Reading Essentials for Biology Glencoe (794133), страница 25
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What are the three stagesof cellular respiration?________________________________________________________________________96Chapter 9Cellular respiration is the process in which mitochondria breakdown food molecules to produce ATP. You will remember thatmitochondria are organelles in plants and animals that transformenergy for the cell. Cellular respiration has three stages: glycolysis, the citric acid cycle, and the electron transport chain.Glycolysis (gli KAH lih sis) is the first stage of cellular respiration. During glycolysis, a series of chemical reactions take place inthe cytoplasm of a cell. The reactions break down glucose, whichis a six-carbon sugar compound. The glucose is broken down intopyruvic (pie RUE vik) acid. Pyruvic acid is a three-carbon compound. Glycolysis produces two ATP molecules for every glucosemolecule that is broken down.What happens after glycolysis?After glycolysis is complete, the pyruvic acid molecules moveinto the mitochondria.The second stage of cellular respiration is called the citric acidcycle.
The citric acid cycle, also called the Krebs cycle, is a seriesof chemical reactions similar to the Calvin cycle, which you learnedabout in the last section. Like the Calvin cycle, the molecule usedin the first reaction of the citric acid cycle is also one of the endproducts. For every turn of the citric acid cycle, one molecule ofATP and two molecules of carbon dioxide are produced.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Cellular RespirationNameDateClassSection9.3Getting Energy to Make ATP, continuedThe electron transport chain is the third stage of cellular respiration. The electron transport chain in cellular respiration is likethe electron transport chains in the first phase of photosynthesis.The electrons are passed from protein to protein in the electrontransport chain and lose energy as they move down the chain.Some of this energy is used to make ATP.
Some is used by anenzyme to pump H+ ions into the center of the mitochondrion.As a result, the mitochondrion inner membrane becomes positively charged because of the high concentration of positivelycharged hydrogen ions. The gradient of H+ ions that resultsacross the inner membrane of the mitochondrion provides theenergy for ATP production.The final electron acceptor at the bottom of the chain is oxygen, which reacts with four hydrogen ions (4H+) and four electrons to form two molecules of water (H2O). This is why oxygenis so important to our bodies.
Without oxygen, the proteins in theelectron transport chain cannot pass along the electrons. If a protein cannot pass along an electron to oxygen, it cannot acceptanother electron. Very quickly, the entire chain becomes blockedand ATP production stops.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.FermentationSometimes your cells do not get oxygen for a short time. Thiscan happen during heavy exercise. When this happens, an anaerobic (a nuh RO bik) process called fermentation takes place.Anaerobic processes are those that do not need oxygen.Fermentation follows glycolysis. It interrupts the process ofcellular respiration.
It allows the cells to continue making ATPuntil oxygen is available again.2. When might your bodyperform fermentationprocesses?________________________________________________________________________How does lactic acid fermentation work?You know that under anaerobic conditions, the electron transport chain backs up because oxygen is not present as the finalelectron acceptor.
Lactic acid fermentation is a process thatsupplies energy when oxygen is not available. During lactic acidfermentation, pyruvic acid uses NADH to form lactic acid andNAD+, which is then used in glycolysis. This allows two ATPmolecules to be formed for each glucose molecule. The lacticacid is transferred from muscle cells, where it is produced duringstrenuous exercise, to the liver, which converts it back to pyruvicacid. The lactic acid that builds up in muscle cells results inmuscle fatigue.READING ESSENTIALSChapter 997NameDateClassSection9.3Getting Energy to Make ATP, continuedWhat is alcoholic fermentation?Alcoholic fermentation is a process used by some types ofbacteria and yeast cells to convert pyruvic acid into carbon dioxide (CO2) and ethyl alcohol. Bread gives us an example of alcoholicfermentation. The yeast cells in bread give off CO2 , which makesbubbles in the dough.
These bubbles make the bread dough rise.3. List two ways photosynthesis and cellular respiration are similar.________________________________________________________________________________________________As you remember, photosynthesis produces food moleculesand cellular respiration breaks down the food molecules. Thesetwo processes are very different, but they are also similar insome ways.Both photosynthesis and cellular respiration use electron carriers and a cycle of chemical reactions to form ATP. Both also useelectron transport chains in their processes.Even though these two processes use some similar tools, theresults are very different. Photosynthesis makes high-energycarbohydrates and oxygen.
Cellular respiration breaks down carbohydrates to make ATP and compounds that provide less energy.Also, one of the end products of cellular respiration is CO2, whichis one of the beginning products for photosynthesis. The oxygenproduced during photosynthesis is a critical molecule necessaryfor cellular respiration.
The table below compares photosynthesisand cellular respiration.Photosynthesis98Chapter 9Cellular RespirationFood synthesizedFood broken downEnergy from sun stored in glucoseEnergy of glucose releasedCarbon dioxide taken inCarbon dioxide given offOxygen given offOxygen taken inProduces sugarsfrom PGALProduces CO2 and H2ORequires lightDoes not require lightOccurs only inpresence ofchlorophyllOccurs in all living cellsREADING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Comparing Photosynthesisand Cellular RespirationNameDateClassSection9.3Getting Energy to Make ATP, continued◗ After You ReadMini Glossaryalcoholic fermentation: anaerobic process inwhich cells convert pyruvic acid into carbondioxide and ethyl alcohol; carried out bymany bacteria and fungi such as yeastsanaerobic (a nuh RO bik): chemical reactionsthat do not require oxygencellular respiration: chemical process wheremitochondria break down food moleculesto produce ATP; the three stages of cellularrespiration are glycolysis, the citric acidcycle, and the electron transport cyclecitric acid cycle: in cellular respiration, a series ofchemical reactions that break down glucoseand produce ATP; energizes electron carriersthat pass the energized electrons on to theelectron transport chainglycolysis: in cellular respiration, a series ofanaerobic chemical reactions in the cytoplasm that break down glucose into pyruvicacid; forms a net profit of two ATP moleculeslactic acid fermentation: a series of anaerobicchemical reactions in which pyruvic acid usesNADH to form lactic acid and NAD+, which isthen used in glycolysis; supplies energy whenoxygen for aerobic respiration is scarce1.
Read the key terms and definitions in the Mini Glossary above. List two terms that areanaerobic chemical reactions.____________________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.____________________________________________________________________________________2. Use the partially completed outline below to help you review what you have read about cellular respiration.
Fill in the blanks where missing information is needed.I. GlycolysisA. Chemical reactions break downB..is formed.II. Citric acid cycleA. Series ofB.used in first reaction is also available at end of cycle.C. Also called.III. Electron transport chainA.are passed from protein to protein.B.lose energy.C.formed.Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about getting energy to make ATP.READING ESSENTIALSChapter 999NameDateClassSection10.1 Mendel’s Laws of Heredity◗ Before You ReadSC.H.2.4.1 The student knows that scientists assume that the universe is a vast system inwhich basic rules exist that may range from simple to extremely complex, but that scientists operate on the belief that the rules can be discovered by careful, systematic study.Also covers SC.H.1.4.2Gregor Mendel was a mathematician and a monk.
Mendel used his skills in math to understand whysome characteristics are passed from parent to offspring and other characteristics are not. On thelines below, tell why you think having math skills is important in life.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentifyConcepts Highlight eachquestion head in this section.Then use a different color tohighlight the answers to thequestions.1. What is the differencebetween self-pollinationand cross-pollination?________________________________________________________________________100Chapter 10Gregor Mendel, an Austrian monk, discovered important factsabout heredity.
Heredity is the passing on of characteristics fromparents to offspring. These characteristics are called traits. Mendelwas the first person to predict which traits would be passed fromparents to offspring. The study of heredity is called genetics.Mendel used garden peas for his experiments. Garden peasproduce male and female sex cells called gametes. Fertilizationoccurs when the male sex cell unites, or joins, with the female sexcell. The united gametes form a new fertilized cell called a zygote(ZI goht). The zygote becomes part of a seed.In garden peas, as with most flowers, the male sex cells arethe grains of pollen.
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