Objectives of diffusion, ) Explain theprocesses facilitated diffusion, andactive tfanspon. ) Pred¡ct the effectof a hypotonic, solution on hypertonic, or isotonic a ce . enter ) Discusshowlargeparticles andexitcells.
Review Vocabulary homeostasis: regulation ofthe internal environment of a cellor organism to maintain conditions for life suitable
New Vocabulary diffusion dynamic equilibrium lacilitated diffusion osmoSt5
isotonicsolution hypotonic solution hypertonic solution activetransport endocytosis exocytosrs
\! F¡gure 7.2O Diffusion causes the inksto movefromhigh-inkconcentration to low-inkconcentration untilthecolors become evenlyblendedin thewater.
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CellularTransport within the celland Cellulartransportmovessubstances fW@ movessubstances into and out of the cell. ieal-WorldReadinglink lmagine studying inyourroomwhilecookies are inthekitchen. Youprobably didn'tnotice whenthecookies wereputinto baking youcouldn't smell them.But,asthecookies baked, the theovenbecause your movement of thearoma fromthekitrhen to roomhappened through a process diffusion. called
Diffusion As the aroma of baking cookiesmakes its @..-r@ way to you, the particles are moving and colliding with eachother in the air. This happensbecausethe particles in gases,liquids, and solids are in random motion. Similarl¡ substancesdissolvedin water move constantly in random motion called Brownian motion. This random motion causesdiffusion, which is the net moyement of particles from an areawhere there are many particles ofthe substanceto an areawhere there are fewer particles ofthe substance.The amount ofa substancein a particular areais called concentration.Therefore,substancesdiffuse from areasofhigh concentration to low concentration.F¡gure 7.20 illustrates the processofdiffusion. Additional energyinput is not required for diffusion becausethe particles already are in motion. For example, ifyou drop red and blue ink into a container ofwater at opposite ends the container, which is similar to the watery enyironment of a cell,the processofdiffusion begins,asshown in Figure 7.20(A). In a short period oftime, the ink particleshavemixed asa result ofdiffusion to the point wherea purple color blend areais visible.Figure 7.20(8) shows the initial result ofthis diffusion.
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Given more time, the ink particlescontinueto mix and, in this case, continue to form the uniform purple mixture shownin Figure 7.20(C). Mixing continues until the concentrations of red ink and blue ink are the same in all areas.The final result is the purple solution. After this point, the particlescontinue to move randomly,but no further changein concentration will occur. This condition, in which there is continuous movement but no overall change,is called dynamic equilibrium. One ofthe key characteristicsof diffusion is the rate at which diffusion takes place. Three main factors affect the rate of diffusion: concentration, temperature, and pressure.When concentration is high, diffusion occurs more quickly becausethere are more particles that collide. Similarl¡ when the temperature or pressureincreases,the number of collisions increases,thus increasingthe rate ofdiffusion. Recall that at higher temperaturesparticles move faster,and at higher pressurethe particles are closer together. In both cases,more collisions occur and diffusion is faster.The size and charse of a substancealso affects the rate of diffusion.
Vocneulnnv. . . . . . . . r'.sr&e*l*er"t Ie {*{: ¡u¡}.} Conc€ntration: the amount of component in a given areaor volume. The mncentratíon of salt in the at¡uar rum wastoohígltnusingthefishes to die. . .
In addition to water, Diffusion across the plasma membrane cells need certain ions and small molecules,such as chloride ions and information Incorporate sugars,to perform cellular functions. Water can diffuse acrossthe fromth¡ssect¡on ¡nto yourFoldable. plasma membrane,as shown in Figure 7.21(4), but most other substancescannot. Another form oftransport, called facilitated diffusion, usestransport proteins to morreother ions and small moleculesacross the plasma membrane.By this method, substancesmove into the cell through a water-filled transport protein called a channel protein that opens and closesto allow the substanceto diffuse through the plasma membrane,asshownin Figure 7.21(B).Another type oftransport protein called a carrier protein also can he$ substancesdiffuse acrossthe plasmamembrane. Carrier proteins changeshapeasthe diffusion processcontinues to help move the particle through the membrane,asillustratedin F¡gure 7.21(c), Diffusion ofwater and facilitated diffusion of other substances + Figure 7.21 Although watermoves freelythroughthe plasmamembrane, other require no additional input of energy becausethe particles are moving substances cannotpassthroughthephosphofrom an area ofhigh concentration to an area oflower concentration. lipidbilayer onlheirown.suchsubstances This is also known as passivetransport. You will learn later in this secenterthecellbyfacilitated transport. tion about a form ofcellular transport that does require energyinput.
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2O2 Chapter7 . Cellular Structure andtunction
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Osmosis:Diffusion of Water Water is a substancethat passesfreely into and out of the cell through the plasma membrane. The diffusion ofwater acrossa selectivelypermeable membrane is called osmosis (ahs MOH sus). Regulating the moyement ofwater acrossthe plasma membrane is an important factor in maintaining homeostasiswithin the cell. How osmosis works Recallthat in a solution, a substancecalled the solute is dissolvedin a solvent. W a t e ri s t h es o l v e nitn a c e l la n d i l s e n v i r o n m e n l . Concentration is a measureofthe amount of solute dissolvedin a solvent.The concentration ofa solution decreases when the amount of solventincreases. Examine Figurc 7.22 showing a U-shaped tube containing solutions with different sugar concentrations separatedby a selectivelypermeable membrane. What will happen if the solvent (water) can passthrough the membrane but the solute (sugar) cannot? Water molecules diffuse toward the side with the greater sugar concentration-the right side.As water moves to the right, the concentration ofthe sugar solution decreases.The water continues to diffuse until dynamic equilibrium occurs-the concentration ofthe solutions is the same on both sides.Notice in F¡gure 7,22 that the result is an increasein solution level on the right side.During dynamic equilibrium, water molecules continue to d i f f u s eb a c ka n d f o r t h a c r o s st h e m e m b r a n eB. u t , the concentrations on eachside no longer change.
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Osmosis
What will happento cellsplacedin a strong salt solution? Regulating flow and amountof water into and out of the cellis criticalto the survivalof that cell.osmosisis one method usedto regulatea cell'swater content. Procedure 1. Readand completethe lab safetyform. 2. Preparea controlslideusingonion epidermis, water,and iodinestainas directedby your teacher. 3. Prepare a testslideusingonionepidermis, saltwateL and iodinestainasdirectedby yourteacher. 4. Predictthe effect,if any,that the saltsolution will haveon the onioncellsin the testslide. 5. Viewthe controlsl¡deusinga compound microscope underlow powerand sketch several onioncells. 6. Viewthe testslideunderthe samemagnificationand sketchyour observat¡ons. Analysls 1. Analyzeand ConcludeWasyour predictioncorrector incorrect? Explain. 2. Explain Usethe process of osmos¡s to expla¡nwhat you observe.
BeadingCheckCompareand contrast diffusion andosmosis.
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After osmosis
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Concopts|n li()t¡on of InteractiveFigure Toseean animation hypoton¡c, or hypertonic osmosis in an ¡soton¡c, v¡sitb¡oloqvgmh.com. solut¡on,
i$ Figure 7.24 In a hypoton¡c solution, waterentersa cellby osmos¡tcausing the cell to swell to swell.Animalcellsmaycontinue their untillhey burst.Plantcellsswellbeyond pressure normalsize asinternal intreases.
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Cells in an ¡soton¡c solut¡on When a cell is in a solution that has the sameconcentrationofwater and solutes-ions, sugars,proteins, and other substances-as its cytoplasm,the cell is said to be in an isotonic solution. Iso- comes from the Greek word meaning equal. Water still moves through the plasma membrane, but water enters and leavesthe cell at the samerate. The cell is at equilibrium with the solution, and there is no net movementofwater. The cellsretain their normal shape,asshown in F¡gure 7.23. Most cellsin organismsare in isotonicsolutjons,suchasblood. Cells in a hypotonic solut¡on If a cell is in a solutionthat has a lower concentration of solute, the cell is said to be in a hypotonic solution, Hypo- comes from the Greek word meaning under.There is more water outside ofthe cell than inside. Due to osmosis,the net movement of water through the plasma membrane is into the cell, as illustrated in Figure 7.24. Pressuregeneratedaswater flows through the plasma membrane is called osmotic pressure.In an animal cell, aswater moves into the cell, the pressureincreasesand the plasma membrane swells.If the solution is extremely hypotonic, the plasma membrane might be unable to withstand this pressureand the cell might burst. Becausethey have a rigid cell wal1that supports the cell, plant cells do not burst when in a hypotonic solution. As the pressureinside the cell increases,the plantb central vacuole fills with water, pushing the plasma membrane against the cell wall, shown in the plant cell inFigure 7'24. Insteadofbursting, the plant cell becomesfirmer. Grocersusethis process to keep produce looking fresh by misting fruits and vegetableswith water.
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Plant cells ,' Figure 7,25 Ina hypertonic solution, waterleaves a cellbyosmos¡s, causing thecelito shrink. Animalcellsshrivelupastheylosew¿ter. pressurq Asplantcellsloseinternal theplasma membrane shrinks awayfromthecellwall.
Cells in a hypertonic so¡ution When a cell is placed in a h lertonic solution, the concentration ofthe solute outside ofthe cell is higher than inside. Hyper comes from the Greek word meaning abol,e"During osmosis,the net movement of water is out of the cell, as illustrated in Figure 7.25, Animal cells in a hypertonic solution shrivel becauseof decreasedpressurein the cells. Plant cells in a hypertonic solution lose wate¡ mainly from the central vacuole.The plasma membrane shrinks away from the cell wall. Loss ofwater in a plant cell causeswiltinq.
Active Transport Sometimes substancesmust move from a region oflower concentration to a region ofhigher concentration against the passivemovement from higher to lower concentration. This movement ofsubstancesacrossthe plasma membrane against a concentration gradient requires energ¡ therefore, it is called active transport. F¡gure 7.26 illustrates how ¿ctive transport occurs with the aid ofcarrier proteins, commonly called pumps. Some pumps move one type ofsubstance in only one direction, while others move two substanceseither acrossthe membrane in the same direction or in opposite directions. Due to active transport,the cell maintains the properbalanceofsubstancesit needs. Active transport helps maintain homeostasis. . Figure 7.26 Carrier proteins pickupandmovesubstances across theplasma membrane gradient against theconcentration andintothecell. Cxplain Whydoes active transporf require energy?
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Na+/K+ ATPase pump One common active transport pump is called the sodium-potassium ATPasepump. This pump is found in the plasma membrane of animal cells. The pump maintains the level of sodium ions (Na*) and potassium ions (K+) inside and outside the cell. This protein pump is an enzyme that catalyzesthe breakdown of an energy-storing molecule. The pump usesthe energy in order to transport three sodium ions out ofthe cell while moving two potassium ions into the cell. The high level ofsodium on the outside ofthe cell createsa concentration gradient. Follow the stepsin Figure 7.27 to seethe action ofthe Na+/K+ATPasepump. T h e a c t i v i t yo l t h e N a / K A T P a speu m p c a n r e s u l il n yet another form ofcellular transport. Substances,such as sugar molecules,must come into the cell from the outside,where the concentration ofthe substanceis lower than inside. This requires energ¡ Recall,howeve¡ that the Na+/K+ATPasepump moves Na+ out of the cel1, which createsa low concentration of Na+ inside the cell. In a processcalled coupled transport, the Na+ ions that havebeen pumped out ofthe cell can couple with sugar moleculesand be transported into the cell through a membrane protein called a coupled channel. The sugar molecule, coupled to a Na+ ion, entersthe cell by facilitated diffusion of the sodium, as shown in Figure 7.28. As a result, sugar entersthe cell without spending any additional cellular enersy.
$ i, F¡gure 7.28 Substances "piggy'back" the¡rway¡ntoor out of a cellby coupl¡ng pump. w¡thanothersubstance thatusesan act¡vetransport Compare and conlfa9l active and passivetransport acrossthe plasmamembfane. 206
Chapler7 . Cellular Structure andFunction
Endocytos¡s
Exocytosis Outside the cell
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Transportof Large Particles Somesubstancesare too large to move through the plasmamembrane by diffusion or transport proteins and get inside the cell by a different process.Endocytosis is the processby which a cell surrounds a substance in the outsideenvironment, enclosingthe substancein a portion ofthe plasmamembrane.The membrane then pinchesoff and leavesthe substanceinside the cell. The substanceshown on the left in Figure 7,29 is engulfed and enclosedby a portion of the cell'splasmamembrane.The membrane then pinches offinside ofthe cell and the resulting vacuole, with its contents,movesto the inside ofthe cell. Exocytosis is the secretion of materials at the plasma membrane. The illustration on the right in Figure 7.29 showsthat exocytosisis the reverse ofendocytosis.Cells useexocytosisto expelwastesand to secretesubstances,such ashormones,producedby the cell. Both endocytosisand exocytosisrequire the input of energy.Cells maintain homeostasisby moving substancesinto and out ofthe cell. Sometransport processes require additional energyinput, while othersdo not. Together,the different types oftransport allow a cell to interact with its environment while maintainins homeostasis.
,. Figure 7.29 Lefl: Largesubstances canentera cellby enoocytQsrs. R¡ght:Substances canbedeposited outside the cellbyexocytosis.
Scqtis&7A-4 Section Summary homeostasis us¡ng ) Cellsmaintain cassive andactivetransport. temperature, and ) Concentration, pressure affectthe rateof diffusion. homeostasis in I Cellsmustmaintain alltypesof solutions, ¡nclud¡ng isoton¡c,hypotonic, andhypertonic.
Understand Main ldeas 1. :'i,':::;i,K@ List and describe thetypesof cellular transport. mem2. Describehowtheplasma branecontrols whatgoesintoand comes outof a cell. 3. Sketch a beforeandanafterdiagramof ananimalcellplaced in a hypotonic solut¡on.
aremovedinto ) Somelargemolecules diffuandoutof thecellusingendocytosis 4. Contrast Howisfacllitated sion different from act¡ve transport? andexocytosis.
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5, Desorüo Someorgan¡sms that normally livein pondwatercontain pumps These waterpumps. continupump ally wateroutof thecell. Describe a scenario thatmight reverse the act¡onof the pump. 6, lu,tat tLa.dz.otheroleof the phospholipid bilayer in cellular transport in livingcells.
ANOTECHNOLOGY
lmagine thatcancercellscouldbedetected anddestroyed onebyone,or thata new drugcouldbetestedon a singlecellto evaluateits clinicalperformance. Advances in technologies thatallowscientists to focuson individual cellsmightmakethesescenarios a realityin thenearfuture. (nanotek NAWluhjee)isthebranch Nanotechnology of science thatdealswithdevelopment anduseof devices (nm)is one onthenanometer scale.A nanometer billionth of a meter(10 e m).Toputthisscaleinto perspective, consider thatmosthumancellsarebetween 10,000 and20,000nm in diameter. Nanotechnology is a fast-growing branch of science thatlikelywillleaveits markon everything fromelectronics to medicine.
Thiscomputergenefated lmage shows a nafobotarmed witha bio chip.Someday, a biochip, whichis¿ne ectfonic devlce thatcontains ofganc materia s,mightrepar a damaged nerve cel.
Lasers Nanotechnology perhaps applications, in the formof nanosurgery, couldbeusedto investigate how cellsworkorto destroy individual cancer cellswithout Atomic force microscopes ArtheNational harming nearby healthy cells.Researchers at Harvard Institute of Advanced Industrial Science andTechnology University havedeveloped a lasertechnique thatallows in Hyogo, Japan, researchers areusingnanotechnology in themto manipulate a specific component of thecell's (AFM)to operate theformof an atomicforcemicroscope partswithoutcausing internal damage to thecell on singlecells.Themicroscope is actually usedasa membrane or othercellstructures" lmagine having the "nanoneedle." TheAFMcreates a visualimageof a cell capability to perform extremely delicate surgery on a usinga microscopic sensor thatscans thecell-Thenthe cellular levell probeof theAFM,sharpened intoa needle tip thatis approximately 200nmin diameter, canbeinserted into ln thefuture,nanotechnology mightbeourfirstline thecellwithoutdamaging thecellmembrane. of defense to treatcancer. lt alsomightbecome the Some scientists envision manyapplications forthistechnique. Thenanoneedle mighthelpscientists studyhowa cellresponds to a newdrugor howthechemistry of a diseased celldiffersfromthatof a healthy cell.Another application forthenanoneedle m¡ghtbeto ¡nsertDNA strands directly intothenucleus of a cellto testnewgene therapy techniques genetic thatmightcorrect disorders.
2O8 Chapter7 . Cellular Structure
standard technique to testnewdrugsor evenbecome a favored treatment usedin genetherapy.
@ntrEi@Biolosy ReviewVisitbioloqvqmh.com to learnmoreaboutnanotechnology in medicine andhealthcare.Writeanoverviewof onetechnology thatyoufindinteresting. Describe ¡tsadvantages andchallenges. Youmayinclude a presentat¡onw¡thyouroverview.
tsIOLAB WHICHSUBSTANCES WILLPASSTHROUGH A SEMIPERMEABLE MIMBRANE? Background:All membranes in cells, including theplasma membrane andthe membranes thatsurround organelles in permeable. eukaryotic cellt areselectively In thislab,youwill examine themovement of somebiologically important molecules througha dialysis membrane thatis analogousto theplasma membrane. Because a dialysis membrane hastinypores,it isonly permeable for tiny molecules. passthrougha Question: Whichsubstances dialvsis membrane?
Materials cellulosedialysis tubing (2) 400-rnl beakers(2) stnng scissors distilled water small plastic dishpan starchsolution albumin solution glucosesolution NaCl solution iodine solution (testsstarch)
anhydrousBenedict's reagent(tests glucose) silver nitrate solution (testsNaCl) biuret reagent(tests albumin) 10-mL graduated cylinder test tubes (2) test-tube rack funnel eyedroppers
SafetyPrecautions
@tr @ FiEEzt¿ GlE Procedure l. Readand completethe lab safetyform. 2. Construct a data table asinstructed by your teacher. Collect two lengthsof dialysistubing, two 400-mL beakers,and the two solutions that you havebeen assignedto test. 4. Labelthe beakerswith the type of solution that you placein the dialysistubing.
5. With a partner,prepareand frll one length of dialysistubing with one solution. Rinse the outside of the bag thoroughly. Place the filled tubing bag into a beakerthat containsdistilled water. 6. Repeatstep 5 using the secondsolution. 7. After 45 minutes, transfer some of the water ftom eachbeakerinto separate testtubes. 8. Add a fewdropsof the appropr¡atetest reagentto the water. 9 . R e c o r dy o u r r e s u l l sa n dd e t e r m i n e whether your prediction was correct. Compareyour resultswith other groups in your classand record the resultsfor the two solutions that you did not test. 10. Cleanup and Disposal Washand return all reusablematerials.Disposeof test solutions and useddialysistubing asdirected by your teacher.Washyour handsthoroughly after using any chemical reagent.
Analyze andConclude l . Evaluate Did your test moleculespass t h r o u g ht h ed i a l y s i tsu b i n g ?E x p l a i n . 2 . Think Critically What characteristicsof a plasmamembranegive it more control over the movement of moleculesthan the dialysismembrane? 3. Error Analysis How could failing to rinse the dialysistube bagswith distilled water prior to placing them in the beakercausea falsepositive test for the presenceof a dissolvedmolecule?What other sourcesof error might lead to inaccurateresults? . , , - - - , , - .:. . - - . - . - , - - ;. .: ,: .: - i ., : - : - :
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POSTER SESSION Commun¡cate A diseasecalledcystic fibrosis occurswhen plasmamembraneslack a molecule which helps transport chloride ions. Research this diseaseat bioloqvqmh.com and presentyour finding your poster to classusing a or a brochure. .
B¡oLab 2O9
tilMi4g'- applyUsewhatyouhave learned about osmosis andcellular transport to design anappafishto survive ina saltwafer habitat. ratus thatwould enable a freshwater Key Concepts cell(p.182) (p.183) celltheory eukaryot¡c cell(p.186) (p.186) nucleus organelle 0. r86) plasma (p.185) membrane prokaryotic cell{p.186)
The invention of the microscope led to the discovery of cells. tr;íAIK@ . Microscopeshave been used asa tool for scientific study sinceüe late 1500s. . Scientists use different types of microscopes to study cells. . The cell theory summarizesthree principles, . There are two broad groups of cell q'pes-pmkaryotic cellsand eukaryotic cells. . Eukaryotic cells contain a nucleus and organelles,
fluid mosaicmodel (p. |90) phospholipid bilayer(p.188) select¡vepermeability(p. 187) transportprote¡n(p. 189)
The plasma membrane helps to maintain a cell's homeostasis. WffiK@ . Selectivepermeability is the property of the plasma membrane that allows it to control ¡ ¡hat enters and leavesthe cell. . The plasma membrane is made up of two layers of phospholipid molecules. . Cholesterol a¡d transpof proteins aid in the function ofthe plasma membrane. . The fluid mosaic rnodel describesthe plasmamembra¡e.
cellwall (p.198) centriole(p.196) (p.197) chloroplast cilium(p.198) (p"191) cytoplasm (p.191) cytoskeleton (p.194) endoplasmic reticulum (p.198) flagellum (p.195) Golgiapparatus (p.196) lysosome (p"197) mitochondr¡on (p.193) nucleolus (p.193) ribosome (p.195) vacuole
Eukaryotic cells contain organelles that allow the specialization fgffiK@ and the separation of functions within the cell. . Eukaryotic cells contain me¡nbrane-bound organelles in the cltoplasm that perform cell functions. . Ribosomes are the sites of protein synthesis. . Mitochondria are the powerhouses of cells, . Plant and animal cells contain many of the same organelles, while other organelles are unique to either plant cells or animal cells.
activetransport(p.205) (p.201) diffusion (p.202) dynamic equilibrium (p.207) endocytos¡s (p.207) exocytosis fac¡litated diffusion(p.202) hyperton¡c solution(p.205) hypotonic solut¡on(p.204) ¡sotonic solution(p.204) (p.203) osmosis
Cellular transport moves substanceswithin the cell and moves WW@ substancesinto arid out of the cell. . Cells maintain homeostasis using passiye and active transport. . Concentration, temperature, and pressure affect the rate of üffusion. . Cells must maintain homeostasis in all types of solutions, including isolonic,hypotonic,and hl?ertonic. . Some large molecules are moved into and out of the cell using endocytosis and exocltosis.
2tO Chapter 7. Study Guide
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Vocabulary
Key Concepts
cell(p.182) celltheory(p.183) eukaryotic cell(p.186) (p.186) nucleus (p.186) organelle plasma (p.185) membran€ prokaryotic cell(p.186)
The invention of the microscope led to the discovery of cells. WWffi@ . Microscopeshavebeen used asa tool for scientific study sincethe late 1500s, . Scientists use different t).pes of microscopes to study cells. . The cell theory summarizes three principles. . There are two broad groups of cell qpes-prokaryoüc cellsand eukaryotic cells, . Elkaryotic cells contain a nucleus and organelles,
fluid mosaicmodel(p. 190) phospholipid b¡layer(p. 188) selectivepermeab¡l¡ty(p. 187) transportprotein (p. 189)
The plasma rnembrane helps to maintain a cell's homeostasis. Itr;Í#K@ . Selective permeability is the property of the plasma membrane that allows it to control what enters and leavesthe cell. . The plasma membrane is made up of two layers of phospholipid molecules. . Cholesteroland transport proteins aid in the function ofthe plasmamembrane. . The fluid mosaic model describesthe plasmamembrane.
cellwall (p. 198) centriole(p. 196) '197) chloroplast(p. c¡lium(p. 198) cytoplasm(p. f91) (p. 191) cytoskeleton (p.194) ret¡culum endoplasmic tlagellum(p. 198) Golg¡apparatus(p. 195) lysosome(p. 196) (p. 197) mitochondrion (p. 193) nucleolus (p. 193) ribosome vacuole(p. 195)
lffiXK@ Eukaryotic cells contain organelles that allow the specialization and the separation of functions within the cell. . Eukaryotic cells contain membrane-bound organelles in the cytoplasm that perform cell functions. . Ribosomes are the sites of protein sl.nthesis. . Mitochondria are the powerhousesof cells. . Plant and anirnal cells contain many of the same organelles, while other organelles are unique to either plant cells or animal cells.
activetransport(p.205) difiusion(p.201) (p.202) dynamic equ¡librium (p.207) endocytos¡s (p,207) exocytosis facil¡tated diffusion(p.202) hyperton¡c solution(p.205) hypotonic solution(p.204) ¡sotonic solution(p.204) (p.203) osmosis
Cellular transport moves substanceswithin the cell and moves trffi@ substancesinto and out of the cell. . Cells maintain homeostasis using passiye and active transport. . Concentration, temperature, and pressure affect the rate of diffusion. . Cells must maintain homeostasis in all types of solutions, including isoton¡c,h)?oton¡c,and hypertonic. . Some large molecules a¡e moved into and out of the cell using endoc¡osis and exocltosis.
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8. Short Answer Compareand contrastprokaryotic cellsand eukaryoticcells.
Review
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9. CARIIüRS IN BIOLüGY Why might a microscopist,who specializesin the use of microscopes to examinespecimens,use a light microscope insteadof an electronmicroscope?
L The nucleusis a structure that surrounds a cell and helps control what entersand exits the cell.
10. Analyze A material is found in an asteroidÍhat might be a celi.What criteria must the material meet to be considereda cell?
2. L(n) prokaryof¿has membrane-bound organelles. 3. Organelles arebasicunits o[ all organisms.
Understand KeyConcepts 4. If a microscope hasa seriesof threelensesthat magnift individually5x, 5x, and 7x, whatis the total magnificationwhenlookingthroughthe microscope? A- Z5x C. 17x 8.35X D. I75x 5. \44rich is not part of the ceil theory? A. The basicunit of life is rhe cell. B. Cellscame from preexistingcells. C. A1l living organismsare composedof cells. D, Cejls contain membrane-bound organelles.
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, VocabularyReview thesentences belowusingvocabulary terms 1 Complete page. the Guide Study i from is thebasicstructuremoleculemakI f t. ¡ ing up the plasmamembrane. The all cells,
is the component that surrounds
is the propertF that allowsonly some substancesin and out of a cell.
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6. The photomicrograph showswhich kind of cell? A- prokaryotic cell C, animal cell B. eukaryotic cell D. plant cell
Constructed Response 7. Open Ended Explain how the developmentofthe microscopechangedhow scientistsstudiedliving organisms.
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ConstructedResponse
26. Where are the ribosomesproduced? ,A. nuclear pore B. nucleolus C. chromatin D. endoplasmicreticulum
16. Short Answer Explain how the plasmamembrane maintains homeostasiswithin a cell. 17, Open Ended Explain what a mosaicis and then explain why the term lluid mosaicmod¿lis usedto describethe plasmamembrane.
27. In which structure would you expect to find a cell wall? A. a human skin cell B. a cell from an oak tree C. a blood cell from a cat D. a liver cell from a mouse
18. Short Answer How doesthe orientation of the phospholipids in the bilayer allow a cell to interact with its internal and externalenvironments?
rhink Critically
ConstructedResponse
Hypothesize how a cell would be affectedif it lost the ability to be selectivelypermeable.
28. Short Answer Describe why the cytoskeleton within the cytoplasmwas a recentdiscovery.
Predict What might happen to a cell if it no longer could produce cholesterol?
29. Shofi Answer Comparethe structuresand functions of the mitochondrion and chloroplastbelow.
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VocabularyReview Fill in the blank with the vocabularytermfrom the Study Guidepagethat matchesthefunction definition. 21. -
storeswastes
22, -
producesribosomes
23, -
generales energyfor a cell
24, -
sortsproteins into vesicles
30. Open Ended Suggesta reasonwhy packetsof proteins collectedin a vacuolemight mergewith lysosomes.
ThinkCrit-cally
Understandfey Concepts
31. Identify a specific example where the cell wall structure has aided the survival of a plant in its natural habitat.
25 and26. Usethediagrambelowto answerquestions pore Nuclear Chromalin Nucleolus
Endoplasmic reticulum
: 32. Infer Explain why plant cellsthat transport water againstthe force of gravity contain many more : : mitochondria than other plant cells. ;
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i VocabularyReview Ribosome
Explain the differencein the termsgiven below.Then 1 explainhow the termsare related. :
proteins that will be 25. Which structure sl.nthesizes : 33, activetransport, facilitateddiffirsion usedby the cell? I 34. endocytosis,exoc¡osis ,d chromatin C. ribosome B. nucleolus D, endoplasmicreticulum , 35. hlpertonic solution, hlpotonic solution 212 ChapterT.Assessment
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UnderstandKeyConcepts 36. Which is not a factor that affectsthe rate of
diffusion? A. conductivity B. concentration
C. pressure D. temperature
37. Which type of transport requiresenergyinput from the cell? A. activetransport B. facilitated diffusion C. osmosis D. simple diffirsion
Response Constructed
$. @Biology Createa poemthat decribesthe functionsof at leastfivecell organelles.
Document-Based Questions
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Thegraph belawdestibes the relaüonshipbetweenthe amount of glucoseenteringa cell and the rate at which theglucoseentersthe cell with the help of carrier proteirc. Usethis graph to answerquestions44 and 45. Dataobtained fom:Raven, PH.,andlohnson, 6.B.2002.,/b/ogy,6thed.i99.
3E. Short Answer Why is activetransport an energyutilizing process? 39. Short Answer Some protists that live in a hlpotonic pond environment havecell membrane adaptationsthat slow water uptake.What adaptations might this protist living in the hlpertonic Great Salt Lake have?
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AmoÍnt of glu(ose 44. Summarizethe relationshipbetweenthe amount of glucoseand the rate of diffr¡sion.
40. Short Answer: Summarizehow cellular transport helps maintain homeostasiswithin a cell.
45. Infer why the rate of diffirsion tapersoffwith higher amounts of glucose.Make an illustration to explain your answer.
Cumulative Review ThinkCritically 41, Hypothesize how or.ygencrossesthe plasma membrane if the concentrationof orygen is lower inside the cell than it is outside the cell. 42, Analyze Farming and watering that is done in very dry regions ofthe world leavessaltsthat accumulatein the soil aswater evaporates.Based on what you know about concentrationgradients, why doesincreasingsoil salinity haveadverse effectson plant cells? d.
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46, Rabbits were introduced into Australia in the I 800s.The population of rabbits grew unchecked. Explain why this occurred and how this could (chapteri) adverselyaffectan ecosystem. 47. Ngae are a group of plantlike organisms. Many of üese organismsproduce their own food by . photosynthesis.Are theseorganismsautotrophs or heterotrophs?Explain.(Chapter2)
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ChapterT.Assessment 2t3
Standardized,Ibst Practice Cumulative
Usethe illustration belowto answerquestions1 and 2.
5, Which is a nonrenewableresource? A. cleanwater from freshwatersc¡urces B. energyprovided by the Sun C. an animal speciesthat hasbecomeextinct D. a type offish that is caüght in the ocean
Which number in the illustration representsthe location whereyou would expectto find water-insoluble substances? 4. 1 8.2
c.3 D.4
Which is the effect ofhaving the polar and nonpolar ends ofphospholipid moleculesori€nted as they are in this illustration? A. It allows transport proteins to move easily through the membrane. B. It controls the movement ofsubstancesacrossth€ membrane. C. It helps the cell to maintain its characteristic shape. D. It makesmore room inside the phospholipid bilayer.
Which of thesehabitatswould be best suited for a population of r-strategists? A' desert B.: grassland C. deciduousforest D. tropical rain forest
Which adaptationhelpsplants survive in a tundra biome? A, deciduousleavesthat fall off aswinter approaches B, leavesthat storewater C. roots that grow only a few centimetersdeep D. underground st€msthat are protectedftom orazino,rnim¡ls
2'14 Chapter7. Assessment
Usethis incompleteequationto answerquestions6 and 7.
CHa+ 4Cl2 )-HCl +-CCl4 6. The chemical equation aboveshowswhat can happen in a reaction betweenmethane and chlorine gas. The coefficientshavebeenleft out in the product side ofthe equation.Which is the correct coefficient. for HCI? A. 1 8.2
c.4 D.8
7, Which is the minimum number of chlorine (Cl) atoms neededfor the reaction shown in the equation? A. 1 8.2
c.4 D.8
8. Why is Caulerpa taxifolia considered an invasive speciesin somecoastalareasof North America? A. It is dangerousto humans. B. It is nonnativeto the ar€a. C. It grows slowly and invadesover time. D. It outcompetesnative speciesfor resources.
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9. Use a flowchart to organizeinformation about cell organellesand protein synthesis.For eachstep,analyze the role ofthe organell€in protein synthesis.
The illustraüon belowshowsa singleanimal cellin an isotonicsolutinn. Usethe illustratinn to answerquation 16.
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10. Compareand contrasithe functions ofcarbohydrates,lipids, proteins,and nucleicacids.
16. Describewhat would happen to this cell in a hypertonic solution and in a hypotonic solution.
ll. Statewhy the polarity ofwater moleculesmakes water a good solYent.
17. Explain why direct economicvalue is not the only important considerationwhen rt comesto biodiversity.
Usethefigure belowto answerquestion12.
18. Analyze why an electron microscopecan produce higher magnification than a light microscope. 19. Assesswhy transport proteins are neededto move certain substancesacrossa cell membrane.
KCt Atom¡c number 19
Atomic number 17
Recentl¡ some international trade agreementshave allowed scientistsand companiesto patent the discoveriesthey make about organismsand their genetic material. For instance,it is possibleto patent seedsthat havegenesfor diseaseresistanceor plants that can be usedin medicine or industry Owners of a patent then havegreatercontrol over the useofthese organisms.
12, Use the figure to describehow the ionic compound potassium chloride (KCl) is formed.
13. What might happen if cell membraneswere not selectivelypermeable?
Usingthe information in theparagraphabove,answerthe followi ng question i n essay for mat.
14. Choosea specific natural resourceand developa plan for the sustainableuse of that resource. .
20. Basedon what you know about biodiversit¡ identify somepros and cons for a patent system.Write an essayexploring the pros and cons ofpatenting discoveries aboutorganisms.
15, What can you infer about the evolution ofbacterial cells from studying their structure?
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ChapterT.Assessment 215