh)and flagella (fluh JEL uh). These organelles help the cell to moveand to feed. Cilia are short projections that look like hairs.
Theymove in a wavelike motion. A cell has many cilia. Flagella arelonger projections that move in a whip-like motion. A cell usuallyhas one or two flagella. In one-celled organisms the cilia and flagella are the most important ways of moving.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Organelles for Support and LocomotionNameDateClassSection7.3Eukaryotic Cell Structure, continued◗ After You ReadMini Glossarycell wall: rigid wall outside the plasma membrane for additional support and protectionGolgi apparatus: an organelle that sorts proteinsinto packages and packs them into vesicleschlorophyll: green pigment that traps lightenergy and gives leaves and stems theirgreen colorlysosome: organelles that remove waste fromthe cellchloroplast: organelles that capture light energyand convert it to chemical energychromatin: strands of DNA containing directionsfor making proteinscilia: short, hair-like projections on a cell’s surface, with an oar-like motioncytoplasm: clear, jelly-like fluid inside a cellmicrofilament: tiny, solid protein fibers that arepart of the cytoskeletonmicrotubule: thin hollow cylinders made of protein that are part of the cytoskeletonmitochondria: organelles in plants and animalsthat transform energy for the cellnucleolus: organelle within the nucleus thatmakes ribosomescytoskeleton: cell support structure within thecytoplasmplastid: a plant organelle used for storageendoplasmic reticulum: site of cellular chemicalreactionsvacuole: membrane-bound compartments fortemporary storage of materialsribosome: site where DNA makes proteinCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.flagella: longer projections on a cell’s surface,with a whip-like motion1.
Read the key terms and definitions in the Mini Glossary above. Highlight the name of anorganelle that is found in plants but not animals. Then, in the space provided, explain whatthe organelle does.________________________________________________________________________________________________________________________________________________________________________2. Choose two structures that work closely together in the cell to perform an important task ortasks. In your own words, describe in the space below what the structures do and how theydo it.
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