Reading Essentials for Biology Glencoe (794133), страница 21
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Be sure to tell how the work of one structure relates to the work of the other.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________READING ESSENTIALSChapter 777NameDateClassSection7.3Eukaryotic Cell Structure, continued3. Use the chart to help you review what you have learned.
Identify the structure and specifictask for the various parts of a eukaryotic cell.Eukaryotic Cell StructureCell PartStructureTaskcell wallchromatinnucleusnucleolusribosomescytoplasmnuclear envelopeendoplasmic reticulumGolgi apparatusvacuolelysosome78Chapter 7Copyright © 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 eukaryotic cell structure.READING ESSENTIALSNameDateClassSection8.1 Cellular TransportSC.F.1.4.8 The student knows that cell behavior can be affected by molecules from other parts of the organism or evenfrom other organisms.◗ Before You ReadThis section is about cell transport.
You will learn how substances move in and out of cells. Thinkabout the ways you have seen things being moved from place to place. When are things easily transported? When it is more difficult, what types of equipment might be used to help move thingsalong? Write your thoughts on the lines below.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Osmosis: Diffusion of WaterThe plasma membrane of a cell is called a selectively permeablemembrane. This means only certain particles, or molecules, arelet in and out of a cell.Water is the only substance the plasma membrane always allowsin or out.
The movement of water from an area of higher concentration to an area of lower concentration, or diffusion, across theplasma membrane is called osmosis (ahs MOH sus). This waterflow through the membrane helps create homeostasis. Homeostasis is the regulation of the cell’s internal environment.Read forUnderstanding As you readthis section, highlight any sentence that you reread.
Rereadany sentences you highlighted.How does osmosis affect cells?Most cells undergo osmosis because they are floating in watersolutions. When a cell is floating in an isotonic solution, the watermoves in and out of the cells at the same rate. In an isotonicsolution, dissolved substances inside and outside of the cell havethe same concentration. Because the amount of water moving inand out of the cells is the same, the cells keep their normal shape.When a cell is floating in a hypotonic solution, more waterenters the cell through osmosis than leaves it. In a hypotonicsolution, the concentration of dissolved substances is lower outside of the cell than inside.
The cell swells because of the extrawater that enters. As a result, the cell’s internal pressure increases.In a hypertonic solution, water moves out of the cell duringosmosis. When a cell is floating in a hypertonic solution, theconcentration of dissolved substances outside of the cell is higherREADING ESSENTIALS1. What is the term for theflow of water across theplasma membrane?________________________________________________________________________Chapter 879NameDateClassSection8.1Cellular Transport, continuedCell after being placedin an isotonic solutionWater moleculeCell after being placedin a hypotonic solutionCell after being placedin a hypertonic solutionDissolved particlethan inside of the cell. As water leaves the cell, the cell shrinks,and the pressure inside of the cell decreases.________________________________________________________________________Passive TransportSome molecules, like water, can pass through the plasma membrane by simple diffusion.
When the cell uses no energy to movesuch particles, the movement is called passive transport.Special proteins in the plasma membrane move materials acrossthe membrane. These are called transport proteins. When transport proteins help the passive transport of materials, the processis called facilitated diffusion.Active TransportIn active transport, a transport protein called a carrier proteinhelps move particles across the membrane against a force.
Thatforce is called a concentration gradient. A concentration gradientdevelops when there are more molecules on one side of a membrane than the other. Because the transport protein has to workhard against the concentration gradient, energy is needed for thecarrier protein to move the particles.
The transport of substancesacross cell membranes is what helps cells maintain homeostasis.Transport of Large ParticlesEndocytosis (en doh si TOH sus) is the process in which a celltakes in material from its surroundings and then releases thematerial inside the cell. During endocytosis, a cell surrounds andtakes in material from its environment. This material does notpass directly through the membrane. Instead, it is engulfed andenclosed by a portion of the cell’s plasma membrane.
It thenbreaks away and moves to the inside of the cell.80Chapter 8READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.2. What is the movementcalled when a cell doesnot use energy to moveparticles across the cell’smembrane?NameDateClassSection8.1Cellular Transport, continuedExocytosis is the reverse process of endocytosis. It is the processof a cell taking material from inside itself and secreting or expellingit from the cell. The material can be wastes or other chemicals.The figure below illustrates endocytosis and exocytosis.Some unicellular organisms ingest foodby endocytosis.
They release wastes orcell products by exocytosis.NucleusWastesDigestionExocytosisCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Endocytosis◗ After You ReadMini Glossaryactive transport: energy-needing process bywhich cells transport materials across the cellmembrane against a concentration gradientendocytosis (en doh si TOH sus): active transportprocess where a cell engulfs materials witha portion of the cell’s plasma membraneand releases the contents within the cellexocytosis: active transport process by whichmaterials are secreted or expelled from a cellfacilitated diffusion: passive transport of materials across a plasma membrane by transportproteins embedded in the plasma membranehypertonic solution: in cells, solution in whichthe concentration of dissolved substancesoutside the cell is higher than the concentration inside the cell; causes a cell to shrinkas water leavesREADING ESSENTIALShypotonic solution: in cells, solution in which theconcentration of dissolved substances islower in the solution outside the cell thanthe concentration inside the cell; causes acell to swell and possibly burst as waterenters the cellisotonic solution: in cells, solution in which theconcentration of dissolved substances in thesolution is the same as the concentration ofdissolved substances inside a cellosmosis (ahs MOH sus): diffusion of water acrossa selectively permeable membrane depending on the concentration of solutes oneither side of the membranepassive transport: movement of particles acrosscell membranes by diffusion or osmosis;the cell uses no energy to move particlesacross the membraneChapter 881NameDateClassSection8.1Cellular Transport, continued1.
Highlight two terms in the Mini Glossary on page 81 that identify specific types of activecell transport.2. Use the Venn diagram to help you review what you have read about cell transport.Characteristics ofFacilitated DiffusionCharacteristics ofActive TransportCharacteristics of Both3. Choose one of the main headings in the Read to Learn section. Change the heading into aquestion and write it in the space below. Then write your answer to that question on thelines that follow.Answer:____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Visit the Glencoe Science Web site at science.glencoe.comto find your book and learn more about cellular transport.82Chapter 8READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Question:NameDateClassSection8.2 Cell Growth and Reproduction◗ Before You ReadSC.F.1.4.8 The student knows that cell behavior can be affected by molecules from otherparts of the organism or even from other organisms.
SC.F.2.4.2 The student knows thatevery cell contains a “blueprint” coded in DNA molecules that specify how proteins areassembled to regulate cells.In this section you will learn about the way cells grow and divide. Have you ever watched someonetrim a bush or a tree? What would have happened if the bush or tree had not been trimmed? Writedown a few of your thoughts on the lines below.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCell Size LimitationsCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.As you have learned, the plasma membrane lets nutrients intothe cell and allows wastes to leave.
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