Chapter 9: Energy in a Cell - bcsc.k12.in.us · active transport:movement of materials through a...

What You’ll Learn■ You will recognize why organ-

isms need a constant supply ofenergy and where that energycomes from.

■ You will identify how cells storeand release energy as ATP.

■ You will describe the pathwaysby which cells obtain energy.

■ You will compare ATP produc-tion in mitochondria and inchloroplasts.

Why It’s ImportantEvery cell in your body needsenergy in order to function. The energy your cells store is the fuel for basic body functionssuch as walking and breathing.

Energy in a CellEnergy in a Cell

Johann Schumacher/Peter Arnold, Inc.

Visit to• study the entire chapter

online• access Web Links for more

information and activities oncell energy

• review content with theInteractive Tutor and self-check quizzes

This squirrel is eating seeds produced by the conifer. Theconifer traps light energy andstores it in the bonds of certainmolecules for later use. How dothe squirrel’s cells, which cannottrap light energy, use the mole-cules in the seeds to supplyenergy for the squirrel?

Understandingthe Photo

220

in.bdol.glencoe.com

0220 C9CO BDOL-829900 8/4/04 4:23 AM Page 220

http://in.bdol.glencoe.com

9.1SECTION PREVIEWObjectivesExplain why organismsneed a supply of energy.Describe how energy isstored and released by ATP.

Review Vocabularyactive transport: movement

of materials through amembrane against a concentration gradient;requires energy from the cell (p. 199)

New VocabularyATP (adenosine triphosphate)

ADP (adenosine diphosphate)

9.1 THE NEED FOR ENERGY 221

Why ATP?Using an Analogy A spring stores energywhen it is compressed. When the com-pressed spring is released, energy also isreleased, energy that sends this smiley-faced toy flying into the air. Likethis coiled spring, chemical bondsstore energy that can be releasedwhen the bond is broken. Just assome springs are tighter than oth-ers, some chemical bonds storemore energy than others.Summarize Scan this section and make a list of general ways in which cells use energy.

The Need for Energy

Stored energy

Cell EnergyEnergy is essential to life. All living

organisms must be able to obtain energyfrom the environment in which they live.Plants and other green organisms are ableto trap the light energy in sunlight andstore it in the bonds of certain moleculesfor later use. Other organisms, such as thepanda shown in Figure 9.1, cannot usesunlight directly. Instead, they eat greenplants. In that way, they obtain the energystored in plants.

Work and the need for energyYou’ve learned about several cell

processes that require energy. Activetransport, cell division, movement of fla-gella or cilia, and the production, trans-port, and storage of proteins are someexamples. You can probably come up withother examples of biological work, such asmuscles contracting during exercise, your

Figure 9.1Because this pandacannot trap thesun’s energy foruse in its body, iteats bamboo.Molecules in bam-boo leaves containenergy in theirchemical bonds.Some of thosemolecules supplyenergy for thepanda.

(tl tr)Aaron Haupt, (bl)Tom McHugh/Photo Researchers

Standard B.1.9 Recognize and describethat both living and nonliving things are composed of compounds, … joined by energy-containing bonds, such as those in ATP.

Indiana Standards

0221-0224 C9S1 BDOL-829900 8/4/04 4:29 AM 21

heart pumping and your brain control-ling your entire body. This work can-not be done without energy.

When you finish strenuous physi-cal exercise, such as running crosscountry, your body needs a quicksource of energy, so you may eat agranola bar. On a cellular level, thereis a molecule in your cells that is aquick source of energy for anyorganelle in the cell that needs it.

This energy is stored in the chemicalbonds of the molecule and can beused quickly and easily by the cell.

The name of this energy moleculeis adenosine triphosphate (uh DEH

nuh seen • tri FAHS fayt), or ATP forshort. ATP is composed of an adeno-sine molecule with three phosphategroups attached. Recall that phos-phate groups are charged particles,and remember that particles with thesame charge do not like being tooclose to each other.

Forming and Breaking Down ATP

The charged phosphate groups actlike the positive poles of two mag-nets. If like poles of a magnet areplaced next to each other, it is diffi-cult to force the magnets together.Likewise, bonding three phosphategroups to form adenosine triphos-phate requires considerable energy.When only one phosphate groupbonds, a small amount of energy isrequired and the chemical bond doesnot store much energy. This mole-cule is called adenosine monophos-phate (AMP). When a secondphosphate group is added, moreenergy is required to force the twogroups together. This molecule iscalled adenosine diphosphate, orADP. An even greater amount ofenergy is required to force a thirdcharged phosphate group closeenough to the other two to form abond. When this bond is broken,energy is released.

The energy of ATP becomes avail-able to a cell when the molecule is broken down. In other words, whenthe chemical bond between the sec-ond and third phosphate groups inATP is broken, energy is released andthe resulting molecule is ADP. At this

222 ENERGY IN A CELLMel Victor/The Stock Shop

mono-, di-, tri- fromthe Greek wordsmono and di, andthe Latin word tri,meaning “one,”“two,” and “three,”respectively;Adenosine triphos-phate contains threephosphate groups.

Recognize Cause and EffectWhy is fat the choice?Humans store their excess energy as fat rather than as car-bohydrates. Why is this? From an evolutionary and efficiencypoint of view, fats are better for storage than carbohydrates. Find out why.

Solve the ProblemThe following facts compare certain characteristics of fats andcarbohydrates:A. When broken down by the body, each six-carbon molecule

of fat yields 51 ATP molecules. Each six-carbon carbo-hydrate molecule yields 36 ATP molecules.

B. Carbohydrates bind and store water. The metabolism ofwater yields no ATP. Fat has no water bound to it.

C. An adult who weighs 70 kg can survive on the energyderived from stored fat for 30 days without eating. Thesame person would have to weigh nearly 140 kg to survive30 days on stored carbohydrates.

Thinking Critically1. Analyze From an ATP production viewpoint, use fact B

to make a statement regarding the efficiency of fats vs. carbohydrates.

2. Define Operationally Explain why the average weightfor humans is close to 70 kg and not 140 kg.

0221-0224 C9S1 BDOL-829900 8/4/04 4:30 AM Page 222

point, ADP can form ATP again bybonding with another phosphategroup. This process creates a renew-able cycle of ATP formation andbreakdown. Figure 9.2A illustratesthe chemical reactions that areinvolved in the cycle.

The formation/breakdown recy-cling activity is important because itrelieves the cell of having to store allof the ATP it needs. As long as phos-phate groups are available, the cellcan make more ATP. Another benefitof the formation/breakdown cycle isthat ADP also can be used as anenergy source. Although most cellfunctions require the amount ofenergy in ATP, some cell functions donot require as much energy and canuse the energy stored in ADP. Readthe Problem-Solving Lab on the oppo-site page and think about how thehuman body stores energy.

How cells tap into the energystored in ATP

When ATP is broken down and theenergy is released, as shown in Figure 9.2B, the energy must be cap-tured and used efficiently by cells.Otherwise, it is wasted. ATP is a smallmolecule. Many proteins have a spe-cific site where ATP can bind. Then,when the phosphate bond is brokenand the energy released, the cell canuse the energy for activities such asmaking a protein or transporting mol-ecules through the plasma membrane.This cellular process is similar to theway energy in batteries is used by aradio. Batteries sitting on a table are oflittle use if the energy stored withinthe batteries cannot be accessed.When the batteries are snapped intothe holder in the radio, the radio thenhas access to the stored energy andcan use it. When the energy in the

9.1 THE NEED FOR ENERGY 223

ADP

ADP

ATP

Adenosine

Protein

P P P

P

P

P

Adenosine P P

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

+ Energy

The addition and release of a phosphate group onadenosine diphosphate creates a cycle of ATP forma-tion and breakdown.

A To access the energy stored in ATP, proteins bind ATPand uncouple the phosphate group. The ADP that isformed is released, and the protein binding site canonce again bind ATP.

B

Figure 9.2The formation and breakdown of ATP is cyclic.

0221-0224 C9S1 BDOL-829900 8/4/04 4:31 AM Page 223

Understanding Main Ideas1. Identify cellular processes that need energy

from ATP.

2. How does ATP store energy?

3. How can ADP be “recycled” to form ATP again?

4. How do proteins in your cells access the energystored in ATP?

5. List three biological activities that require energy.

Thinking Critically6. Phosphate groups in ATP repel each other because

they have negative charges. What charge mightbe present in the ATP binding site of a protein toattract ATP?

7. Get the Big Picture How does an animal accessthe energy in sunlight? For more help, refer toGet the Big Picture in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

224 ENERGY IN A CELL(t)Dr. K.S. Kim/Peter Arnold, Inc., (b)National Geographic Society Image Collection

Figure 9.3ATP fuels the cellular activitythat drives the organism. DefineOperationally What organelles do these cells or organismsuse for movement?

Some organisms(left) use energyfrom ATP to move.

C

batteries has been used, the batteriescan be taken out, recharged, andreplaced in the holder. In a similarfashion in a cell, when ATP has beenbroken down to ADP, the ADP isreleased from the binding site in theprotein and the binding site may thenbe filled by another ATP molecule.

Uses of Cell EnergyYou can probably think of hun-

dreds of physical activities thatrequire energy, but energy is equallyimportant at the cellular level.

Making new molecules is one waythat cells use energy. Some of thesemolecules are enzymes. Other mole-cules build membranes and cellorganelles. Cells use energy tomaintain homeostasis. Kidneys useenergy to move molecules and ions in order to eliminate waste substances while keeping needed substances in the bloodstream.Figure 9.3 shows several ways thatcells use energy.

List three cellularactivities that require energy.

Stained TEM Magnification: 18 000�

Nerve cells transmitimpulses by usingATP to power theactive transport ofcertain ions.

A

Fireflies and many marine organisms, such asthe jellyfish shown here, produce light by aprocess called bioluminescence. The light resultsfrom a chemical reaction that is powered by thebreakdown of ATP.

B

in.bdol.glencoe.com/self_check_quiz

0221-0224 C9S1 BDOL-829900 8/4/04 4:31 AM Page 224

http://in.bdol.glencoe.com/self_check_quiz

Photosynthesis: Trapping the Sun’s Energy

9.2 PHOTOSYNTHESIS: TRAPPING THE SUN’S ENERGY 225

SECTION PREVIEWObjectivesRelate the structure ofchloroplasts to the events inphotosynthesis.Describe light-dependentreactions.Explain the reactions and products of the light-independent Calvin cycle.

Review Vocabularychloroplast: cell organelle

that captures lightenergy and producesfood to store for lateruse (p. 184)

New Vocabularyphotosynthesislight-dependent reactionslight-independent reactionspigmentchlorophyllelectron transport chainNADP+photolysisCalvin cycle

9.2

Photosynthesis Make the following Foldable to help you illustrate what happens during each phase of photosynthesis.

Fold a vertical sheet of paper in half from top to bottom.

Fold in half from side to side with the fold at the top.

STEP 1 STEP 2

1st PhaseLight-

Dependent

2nd PhaseLight-

Independent

Unfold the paper once. Cut only the fold of the top flap to make two tabs.

Turn the paper vertically and label on the front tabs as shown.

STEP 3 STEP 4

Compare and Contrast As you read Section 9.2, compare and contrast the two phases of photosynthesis under the appropriate tab.

Trapping Energy from SunlightTo use the energy in sunlight, the cells of green organisms must trap light

energy and store it in a manner that is readily usable by cell organelles—inthe chemical bonds of ATP. However, light energy is not available 24 hoursa day, so the cell must also store some of the energy for use during the darkhours. The process that uses the sun’s energy to make simple sugars is calledphotosynthesis. These simple sugars are then converted into complex car-bohydrates, such as starches, which store energy.

Photosynthesis happens in two phases. The light-dependent reactionsconvert light energy into chemical energy. The molecules of ATP produced in the light-dependent reactions are then used to fuel the light-independent reactions that produce simple sugars. The generalequation for photosynthesis is written as follows:

6CO2 � 6H2O → C6H12O6 � 6O2

The BioLab at the end of this chapter can be performed to study whatfactors influence the rate of photosynthesis.

photosynthesisfrom the Greekwords photo,meaning “light,”and syntithenai,meaning “to puttogether”;Photosynthesisputs togethersugar moleculesusing water, car-bon dioxide, andenergy from light.

Standard B.1.3 Know and describe that within the cell are specialized partsfor the transport of materials, energy capture and release, protein building, waste disposal,information feedback, and movement…

Indiana Standards

0225-0230 C9S2 BDOL-829900 8/4/04 4:41 AM Page 225

ExperimentSeparating PigmentsChromatography is an impor-tant diagnostic tool. In thisexperiment, you will use paperchromatography to separatedifferent pigments from plantleaves.

Procedure! Obtain a pre-made plant solution from your teacher.@ Place a few drops 2 cm high on a 5-cm � 14-cm strip of

filter paper. Let it dry. Make sure a small colored spot isvisible.

# Pour rubbing alcohol in a 100-mL beaker to a depth of1 cm.

$ Place the filter paper into the beaker. The filter papershould touch the alcohol, but the dot should not. Hold it in place 15 minutes and observe what happens.

Analysis 1. Explain What did you observe as the solvent moved

up the filter paper?2. Infer Why did you see different colors at different

locations on the filter paper?

(t)Matt Meadows, (b)James Westwater

Figure 9.4The red, yellow, andpurple pigments arevisible in the autumn.Recognize Cause andEffect Why can’t yousee these colors dur-ing the summer?

226 ENERGY IN A CELL

The chloroplast and pigmentsRecall that the chloroplast is the

cell organelle where photosynthesisoccurs. It is in the membranes of thethylakoid discs in chloroplasts that thelight-dependent reactions take place.

To trap the energy in the sun’s light, the thylakoid membranes con-tain pigments, molecules that absorbspecific wavelengths of sunlight. Pig-ments are arranged within the thy-lakoid membranes in clusters known asphotosystems. Although a photosys-tem contains several kinds of pig-ments, the most common ischlorophyll. Chlorophyll absorbsmost wavelengths of light exceptgreen. Because chlorophyll cannotabsorb this wavelength, it is reflected,giving leaves a green appearance. Inthe fall, trees stop producing chloro-phyll in their leaves. Other pigmentsbecome visible, giving leaves like thosein Figure 9.4 a wide variety of colors.The MiniLab on this page will allowyou to separate the pigments in a leaf.Read the Connection to Chemistry at theend of this chapter to find out moreabout biological pigments.

Light-DependentReactions

The first phase of photosynthesisrequires sunlight. As sunlight strikesthe chlorophyll molecules in a photo-system of the thylakoid membrane, theenergy in the light is transferred toelectrons. These highly energized, orexcited, electrons are passed fromchlorophyll to an electron transportchain, a series of proteins embedded inthe thylakoid membrane. Figure 9.5summarizes this process.

Each protein in the chain passesenergized electrons along to the nextprotein, similar to a bucket brigade inwhich a line of people pass a bucket of

0225-0230 C9S2 BDOL-829900 8/4/04 4:42 AM Page 226


water from person to person to fight afire. At each step along the transportchain, the electrons lose energy, just assome of the water might be spilledfrom buckets in the fire-fightingchain. This “lost” energy can be usedto form ATP from ADP, or to pumphydrogen ions into the center of thethylakoid disc.

After the electrons have traveleddown the electron transport chain,they are re-energized in a secondphotosystem and passed down a sec-ond electron transport chain. At thebottom of this chain, the electronsare still very energized. So that thisenergy is not wasted, the electronsare transferred to the stroma of thechloroplast. To do this, an electroncarrier molecule called NADP�

(nicotinamide adenine dinucleotidephosphate) is used. NADP� cancombine with two excited electronsand a hydrogen ion (H�) to becomeNADPH. NADPH does not use theenergy present in the energized elec-trons; it simply stores the energyuntil it can transfer it to the stroma.There, NADPH will play an impor-tant role in the light-independentreactions.

Explain how energyfrom electrons is released.

Restoring electronsRecall that at the beginning of

photosynthesis, electrons are lostfrom chlorophyll molecules whenlight is absorbed. If these electronsare not replaced, the chlorophyll willbe unable to absorb additional lightand the light-dependent reactionswill stop, as will the production ofATP. To replace the lost electrons,molecules of water are split in thefirst photosystem. This reaction iscalled photolysis (fo TAH luh sis).For every water molecule that is

Light-Dependent Reactions

Light energy

Chlorophyllpasses energy

down through theelectron transport chain.

Energized electrons provideenergy that

transfers to chlorophyll.

Sun

splitsH2O

bonds to ADP

formingATPH+

oxygenreleased

for use in thelight-independent reactions.

NADP+

NADPH

P

Figure 9.5Chlorophyll molecules absorb light energyand energize electrons for producing ATPand NADPH.

0225-0230 C9S2 BDOL-829900 8/4/04 4:43 AM Page 227

split, one half molecule of oxygen,two electrons, and two hydrogenions are formed, as shown inFigure 9.6. The oxygen producedby photolysis is released into the airand supplies the oxygen we breathe.The electrons are returned tochlorophyll. The hydrogen ions arepumped into the thylakoid, wherethey accumulate in high concentra-tion. Because this difference in con-centration forms a concentrationgradient across the membrane, H�

ions diffuse out of the thylakoid andprovide energy for the production ofATP. This coupling of the move-ment of H� ions to ATP productionis called chemiosmosis (keh mee ozMOH sis). The MiniLab on this pageshows how the steps of photosynthe-sis were traced.

Light-IndependentReactions

The second phase of photosynthe-sis does not require light. It is calledthe Calvin cycle, which is a series ofreactions that use carbon dioxide toform sugars. The Calvin cycle takesplace in the stroma of the chloroplast,as shown in Figure 9.7.


Sun

Chlorophyll O2 + 2H+

H2O

2e–

H2O 2H+ + O2 + 2e– 1

2

1

2

Figure 9.6In photolysis, a molecule of water is split toreplace electrons lost from chlorophyll, H+

for chemiosmosis, and oxygen. Infer Howmany molecules of water must be splitto make a molecule of oxygen gas?

Formulate ModelsUse Isotopes to UnderstandPhotosynthesis C. B. van Nieldemonstrated that photosynthesis is a light-dependent reaction inwhich the O2 comes from water.Other scientists confirmed his find-ings by using radioactive isotopes ofoxygen as tracers. Radioactive tracersare used to follow a particular moleculethrough a chemical reaction.

Procedure! Study the following general equation that resulted from

the van Niel experiment:CO2 � 2H2O* → CH2O � H2O � O2*

@ Radioactive water, water tagged with an isotope of oxygenas a tracer (shown by the *), was used. Note where thetagged oxygen ends up on the right side of the equation.

# Assume that the experiment was repeated, but this time aradioactive tag was put on the oxygen in CO2.

$ Using materials provided by your teacher, model what youpredict the appearance of the results would be. Yourmodel must include a “tag” to indicate the oxygen isotopeon the left side of the arrow as well as where it ends upon the right side of the arrow.

% You also must use labels or different colors in your modelto indicate what happens to the carbon and hydrogen.

Analysis1. Explain How can an isotope be used as a tag?2. Use Models Using your model, predict what happens to:

a. all oxygen molecules that originated from carbon dioxide.b. all carbon molecules that originated from carbon dioxide.c. all hydrogen molecules that originated from water.

van Niel

0225-0230 C9S2 BDOL-829900 8/4/04 4:43 AM Page 228


C C C C C

C

C C C C C C

C C C

C C C

C C CC C C

C C C

C C C C C C

C C C

(Sugars and other carbohydrates)

ADP +

ADP + ATP

ATP

NADP+

NADPH

(RuBP)

(CO2)

(Unstable intermediate)

(PGAL)(PGAL)

(PGAL)

CalvinCycle

P

P

Formation of 3-carbon moleculesThe six-carbon sugarformed in Step Aimmediately splits to form two three-carbonmolecules.

BB

Use of ATP andNADPH A series of reactions involving ATP and NADPH from the light-dependent reactionsconverts the three-carbonmolecules into phospho-glyceraldehyde (PGAL),three-carbon sugars withhigher energy bonds.

CC

Sugar production One outof every six molecules of PGALis transferred to the cytoplasmand used in the synthesis ofsugars and other carbohydrates.After three rounds of the cycle,six molecules of PGAL areproduced.

DD

RuBP is replenishedFive molecules of PGAL,each with three carbonatoms, produce threemolecules of the five-carbon RuBP. Thisreplenishes the RuBP thatwas used up, and the cyclecan continue.

EE

Carbon fixationThe carbon atom from CO2bonds with a five-carbonsugar called ribulosebiphosphate (RuBP) toform an unstable six-carbon sugar.

AA

The stroma in chloroplastshosts the Calvin cycle.

Color-enhanced TEMMagnification: 6300�

The Calvin CycleFigure 9.7The Calvin cycle takes the carbon in CO2, adds it to one mole-cule of RuBP, and forms sugars through a series of reactionsin the stroma of chloroplasts. The NADPH and ATP producedduring the earlier light-dependent reactions are importantmolecules for this series of reactions. Critical Thinking Whyis the Calvin cycle in plants directly and indirectlyimportant to animals?

0225-0230 C9S2 BDOL-829900 8/4/04 4:43 AM Page 229

Understanding Main Ideas1. Why do you see green when you look at a leaf on

a tree? Why do you see other colors in the fall?

2. How do the light-dependent reactions of photosynthesis relate to the Calvin cycle?

3. What is the function of water in photosynthesis?Explain the reaction that achieves this function.

4. How does the electron transport chain transferlight energy in photosynthesis?

Thinking Critically5. In photosynthesis, is chlorophyll considered a reac-

tant, a product, or neither? How does the role ofchlorophyll compare with the roles of CO2 and H2O?

6. Get the Big Picture Identify the parts of thechloroplast in which the various steps of photo-synthesis take place. For more help, refer to Getthe Big Picture in the Skill Handbook.


230 ENERGY IN A CELLCORBIS/Bettmann-UPI

The Calvin cycleThe Calvin cycle, named after

Melvin Calvin, who worked out thedetails of the reactions, is called a cyclebecause one of the last moleculesformed in the series of chemical reac-tions is also one of the moleculesneeded for the first reaction of thecycle. Therefore, one of the productscan be used again to continue the cycle.

You have learned that in the elec-tron transport chain, an energizedelectron is passed from protein toprotein, and the energy is releasedslowly. You can imagine that making acomplex carbohydrate from a mole-cule of CO2 would be a large task fora cell, so the light-independent reac-tions in the stroma of the chloroplastbreak down the complicated processinto small steps.

At the beginning of the Calvincycle, one molecule of carbon diox-ide is added to one molecule ofRuBP to form a six-carbon sugar.This step is called carbon fixationbecause carbon is “fixed” into a six-carbon sugar. In a series of reactions,the sugar breaks down and is eventu-ally converted to two three-carbonsugars called phosphoglyceralde-hyde, or PGAL. After three roundsof the cycle, with each round fixingone molecule of CO2, six moleculesof PGAL are produced. Five of thesemolecules are rearranged to formthree molecules of RuBP, the start-ing material. The sixth molecule ofPGAL is available to the organismfor making sugars, complex carbo-hydrates, and other organic com-pounds. As you will see in the nextsection, PGAL is important to allorganisms because it plays a role incellular respiration.

Biochemist

I f you are curious about whatmakes plants and animals grow

and develop, consider a career as abiochemist. The basic research ofbiochemists seeks to understandhow processes in an organism workto ensure the organism’s survival.

Skills for the JobA bachelor’s degree in chemistry or

biochemistry will qualify you to be a lab assistant. For a more involved position, you will need a master’s degree; advanced research requires a Ph.D. Somebiochemists work with genes to create new plants and newchemicals from plants. Others research the causes and curesof diseases or the effects of poor nutrition. Still othersinvestigate solutions for urgent problems, such as findingbetter ways of growing, storing, and caring for crops.

To find out more about careers in related fields,visit in.bdol.glencoe.com/careers


0225-0230 C9S2 BDOL-829900 8/4/04 4:44 AM Page 230

http://in.bdol.glencoe.com/careers


9.3SECTION PREVIEWObjectivesCompare and contrastcellular respiration andfermentation.Explain how cells obtainenergy from cellular respiration.

Review Vocabularymitochondria: cell organ-

elles that transformenergy for the cell (p. 185)

New Vocabularycellular respirationanaerobicaerobicglycolysiscitric acid cyclelactic acid fermentationalcoholic fermentation

anaerobic fromthe Greek wordsan, meaning“without,” andaeros, meaning“air”; Anaerobicorganisms can livewithout oxygen.

9.3 GETTING ENERGY TO MAKE ATP 231

What happens to sugars?Using Prior Knowledge Youknow that the chlorophyll ingreen plants is the key to photo-synthesis and that sugars are pro-duced. You also know that yourbody needs energy to survive.Sugars can be broken down incells to yield large amounts ofenergy. But, your cells can’t con-vert light energy to sugars. Whatwill you do? Fortunately, the cellsof all organisms can use the sug-ars made by plants during theCalvin cycle. By eating plantmaterial, animals, too, can accessthe sun’s energy.Identify In which organelle are sugars converted to ATP?

Getting Energy to Make ATP

Michael Keller/CORBIS

Cellular RespirationThe process by which mitochondria break down food molecules to pro-

duce ATP is called cellular respiration. There are three stages of cellularrespiration: glycolysis, the citric acid cycle, and the electron transport chain.The first stage, glycolysis, is anaerobic—no oxygen is required. The lasttwo stages are aerobic and require oxygen to be completed.

GlycolysisGlycolysis (gli KAH lih sis) is a series of chemical reactions in the cyto-

plasm of a cell that break down glucose, a six-carbon compound, into twomolecules of pyruvic (pie RUE vik) acid, a three-carbon compound.Because two molecules of ATP are used to start glycolysis, and only fourATP molecules are produced, glycolysis is not very effective, producingonly two ATP molecules for each glucose molecule broken down.

In the electron transport chain of photosynthesis, an electron carriercalled NADP� was described as carrying energized electrons toanother location in the cell for further chemical reactions. Glycolysisalso uses an electron carrier, called NAD� (nicotinamide adenine di-nucleotide). NAD� forms NADH when it accepts two electrons.

Standard B.1.3 Know and describe that within the cell are specialized parts forthe transport of materials, energy capture and release, protein building, waste disposal, informationfeedback, and movement…

Indiana Standards

0231-0243 C9S3 BDOL-829900 8/4/04 4:59 AM Page 231

Notice in Figure 9.8 that twomolecules of PGAL are formed dur-ing glycolysis. Recall that PGALalso forms in the Calvin cycle. ThePGAL made during photosynthesiscan enter the glycolysis pathway andlead to the formation of ATP andorganic molecules.

Following glycolysis, the pyruvicacid molecules move into the mito-chondria, the organelles that transformenergy for the cell. In the presence ofoxygen, two more stages complete cel-lular respiration: the citric acid cycleand the electron transport chain of themitochondrion. Before these twostages can begin, however, pyruvic acidundergoes a series of reactions in whichit gives off a molecule of CO2 and com-bines with a molecule called coenzymeA to form acetyl-CoA. The reactionwith coenzyme A produces a molecule

of NADH and H�. These reactionsare shown in Figure 9.9.

The citric acid cycleThe citric acid cycle, also called

the Krebs cycle, is a series of chemicalreactions similar to the Calvin cyclein that the molecule used in the firstreaction is also one of the end prod-ucts. Read Figure 9.10 to study thecitric acid cycle.

For every turn of the cycle, one mol-ecule of ATP and two molecules of car-bon dioxide are produced. Twoelectron carriers are used, NAD� andFAD (flavin adenine dinucleotide). Atotal of three NADH, three H� ions,and one FADH2 are formed. The elec-tron carriers each pass two energizedelectrons along to the electron trans-port chain in the inner membrane ofthe mitochondrion.


C C C CC C C P

C C C

C C C

C C CPC C

ENERGY ENERGY

2ATP2ADP

4ADP + 4 P

2NAD+2PGAL

Glucose

4ATP

2NADH + 2H+

2 Pyruvicacid

C C C C C C C C C CC

NAD+

CO2

NADH + H+

Pyruvicacid

Outside themitochondrion

Mitochondrialmembrane

Coenzyme A

Pyruvicacid

Inside themitochondrion

Intermediateby-product

- CoAAcetyl-CoA

+

Figure 9.8Glycolysis breaks downa molecule of glucoseinto two molecules ofpyruvic acid. In theprocess, it forms a netof two molecules ofATP, two molecules ofNADH , and two hydro-gen ions.

Figure 9.9Before the citric acidcycle and electron trans-port chain begin, pyruvicacid undergoes a seriesof reactions. InferWhat products areformed as a result ofthe reactions withinthe mitochondrion?

0231-0243 C9S3 BDOL-829900 8/4/04 5:00 AM Page 232

The Citric Acid CycleFigure 9.10The citric acid cycle breaks down a molecule ofacetyl-CoA and forms ATP and CO2. The electroncarriers NAD� and FAD pick up energized electronsand pass them to the electron transport chain inthe inner mitochondrial membrane. Critical ThinkingHow many CO2 molecules are produced for everyglucose molecule that entered the cellular respira-tion pathways?


P

NAD+

NAD+

NAD+

FADH2FAD

C C

NADH + H+

NADH + H+

ATP

ADP +

(Acetyl-CoA)

(Oxaloacetic acid)(Citric acid)

CitricAcidCycle

O O(CO2)

O O(CO2)

NADH + H+

C C C C

C C C C

C C C C

C C C C

C C C C C

C

C C C C C

C

C

Formation of the second CO2 Anothermolecule of CO2 is released, forming a four-carboncompound. One molecule of ATP and a moleculeof NADH are also produced.

CC

Citric acid The two-carboncompound acetyl-CoA reactswith a four-carbon compoundcalled oxaloacetic acid to formcitric acid, a six-carbonmolecule.

AA Formation of CO2 A moleculeof CO2 is formed, reducing theeventual product to a five-carboncompound. In the process, amolecule of NADH and H+ isproduced.

BB

Profs. P. Motta & T. Naguro/Science Photo Library/Custom Medical Stock Photo

Recycling of oxaloacetic acid The four-carbon molecule goesthrough a series of reactions in which FADH2, NADH, and H+

are formed. The carbon chainis rearranged, and oxaloaceticacid is again made availablefor the cycle.

DD

The mitochondria hostthe citric acid cycle.

Magnification: unavailable

0231-0243 C9S3 BDOL-829900 8/4/04 5:00 AM Page 233

The electron transport chainThe electron transport chain in

the inner membrane of the mito-chondrion is very similar to the elec-tron transport chains of thethylakoid membrane in the chloro-plasts of plant cells during photo-synthesis. NADH and FADH2deliver energized electrons at thetop of the chain. The electrons arepassed from protein to proteinwithin the membrane, slowly releas-ing their energy in steps. Some ofthat energy is used directly to formATP; some is used by an enzyme topump H� ions into the center of themitochondrion. Consequently, themitochondrion inner membranebecomes positively charged becauseof the high concentration of posi-tively charged hydrogen ions. At thesame time, the exterior of the mem-brane is negatively charged, whichfurther attracts hydrogen ions. Thegradient of H� ions that resultsacross the inner membrane of themitochondrion provides the energy

for ATP production, just as it does in the chemiosmotic process that takes place at the thylakoid mem-branes in the chloroplasts. Figure 9.11summarizes the electron transportchain and the formation of ATP.

The final electron acceptor at thebottom of the chain is oxygen, whichreacts with four hydrogen ions (4H�)and four electrons to form two mole-cules of water (H2O). This is why oxy-gen is so important to our bodies.Without oxygen, the proteins in theelectron transport chain cannot passalong the electrons. If a protein cannotpass along an electron to oxygen, itcannot accept another electron. Veryquickly, the entire chain becomesblocked and ATP production stops.

Overall, the electron transportchain adds 32 ATP molecules to thefour already produced. Obviously,the aerobic process of ATP produc-tion is very effective. In the absenceof oxygen, however, an anaerobicprocess can produce small amountsof ATP to keep the cell from dying.


H� H�

H�

H�

H�

H�

�

�

P

Electroncarrier proteins

Electronpathway

Space betweeninner and outer

membranes

Enzyme

ADP � ATP

Innermembrane

Center ofmitochondrion

NAD�

FAD

NADH

FADH2

4 H� � O2� 4 electrons

H2O

H2O

e�

Figure 9.11In the electron transportchain, the carrier mole-cules NADH and FADH2give up electrons thatpass through a series ofreactions. Oxygen is thefinal electron acceptor.

0231-0243 C9S3 BDOL-829900 8/4/04 5:01 AM Page 234


FermentationThere are times, such as during

heavy exercise, when your cells arewithout oxygen for a short period oftime. When this happens, an anaero-bic process called fermentation fol-lows glycolysis and provides a meansto continue producing ATP until oxy-gen is available again. There are twomajor types of fermentation: lacticacid fermentation and alcoholic fer-mentation. The table in Figure 9.12compares the two processes with res-piration. Perform the Problem-SolvingLab shown here to further compareand contrast cellular respiration andfermentation.

Infer when yourbody might perform fermentationreactions.

Lactic acid fermentationYou know that under anaerobic con-

ditions, the electron transport chainbacks up because oxygen is not present

Gerard Vandystadt/Vandystadt Agency/Photo Researchers

Figure 9.12Lactic acid and alcoholic fermentations are comparablein the production of ATP, but compared to cellular respi-ration, it is obvious that fermentation is far less efficientin ATP production. This runner’s muscles have beendepleted of oxygen and fermentation is taking place.

Comparison of Fermentation to Cellular Respiration

Lactic Acid Alcoholic Cellular respiration

glucose glucose glucose

glycolysis (pyruvic acid) glycolysis (pyruvic acid) glycolysis (pyruvic acid)

carbon dioxide carbon dioxide

� �

lactic acid alcohol water

� � �

2 ATP 2 ATP 36 ATP

Acquire InformationCellular respiration or fermentation? The methods bywhich organisms derive ATP may differ; however, the result,the production of ATP molecules, is similar.

Solve the ProblemStudy the table in Figure 9.12 and evaluate cellular respiration,lactic acid fermentation, and alcoholic fermentation.

Thinking Critically1. Describe Why does cellular respiration produce so much

more ATP than does fermentation?2. Use Scientific Explanations Describe a situation when a

human would need to use more than one of the processeslisted above.

3. Analyze Think of an organism that might generate ATPonly by fermentation and consider why fermentation is thebest process for the organism.

0231-0243 C9S3 BDOL-829900 8/4/04 5:01 AM Page 235

as the final electron acceptor. AsNADH and FADH2 arrive at the chainfrom the citric acid cycle and glycolysis,they cannot release their energizedelectrons. The citric acid cycle and gly-colysis cannot continue without asteady supply of NAD� and FAD.

The cell does not have a method toreplace FAD during anaerobic condi-tions; however, NAD� can bereplaced through lactic acid fermenta-tion. Lactic acid fermentation is oneof the processes that supplies energywhen oxygen is scarce. Two moleculesof pyruvic acid produced in glycolysisuse NADH to form two molecules oflactic acid. This releases NAD� to beused in glycolysis, allowing two ATPmolecules to be formed for each glu-cose molecule. The lactic acid is trans-ferred from muscle cells, where it isproduced during strenuous exercise,to the liver that converts it back topyruvic acid. The lactic acid thatbuilds up in muscle cells results inmuscle fatigue.

Alcoholic fermentationAnother type of fermentation,

alcoholic fermentation, is used by yeast cells and some bacteria toproduce CO2 and ethyl alcohol.When making bread, like that shownin Figure 9.13, yeast cells produceCO2 that forms bubbles in the dough.Eventually the heat of the oven killsthe yeast and the bubble pockets areleft to lighten the bread. You can dothe MiniLab on this page to studyalcoholic fermentation in apple juice.


Figure 9.13Alcoholic fermentation by the yeast in breaddough produces CO2 bubbles that raise thedough. Think Critically What happens tothe CO2?

PredictDetermine if Apple Juice Ferments Some organ-isms, such as yeast, can breakdown food molecules and syn-thesize ATP when no oxygen isavailable. When food is avail-able, yeast carry out alcoholicfermentation, producing CO2.Thus, the production of CO2 inthe absence of oxygen can beused to judge whether alcoholicfermentation is taking place.

Procedure! Carefully study the diagram

and set up the experimentas shown.

@ Hold the test tube in abeaker of warm (not hot)water and observe.

Analysis1. Interpret Data What were the gas bubbles that came

from the plastic pipette?2. Hypothesize What would happen to the rate of bubbles

given off if more yeast were present in the mixture?3. Analyze Why was the test tube placed in warm water?4. Draw Conclusions Was the process you demonstrated

aerobic or anaerobic? Explain.

Yeast andapple juice

Plastic pipette

Water

Test tube

Metalwashers

Matt Meadows

0231-0243 C9S3 BDOL-829900 8/4/04 5:02 AM Page 236

ComparingPhotosynthesis andCellular Respiration

The production and breakdownof food molecules are accomplishedby distinct processes that bear cer-tain similarities. Both photosynthe-sis and cellular respiration useelectron carriers and a cycle ofchemical reactions to form ATP.Both use electron transport chainsto form ATP and to create a chemi-cal and a concentration gradient ofH� within a cell. This hydrogen iongradient can be used to form ATP bychemiosmosis.

However, despite using such simi-lar tools, the two cellular processesaccomplish quite different tasks.Photosynthesis produces high-energycarbohydrates and oxygen from thesun’s energy, whereas cellular respira-tion uses oxygen to break down car-bohydrates to form ATP andcompounds that provide less energy.Also, one of the end products of cel-lular respiration is CO2, which is oneof the beginning products for photo-synthesis. The oxygen produced dur-ing photosynthesis is a criticalmolecule necessary for cellular respi-ration. Table 9.1 compares thesecomplementary processes.

Understanding Main Ideas1. Compare the ATP yields of glycolysis, the citric

acid cycle, and the electron transport chain.2. How do alcoholic fermentation and lactic acid fer-

mentation differ?3. How is most of the ATP from aerobic respiration

produced?4. Why is lactic acid fermentation important to the

cell when oxygen is scarce?5. How many ATP molecules are produced after the

electrons go down the electron transport chain?

Thinking Critically6. Compare the energy-producing processes in a

jogger’s leg muscles with those of a sprinter’sleg muscles. Which is likely to build up more lactic acid? Explain.

7. Get the Big Picture How are the chemical reac-tions of photosynthesis and cellular respirationconnected? What is the significance of this con-nection? For more help, refer to Get the BigPicture in the Skill Handbook.


9.3 GETTING ENERGY TO MAKE ATP 237(l)file photo, (r)George Robbins

Table 9.1 Comparison of Photosynthesis and Cellular Respiration

Photosynthesis Cellular Respiration

Food synthesized Food broken down

Energy from sun stored in glucose Energy of glucose released

Carbon dioxide taken in Carbon dioxide given off

Oxygen given off Oxygen taken inProduces sugars Produces CO2from PGAL and H2ORequires Does notlight require lightOccurs only in Occurs in allpresence of living cellschlorophyll


0231-0243 C9S3 BDOL-829900 8/4/04 5:02 AM Page 237


What factors influence photosynthesis?

ProblemHow do different wavelengths of light that a plant receivesaffect its rate of photosynthesis?

ObjectivesIn this BioLab, you will:■ Observe photosynthesis in an aquatic organism.■ Measure the rate of photosynthesis.■ Research the wavelengths of various colors of light.■ Observe how various wavelengths of light influence the

rate of photosynthesis.■ Use the Internet to collect and compare data from other

students.

Materials1000-mL beaker lamp with reflector andthree Elodea plants 150-watt bulbstring 0.25% sodium hydrogenwashers carbonate (baking soda) colored cellophane, solution

assorted colors watch with second hand

Safety PrecautionsCAUTION: Always wear goggles in the lab.

Skill HandbookIf you need help with this lab, refer to the Skill Handbook.

1. Construct a basic setup like the one shown here.2. Create a data table to record your measurements. Be sure

to include a column for each color of light you will inves-tigate and a column for the control.

3. Place the Elodea plants in the beaker, thencompletely cover them with water. Addsome of the baking soda solution. The solu-tion provides CO2 for the aquarium plants.Be sure to use the same amount of waterand solution for each trial.

PROCEDUREPROCEDURE

PREPARATIONPREPARATIONBefore YouBegin

Oxygen is one of the prod-ucts of photosynthesis.Because oxygen is onlyslightly soluble in water,aquatic plants such asElodea give off visiblebubbles of oxygen as theycarry out photosynthesis. By measuring the rate atwhich bubbles form, youcan measure the rate ofphotosynthesis.

Matt Meadows

0231-0243 C9S3 BDOL-829900 8/4/04 5:04 AM Page 238

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE


1. Interpret Observations From wheredid the bubbles of oxygen emerge?

2. Make Inferences Explain how counting bubbles measures the rate of photosynthesis.

3. Use the Internet Look up the wave-lengths of the colors of light you used.Make a graph of your data and dataposted by other students with the rateof photosynthesis per minute plottedagainst the wavelengths of light youtested for both the control and experi-mental setups. Write a sentence or twoexplaining the graph.

4. Why was it important to use the same amount of sodiumhydrogen carbonate in each trial?ERROR ANALYSIS

4. Conduct a control by directing the lamp (without col-ored cellophane) on the plant and noticing when you seethe bubbles.

5. Observe and record the number of oxygen bubbles thatElodea generates in five minutes.

6. Cover the lamp with a piece of colored cellophane andrepeat steps 4 and 5.

7. Repeat steps 4 and 5 with a different color of cellophane.8. Go to to post

your data.9. Return plant material to an

aquarium to prevent it from drying out.CLEANUP AND DISPOSAL

Bubbles observed in five minutes

Color 1 Color 2Control

Data Table

Find this BioLab using the link below and postyour data in the data table provided for thisactivity. Using the additional data from otherstudents on the Internet, analyze the com-bined data and expand your graph.

in.bdol.glencoe.com/internet_lab

in.bdol.glencoe.com/internet_lab

Runk-Schoenberger/Grant Heilman Photography

0231-0243 C9S3 BDOL-829900 8/4/04 5:08 AM Page 239

http://in.bdol.glencoe.com/internet_lab

http://in.bdol.glencoe.com/internet_lab


Plant Pigments

In photosynthesis, light energy is converted intochemical energy. To begin the process, light is

absorbed by colorful pigment molecules containedin chloroplasts.

A pigment is a substance that can absorb spe-cific wavelengths of visible light. You can observethe colors of the various wavelengths of light byletting sunlight pass through a prism to create a“rainbow,” or spectrum, that has red light on oneend, violet on the other, and orange, yellow,green, blue, and indigo light in between.

Every photosynthetic pigment is distinctive inthat it absorbs specific wavelengths in the visiblelight spectrum.

Chlorophylls a and b The principal pig-ment of photosynthesis is chlorophyll.Chlorophyll exists in two forms, designated as aand b. Chlorophyll a and b both absorb light inthe violet to blue and the red to red-orange partsof the spectrum, although at somewhat differentwavelengths. These pigments also reflect greenlight, which is why plant leaves appear green.

When chlorophyll b absorbs light, it transfersthe energy it acquires to chlorophyll a, which thenfeeds that energy into the chemical reactions thatlead to the production of ATP and NADPH. Inthis way, chlorophyll b acts as an “accessory” pig-ment by making it possible for photosynthesis tooccur over a broader spectrum of light than wouldbe possible with chlorophyll a alone.

Carotenoids and phycobilins Carotenoidsand phycobilins are other kinds of accessory pig-ments that absorb wavelengths of light differentfrom those absorbed by chlorophyll a and b, andso extend the range of light that can be used forphotosynthesis.

Carotenoids are yellow-orange pigments.They are found in all green plants, but theircolor is usually masked by chlorophyll.

Carotenoids are also found in cyanobacteria andin brown algae. A particular carotenoid calledfucoxanthin gives brown algae their characteris-tic dark brown or olive green color.

Phycobilins are blue and red. Red algae gettheir distinctive blood-red coloration from phy-cobilins. Some phycobilins can absorb wave-lengths of green, violet, and blue light, whichpenetrate deep water. One species of red algaethat contains these pigments is able to live atocean depths of 269 meters (882.5 feet). Thealgae’s pigments absorb enough of the incrediblyfaint light that penetrates to this depth—only atiny percent of what is available at the water’ssurface—to power photosynthesis.

Think Critically How do you think accessorypigments may have influenced the spread of pho-tosynthetic organisms into diverse habitats such asthe deep sea?

To find out more about pigments, visit in.bdol.glencoe.com/chemistry

(t)Robert Calentine/Visuals Unlimited, (inset)Dan Gotshall/Visuals Unlimited

Pigments color cyanobacteria(above) and red algae (inset).

LM Magnification: 450�

0231-0243 C9S3 BDOL-829900 8/4/04 5:11 AM Page 240

http://in.bdol.glencoe.com/chemistry

Section 9.1Vocabulary(ADP) adenosine

diphosphate (p. 222)(ATP) adenosine

triphosphate (p. 222)

VocabularyCalvin cycle (p. 228)chlorophyll (p. 226)electron transport chain

(p. 226)light-dependent

reactions (p. 225)light-independent

reactions (p. 225)NADP� (p. 227)photolysis (p. 227)photosynthesis (p. 225)pigment (p. 226)

Photosynthesis:Trapping theSun’s Energy

Getting Energyto Make ATP

STUDY GUIDESTUDY GUIDE

CHAPTER 9 ASSESSMENT 241

To help you review photo-synthesis and cellular respiration, use theOrganizational Study Fold on page 225.

(t)Tom McHugh/Photo Researchers, (b)Matt Meadows

The Need forEnergy

Section 9.2

Section 9.3 Vocabularyaerobic (p. 231)alcoholic fermentation

(p. 236)anaerobic (p. 231)cellular respiration

(p. 231)citric acid cycle (p. 232)glycolysis (p. 231)lactic acid fermentation

(p. 236)

Key Concepts■ ATP is the molecule that stores energy for

easy use within the cell.■ ATP is formed when a phosphate group is

added to ADP. When ATP is brokendown, ADP and phosphate are formed andenergy is released.

■ Green organisms trap the energy in sun-light and store it in the bonds of certainmolecules for later use.

■ Organisms that cannot use sunlight directlyobtain energy by consuming plants or otherorganisms that have consumed plants.

Key Concepts■ Photosynthesis is the process by which cells

use light energy to make simple sugars. ■ Chlorophyll in the chloroplasts of plant

cells traps light energy needed for photosynthesis.

■ The light reactions of photosynthesis pro-duce ATP and result in the splitting ofwater molecules.

■ The reactions of the Calvin cycle makecarbohydrates using CO2 along with ATPand NADPH from the light reactions.

Key Concepts■ In cellular respiration, cells break down

carbohydrates to release energy. ■ The first stage of cellular respiration, gly-

colysis, takes place in the cytoplasm anddoes not require oxygen.

■ The citric acid cycle takes place in mito-chondria and requires oxygen.

in.bdol.glencoe.com/vocabulary_puzzlemaker

0231-0243 C9S3 BDOL-829900 8/4/04 5:11 AM Page 241

http://in.bdol.glencoe.com/vocabulary_puzzlemaker

242 CHAPTER 9 ASSESSMENT

Review the Chapter 9 vocabulary words listed inthe Study Guide on page 241. For each set ofvocabulary words, choose the one that does notbelong. Explain why it does not belong.

1. light-dependent reactions—Calvin cycle—chlorophyll

2. glycolysis—alcoholic fermentation—aerobic3. NADP�—chlorophyll—pigment4. photolysis—Calvin cycle—light-dependent

reactions5. cellular respiration—citric acid cycle—

photosynthesis

6. Which of the following is a product of theCalvin cycle?A. carbon dioxideB. NADP�

C. oxygenD. FADH2

7. ________ processes require oxygen, whereas________ processes do not.A. Anaerobic—aerobicB. Aerobic—anaerobicC. Photolysis—aerobicD. Aerobic—respiration

8. Four molecules of glucose would give a netyield of ________ ATP following glycolysis.A. 8 C. 4B. 16 D. 12

9. In which of the following structures do thelight-independent reactions of photosynthesistake place?A. C.

B. D.

10. What is the first process in an animal cell tobe affected by anaerobic conditions?A. citric acid cycleB. fermentationC. glycolysisD. electron transport chain

11. In which stage of cellular respiration is glucose broken down into two molecules of pyruvic acid?A. Calvin cycleB. glycolysisC. citric acid cycle D. electron transport chain

12. Which of the following is a similarity betweenthe citric acid cycle and the Calvin cycle?A. Both cycles utilize oxygen.B. Both cycles produce carbon dioxide.C. Both cycles utilize ATP to break down

carbon bonds.D. Both cycles recycle the molecule needed

for the first reaction.13. When yeast ferments the sugar in a bread

mixture, what is produced that causes thebread dough to rise?A. carbon dioxide C. ethyl alcoholB. water D. oxygen

14. Open Ended Why would human musclecells contain many more mitochondria thanskin cells?

15. Open Ended How are cellular respirationand photosynthesis complementaryprocesses?

16. Open Ended What happens to sunlight that strikes a leaf but is not trapped bychlorophyll?

17. Sequence Describe the pathway of elec-trons from the time they enter the inter-membrane space of the mitochondrion tothe time they are returned to the inside ofthe mitochondrion.

in.bdol.glencoe.com/chapter_test

0231-0243 C9S3 BDOL-829900 8/4/04 5:12 AM Page 242

http://in.bdol.glencoe.com/chapter_test

CHAPTER 9 ASSESSMENT 243

18. Concept Map Make a concept map usingthe following vocabulary terms: cellular res-piration, glycolysis, citric acid cycle, electrontransport chain.

19. Muscle tissueis made of different types of fibers—fast-twitchand slow-twitch. These fibers vary in meta-bolic activities. Visit to find out about the various types of musclefibers. How do the metabolic activities ofthese fibers vary? What types of fibers areused for different movements and why?

REAL WORLD BIOCHALLENGE

are the steps of

2.

4.

1. 3.

which takes place in mitochondria

Multiple ChoiceStudy the table and answer questions20–23.

The following experimental data wascollected by placing equal amounts ofvarious plant parts in sealed containersand exposing them to various light col-ors. After eight hours in the container,the increase in oxygen was measured in the container.

Rate of PhotosynthesisContainer Plant Plant Part Light Color Temperature Increase

(°C) in O2 (mL)

1 Geranium Leaf Red 22 120

2 Geranium Leaf Green 22 15

3 Geranium Root Red 22 0

4 Violet Leaf Red 22 80

5 Violet Leaf Green 22 10

in.bdol.glencoe.com

20. One could compare the amount of oxygenproduced in eight hours at two differentlight colors by comparing _________.A. 1 and 3 C. 1 and 5B. 2 and 4 D. 1 and 2

21. In which container was photosynthesis tak-ing place at the fastest rate?A. 1 C. 3B. 2 D. 4

22. In which container was photosynthesis notoccurring?A. 1 C. 3B. 2 D. 4

23. According to the data, which variable determined whether or not photosynthesisoccurred?A. plant C. temperatureB. light color D. plant part

Constructed Response/Grid InRecord your answers on your answer document.

24. Open Ended Compare the energy storage in photosynthesis to the energy storage in cellular respiration.

25. Open Ended Compare alcoholic fermentation and lactic acid fermentation in terms of startingand ending material and ATP production.

B.1.9

B.1.9

in.bdol.glencoe.com/standardized_test

The assessed Indiana standard appears next to the question.

0231-0243 C9S3 BDOL-829900 8/4/04 5:13 AM 3

http://in.bdol.glencoe.com

http://in.bdol.glencoe.com/standardized_test

The Chemistry of LifeAlthough you are studying biology, chemistry is

fundamental to all biological functions. Under-standing some of the basic concepts of chemistrywill enhance your understanding of the biologicalworld.

Elements and AtomsEvery substance in and on Earth is composed

of one or more kinds of elements. An atom, thesmallest component of an element, is made ofeven smaller particles called electrons, protons,and neutrons. Atoms react to form compounds.

The Life of a CellAll organisms are made of cells, and each cell

is like a complex, self-contained machine thatcan perform life functions. Yet as small as they are,all of the mechanisms and processes of these littlemachines are not fully known, and scientistscontinue to unravel the marvelous mysteries of the living cell.

The Cell Theory

Van Leeuwenhoek might haveviewed microorganisms likethese found in a droplet ofpond water.

LM Magnification: 100�

Carbon IsotopesIsotopes of carbon contain different numbersof neutrons.Carbon-12: six protons and six neutronsCarbon-13: six protons and seven neutronsCarbon-14: six protons and eight neutrons

Cells are microscopic machines.

244

In the 1600s, Anton van Leeuwenhoek was the first personto view living organisms through a microscope. Another sci-

entist, Robert Hooke, named the structures cells. Two hundredyears later, several scientists, including Matthias Schleiden,Theodor Schwann, and Rudolf Virchow continued to studyanimal and plant tissues under the microscope. Conclusionsfrom many scientists were combined to form the cell theory:

1. All organisms are composed of one or more cells.2. The cell is the basic unit of organization of organisms.3. All cells come from preexisting cells.

(t)Michael Rosenfelf/Tony Stone Images, (b)Science VU/Visuals Unlimited

0244-0249 U3 BD/Rev BDOL-829900 8/4/04 1:44 PM Page 244

r-phosphate bone

rogen bonds betweengenous bases

A

A

A

P

P

P

P

D

D

D

D

D

D

D

DT

T

T

G

G

C

C

Substrate

Activesite

The Life of a Cell

Color-enhanced TEM Magnification: 41 150�

An enzyme has an area called anactive site in which a specific sub-strate undergoes a chemical reaction.

Color-enhanced TEMMagnification: 4800�

Nucleic acids are made of subunits called nucleo-tides. Each one consists of a sugar, a phosphate group,and a nitrogenous base.

Organelles

THE LIFE OF A CELL 245

A prokaryotic cell does notcontain membrane-boundorganelles.

Organic CompoundsCarbohydrates are chemical compounds made

of carbon, hydrogen, and oxygen. Common carbo-hydrates include sugars, starches, and cellulose.Lipids, known as fats and oils, contain a glycerolbackbone and three fatty acid chains. Proteins arelarge molecules made of amino acids connected bypeptide bonds. Enzymes are proteins that changethe rates of chemical reactions. Nucleic acids suchas DNA and RNA are complex biomolecules thatstore cellular information in the form of a code.

Eukaryotes and Prokaryotes All cells are surrounded by a plasma membrane.

Eukaryotic cells contain membrane-bound organelleswithin the cell. Cells without internal membrane-bound organelles are called prokaryotic cells.

A eukaryotic cell con-tains membrane-bound organelles.

(t)Dr. Kari Lounatmaa/Science Photo Library/Photo Researchers, (b)Moredun Animal Health, Ltd./Science Photo Library/Photo Researchers


246 BIODIGEST UNIT 3 REVIEW

Carbohydrate

Phospholipidbilayer

ProteinFatty acid tail

Phosphate head

The plasma membrane is composed ofa lipid bilayer with embedded proteins.

Plasma membrane

Mitochondrion

Nucleus

Chloroplast

Cell wall

Vacuole

Golgi apparatus

Ribosomes

Roughendoplasmic

reticulum

Plant cell Animal cell

The Life of a Cell

Color-enhanced TEM Magnification: unavailable Color-enhanced TEM Magnification: 1250�

Cell Organelles The organelles of a cell work together to carry

out the functions necessary for cell survival.

Gateway to the CellAccording to the fluid mosaic model, the

plasma membrane is formed by two layers ofphospholipids with the fatty acid chains facingeach other; the phosphate groups face the cell’sinternal and external environments, and proteinsare embedded in the membrane.

Control of Cell FunctionsThe nucleus contains the master plans for pro-

teins, which are then produced by organellescalled ribosomes. The nucleus also controls cellularfunctions.

Assembly, Transport, and Storage The cytoplasm suspends the cell’s organelles,

including endoplasmic reticulum, Golgi apparatus,vacuoles, and lysosomes. The endoplasmic reticulumand Golgi apparatus transport and modify proteins.

Energy Transformers Chloroplasts are found in plant cells. They

capture the sun’s light energy so it can be trans-formed into useable chemical energy. Mitochon-dria are found in both animal and plant cells. They transform the food you eat into a useableenergy form.

Support and LocomotionA network of microfilaments and microtubules

attach to the plasma membrane to give the cellstructure. Cilia are short, numerous projections thatmove like the oars of a boat. Flagella are longerprojections that move in a whiplike fashion to propel a cell.

(l)Biophoto Associates/Photo Researchers, (r) Dr. Gopel Murti/Phototake, NYC


The Life of a Cell

Cellular EnvironmentsIsotonic solution: same number of dissolvedsubstances inside and outside the cellHypotonic solution: more dissolved sub-stances inside the cell; water enters the cellHypertonic solution: fewer dissolved sub-stances inside the cell; water leaves the cell

ATP production for eachmolecule of glucoseGlycolysis: produces a net gain of two ATP,two NADH, and two H+

Citric acid cycle (Krebs cycle): producestwo ATP, six NADH, and two FADH2Electron transport chain: produces 32 ATPfrom NADH and FADH2Lactic acid fermentation: produces two ATPand lactic acid

THE LIFE OF A CELL 247

Interphase

Prophase

Metaphase

Anaphase

Telophase

During the stages of mitosis, chromosomes are sepa-rated into two daughter cells.

Carrier protein

Higher concentrationof ions

Ions Lower concentrationof ions Energy

Active transport

Diffusion and OsmosisThe selectively permeable plasma membrane

allows only certain substances to cross. Diffusion is the movement of a substance from an area ofhigher concentration to an area of lower concen-tration. Diffusion of water across a selectively per-meable membrane is called osmosis.

Simple diffusion occurs by random movementof molecules or ions. In facilitated diffusion, pro-teins bind to and move molecules across a mem-brane. Active transport uses energy to movemolecules against a concentration gradient.

Energy in a Cell Adenosine triphosphate (ATP) is the most com-

mon energy source in a cell. Two organelles helpform ATP from other sources of energy.

Chloroplasts in plant cells convert energy fromthe sun’s rays into ATP using light-dependent reac-tions and store that energy in sugars via light-independent reactions and the Calvin cycle.

Mitochondria in both plant and animal cells con-vert food energy into ATP through a series ofchemical reactions including glycolysis, the citricacid cycle, and the electron transport chain.

MitosisAs cells grow, they reach a size where the

plasma membrane cannot transport enough nutri-ents and wastes to maintain cell growth. At thispoint, the cell undergoes mitosis and divides.

The period prior to mitosis, called interphase, isone of intense metabolic activity. The first stage ofmitosis is prophase, when the duplicated chromo-somes condense and the mitotic spindle forms. Thechromosomes line up in the center of the cell dur-ing metaphase and slowly separate during ana-phase. In telophase the nucleus divides followedby cytokinesis, which separates the daughter cells.


248 UNIT 3 STANDARDIZED TEST PRACTICE

Chromosome Comparison of Four Organisms

Organism Human Rye Potato Guinea pig

Number of chromosomes 46 14 48 64in body cells

Number of chromatids 92 A 96 128during metaphase

Number of chromosomes 46 14 48 64in daughter cells

Multiple Choice

Use the table below to answer questions 1–3.

1. What number belongs in the space labeled Aunder “Rye” in the table?A. 14 C. 7B. 28 D. 21

2. If one pair of chromatids failed to separateduring mitosis in rye cells, how many chromo-somes would end up in the two daughter cells?A. 28 and 28B. 14 and 14C. 7 and 8D. 13 and 15

3. What is the relationship between the numberof chromosomes in body cells and the com-plexity of an organism?A. The more complex the organism, the more

chromosomes it has.B. The more complex the organism, the fewer

chromosomes it has.C. There is no relationship.D. The number of chromosomes is deter-

mined by the sex of the organism.

4. The isotopes of the element magnesium differin their number of ________.A. proteinsB. electronsC. neutronsD. protons

5. Which of the following organelles are found inall cells?A. plasma membrane and ribosomesB. mitochondria and chloroplastsC. microtubules and lysosomesD. Golgi apparatus and endoplasmic reticulum

6. During late interphase, the chromosomes dou-ble to form chromatids that are attached toeach other. During which phase of mitosis dothe chromatids separate?A. prophaseB. metaphaseC. anaphaseD. telophase

7. Plants must have a constant supply of ________for photosynthesis, but they provide ________for cellular respiration.A. water—carbon dioxideB. carbon dioxide—waterC. carbon dioxide—oxygenD. oxygen—water

8. Which type of bond involves the sharing of electrons?A. covalentB. ionicC. hydrogenD. electrostatic

9. The primary organelle used for storing infor-mation in a cell is the ________.A. cell wallB. endoplasmic reticulumC. mitochondriaD. nucleus

When Eliminating,Cross It Out

List the answer choice letters on scratch paperand, with your pencil, cross out choices you’veeliminated. You’ll stop yourself from choosingan answer you’ve mentally eliminated.

B.1.8

B.1.8

B.1.8

B.1.3

B.1.8

B.1.3

The assessed Indiana standard appears next to the question.End-of-Course Assessment Practice


UNIT 3 STANDARDIZED TEST PRACTICE 249

10. A biologist studies cells under a microscopethat have been drawn from an unknown solu-tion. The cells appear shriveled. What can thebiologist conclude about the solution? A. It is hypotonic.B. It is isotonic.C. It is hypertonic.D. It is polar.

11. Which helps capture the sun’s energy?A. light-dependent reactionsB. citric acid cycleC. Calvin cycleD. light-independent reactions

Use the word equation below to answer questions12–14.

sucrose � water glucose � fructose

12. The reaction above illustrates the ________.A. hydrolysis of sucroseB. condensation of sucroseC. hydrolysis of glucoseD. condensation of fructose

13. The product(s) of this reaction is/are________.A. sucroseB. waterC. glucose and fructoseD. sucrose and water

14. Glucose and fructose are ________.A. disaccharidesB. polysaccharidesC. monosaccharidesD. starches

Use the figure below to answer questions 15–17.

15. The illustrations above demonstrate the trans-port of an ion across the plasma membrane,but they are out of sequence. In what order dothey belong?A. D-C-B-A C. C-B-D-AB. A-B-D-C D. A-D-B-C

16. What statement is true about diagram D?A. The ion movement is random.B. Energy is required.C. The fatty acids in the plasma membrane

could also move apart to allow the ionthrough.

D. The concentration of ions is higher at thetop of diagram D than at the bottom.

17. Which process is best represented by these diagrams?A. diffusion C. endocytosisB. active transport D. passive transport

Energy

A. B.

C. D.

Constructed Response/Grid In

Record your answers on your answer document.

18. Open Ended How is an ionic bond different from a covalent bond?

19. Open Ended Describe the role of transport proteins in plasma membranes.

20. Open Ended Compare the functions of mitochondria and chloroplasts in cells. Be sure to includeATP in your answer.

21. Open Ended Describe the cellular process of mitosis.

B.1.2

B.1.3

B.1.8

B.1.2

B.1.2

B.1.2

in.bdol.glencoe.com/standardized_test


http://in.bdol.glencoe.com/standardized_test

Chapter 9: Energy in a Cell - bcsc.k12.in.us · active transport:movement of materials through a...

Documents

Transcript of Chapter 9: Energy in a Cell - bcsc.k12.in.us · active transport:movement of materials through a...