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Are NADH and FADH2 reduced or oxidized electron carriers?
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Define respiration
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Chapter 10 MicrobioE
Exam 2
| Question | Answer |
|---|---|
| Are NADH and FADH2 reduced or oxidized electron carriers? | reduced |
| Define respiration | when an organic energy source is oxidized, electrons are released and accepted by electron carriers NAD+ and FAD. These now reduced electron carriers donate electrons to an electron transport chain |
| What is the final electron acceptor in aerobic respiration | oxygen |
| what is the terminal electron acceptor in anaerobic respiration | a different molecule such as NO3-, SO4-2, CO2, Fe+3, and SeO4-2. also fumarate and humic acid |
| as electrons pass through the chain to the terminal electron acceptor, what is generated? | proton motive force (PMF) |
| what is the proton motive force used for? | used to synthesize ATP from ADP and Pi. |
| What kind of electron acceptor does fermentation use? | an endogenous electron acceptor (within the cell) that does not involve an electron transport chain |
| What is usually the endogenous electron acceptor? | an intermediate of the catabolic pathway used to degrade and oxidize organic energy source. usually pyruvate |
| What is ATP almost exclusively synthesized by? | substrate-level phosphorylation |
| What is substrate level phosphorylation? | a process where phosphate is transferred to ADP from a high energy molecule |
| What is the energy source for aerobic respiration, anaerobic respieration, and fermentation | glucose |
| The existence of a few metabolic pathways is good because.... | each degrading many nutrients greatly increases metabolic efficiency by avoiding the need for a large number of less metabolically flexible pathways |
| what catabolic pathways are of hte greatest importance to chemoorganotrophs? | glycolytic pathways |
| How are the enzyme-catalyzed reactions arranged | arranged so that the product of one reaction serves as a substrate for the next |
| What is the importance of glycolytic pathways for anabolism | 1.) supply needed materials for biosynthesis such as precursor metabolites and reducing power 2. Enzymes of these pathways are reversible and can function either catabolically or anabolically |
| What are precursor metabolites used for> | serve as the starting material for biosynthetic pathways |
| what is reducing power used for | used in redox reactions that reduce the precursor metabolites as tehy are transformed into amino acids, nucleotides, and other molecules needed for synthesis of macromolecules |
| What are pathways that can function both catabolically and anabolically referred to as | amphibolic pathways |
| T or F: many of the enzymes of hte Embden-Meyerhof pathway are freely reversible | true |
| when do the enzymes of the Embden-Meyerhof function catabolically | during glycolysis |
| when do the enzymes of the Embden-Meyerhof function anabolically | during gluconeogenesis |
| What is the main difference between anaerobic and aerobic respiration? | the terminal electron acceptor |
| What is the process that can completely catabolize an organic energy source in CO2 using the glycolytic pathways and TCA cycle with O2 as the terminal electron acceptor for an electron transport chain | aerobic respiration |
| What yields the most ATP during aerobic respiration? | functioning of the electron transport chain |
| What are three metabolic pathways that microorganisms use to catabolize glucose to pyruvate? | 1. Embden-Meyerhof pathway 2. Entner-Doudoroff pathway 3. Pentose Phosphate pathway |
| What are the three pathways collectively referred to as? | glycolysis or glycolytic pathways |
| Is the Embden-Meyerhof pathway an amphibolic pathway? | yes |
| What reverses the glycolytic process and allows cells to synthesize glucose from smaller molecules like pyruvate | gluconeogenesis |
| Where does the Embden-Meyerhof occur | in the cytoplasm |
| Does the EMP function any differently in the presence or absence of O2 | no |
| what does EMP provide for the cell | provides several precursor metabolites, NADH,and ATP for the cell |
| What are the two parts of the EMP pathway | 1. preliminary phase that "primes the pump" by adding phosphates to each end of the sugar (investment of ATP) 2. three-carbon energy conserving phase where fructose-1,6-bisphosphate is divided into two halves |
| Give an example of substrate level phosphorylation | when the first carbon of 1,3-bisphosphoglycerate is donated to ADP to produce ATP. ADP phosphorylation is coupled with the exergonic hydrolysis of a high energy molecule having a higher phosphate transfer potential then ATP |
| what is the last intermediate in the Embden-Meyerhof pathway | phosphoenolpyruvate |
| what is dihydroxyacetone phosphate immediately converted to in the EMP | glyceraldehyde-3-phosphate |
| What is NADH used for duing aerobic respiration | to transport electrons to an electron transport chain |
| what is the starting molecule for the pnetose phosphate pathway | glucose-6-phosphate |
| is glucose-6-phosphate an aldehyde | yes |
| is fructose-6-phospate a ketone | yes |
| What is the most important precursor metabolite | pyruvate |
| Does embden-meyerhof pathway funcction during aerobic, anaerobic, and fermentation | yes |
| Name the precursor metabolites in the EMP | Glucose-6-phospate, fructose-6-phosphate, glyceraldehyde-3-phosphate, 3-phosphoglycerate, phosphoenolpyruvate, and pyruvate |
| What are the electrons accepted by in respiration | an exogenous electron acceptor |
| what are the electrons donated by NAD+ in fermentation accpeted by | an endogenous electron acceptor (pyruvate) |
| What organisms use the Entner-Doudoroff pathway | soil bacteria like pseudomonas, rhizobium, azotoboacter, and agrobacterium and a few other gram negative bacteria |
| what is the only gram positive bacteria to use the Entner-Doudoroff pathway | enterococcus faecalis |
| What is the relationship between the Entner-Doudoroff pathway and the EMP | the EDP essentially replaces the first phase of the EMP to yield pyruvate and glyceraldehyde-3-phosphate |
| What is a key intermediate of the Entner-Doudoroff pathway | 2-keto-3-deoxy-6-phosphogluconate |
| T of F: bacteria that use the EDP also have the enzymes that function in the second phase of the EMP that are used to catabolize the glyceraldehyde-3-phosphate to form a second pyruvate molecule | true |
| what is another name for the pentose phosphate pathway | the hexose monophosphate pathway |
| true or false: the pentose phosphate pathway can operate either aerobically or anaerobically | true |
| what is the pentose phosphate pathway inmportanti in | biosynthesis and catabolism |
| why is the pentose phosphate pathway used in all organisms? | because of its role in providing reducing power and important precursor metabolites |
| What are the two important enzymes in the pentose phosphate pathway | transketolase and transaldolase |
| what does transketolase do in the pentose phosphate pathway | catalyzes the transfer of two carbon groups |
| what does transaldolase do in the pentose phosphate pathway | it transfers a three carbon group from sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate |
| What is one reason why the pentose pathway is an important amphibolic pathway | 1. NADPH produced serves as a source of electrons for reduction of molecules during biosynthesis |
| What metabolic pathway is the major source of reducing power for cells and why | the pentose phosphate pathway because it yields 2 NADPH per glucose |
| What are two important precursor metabolites in the pentose phosphate pathway | erythrose 5-phosphate and ribose 5-phosphate |
| what is erythrose 4-phosphate used for | to synthesize aromatic amino acids and vitamin B6 (pyridoxal) |
| what is ribose 5-phosphate used for | a major componenet of nucleic acids |
| Name another reason why the pentose phosphate pathway is importnat amphibolic pathway | 2. it produces two important precursor metabolites: erythrose 4-phosphate and ribose 5-phosphate while also functioning biosynthetically to supply hexose sugars (glucose needed for peptidoglycan synthesis) |
| Name one last reason why the pentose phosphate pathway is important amphibolic pathway | 3. intermediates in the pathway can be used to produce ATP |
| What is another name for the Krebs cycle | tricarboxylic acid cycle or citric acid cycle |
| What is the first step of the krebs cycle | to use a multienzyme system called the pyruvate dehydrogenase |
| what forms the molecule acetyl-coenzyme A from pyruvate | pyruvate dehydrogenase |
| Why is acetyl-CoA energy rich | the hydrolysis of the bond that links acetic acid to coenzyme A has a large negative change in free energy |
| what kind of bond is coenzyme A | thioester bond |
| Name another high energy molecule in the krebs cycle that contains a thioester bond | succinyl CoA |
| What is GTP used for in the cell | used in protein synthesis and to make other nucleoside triphosphates including ATP |
| Where are krebs cycle enzymes located | in the cytoplasm in bacteria/archaea and in the mitochondria matrix in eukaryotes |
| what is the important role of the krebs cycle | energy conservation by producing numerous NADH and FADH2 |
| true or false: organisms that lack the complete krebs cycle usually have most of the cycle enzymes because the krebs cycle is also a key source of precursor metabolites for use in biosynthesis | true |
| How is ATP generated in the electron transport chain during respiration | from the oxidation of these electron carriers in the electron transport chain |
| Describe the electron transport chain | a series of electron carriers that operate together to transfer electrons from donors, like NADH and FADH2, to O2 |
| define "decarboxylated" | it loses a carbon in the form of CO2 |
| What can GTP be used for when made in the Krebs cycle | to make ATP or used directly to supply the energy to processes such as translation |
| How many stages may the cycle be divided into and based on what | three stages based on the size of its intermediates |
| what are these stages separated by | by two decarboxylation reactions |
| Name the precursor metabolites in the krebs cycle | pyruvate, acetyl CoA, Alpha-ketogluterate, succinyl CoA, and Oxaloacetate |
| In what direction between carriers (positive or negative reduciton potentials) do electrons travel | electrons flow from carriers with more negative reducing potential to thsoe with more positive potentials |
| How are the carriers constantly recycled | they are reduced and then reoxidized in the electrong transport chain |
| What makes possible the release of a great deal of energy between O2 and NADH | the large difference in reduction potentials between the two |
| What drives ATP synthesis | proton and electrical gradients in the electron transport chain |
| Where are ETC carriers in eukaryotes | in the inner membrane of the mitochondria |
| where is the electron transport chain in bacteria | within the plasma membrane |
| true or false: bacterial ETC's can be branced so electrons may enter the chain at several points and leave through several terminal oxidases | true |
| true or false: bacterial ETCs are shorter resulting in less energy release | true |
| Where are protons moved in bacteria as compared with eukaryotes | protons are moved across the plasma membrane to the periplasmic space in bacteria and are moved to the intermembrane space in the mitochondria of eukaryotes |
| what is oxidative phosphorylation | process by which ATP is synthesized as the result of electron transport driven by the oxidation of a chemical energy source |
| what is another name for oxidative phosphorylation | respiratory phosphorylation |
| what is the chemiosmotic potential | the ETC is organized so that protons move across the plasma membrane from the cytoplasm to the perisplasmic space as electrons are transported down the chain |
| who formulated the chemiosmotic potential | british biochemist Peter Mitchell |
| how does translocation of protons occur in the ETC | results from juxtaposition of carriers that accept both electrons and protons with carreirs that accept only cells |
| what is the Q cycle | the difference in protons and electrons carried sets the stage for this phenomenon that ultimately moves four protons across the membrane |
| what is the result of the proton expulsion during electron transport | formation of a concentration gradient of protons (chemical potential energy) and a charge gradient (electrical potential energy) |
| what is the alkalinity of the cytoplasm vs the periplasmic space | the cytoplasm is more alkaline and more negative than the periplasmic space |
| what is the alkalinity of the mitochondrial matrix vs. intermembrane space | the mitochondrial matrix is more alkaline then teh intermembrane space |
| what makes up the proton motive force | combined chemical and electrical potential differences |
| what is the proton motive force used for | to perform work when protons flow back across the membrane, down the concentration and charge gradients, and into the mitochondrial matrix. Also used to transport molecules into the cell directly and to rotate the bacterial flagella motor |
| Describe the flow of protons in the proton motive force | teh flow is exergonic and used to phosphorylate ADP to ATP |
| what catalyzes the use of proton motive force for ATP synthesis | ATP synthase |
| What are the two components of the ATP synthase multisubunit enzyme | F1 component: spherical structure attached to mitochondrial inner membrane surface by a stalk and F0: embedded in the membrane |
| where is the ATP synthase located | on the inner surface of the plasma membrane in bacteria |
| What does F0 participate in | proton movement across the membrane |
| where are the catalytic sites for ATP synthesis located | on the Beta subunits |
| Describe how ATP synthase functions | like a rotary engine; the flow of protons down the proton gradient through the F0 subunit causes F0 and teh y subunit to rotate |
| what happens as the y subunit rotates within the F1 | the conformation changes occur in the Beta subunits to allow entry of ADP and Pi into the catalytic site |
| Describe how ADP and Pi is changed to ATP | another conformation change loosely bind ADP and Pi in the catalytic site; ATP is synthesized when BetaDP conformation is changed to the BetaTP conformation and ATP is released when BetaTP changes to the BetaE conformation |
| What was the concept of phosphorus to oxygen (P/O) ratio | used prior to chemiosmotic hypothesis; used as a measure of the number of ATP molecule generated per oxygen |
| what occured with the acceptance of the chemiosmostic hypothesis | it was recognized taht the important measurement was the number of protons transported across the membrane by NADH oxidation and the number of protons consumed during synthesis of ATP |
| What are two factors that affect the yield of ATP from the catabolism of glucose by aerobic respiration | 1. the proton motive force generated by electron transport is used for functions other than ATP synthesis 2. the amphibolic nature of the pathways used to catabolize glucose |
| how is the amphibolic nature of the pathways affecting the ATP yield | for each molecule of glucose degraded, numerous precursor metabolites are made and for each one teh microbe must decide if that metabolite is needed for anabolism or it can continue the catabolic proces |
| true of false: the flow of electrons from glucose must be carefully monitored and regulated such that ATP production is appropriately balanced with biosynthesis | true |
| describe anaerobic respirations | the process where an exogenous terminal electron acceptor other than O2 is used for electron transport |
| what is the most common terminal electron acceptors used during anaerobic respiration | nitrate, sulfate, and CO2 |
| where is most of the ATP generated during anaerobic respiration made from | oxidative phosphorylation |
| describe dissimilatory nitrate reduction | the anaerobic reduction of NO3- makes it unavailable for assimilation into the cell |
| what kind of organism carries out only anaerobic respiration | obligate anaerobe |
| name an obligate anaerobe | methanogens |
| What terminal electron acceptor do obligate anaerobes use | CO2 or carbonate |
| what are possible reasons for reduction of ATP yield in anaerobic respiration | alternate electron acceptors have less positive reduction potentials than O2; the difference in reduction potentials between NADH and NO3- is smaller than that of O2 and NADH; |
| What is energy yield directly related to | the magnitude of the reduction potential difference |
| why is anaerobic respiration useful | it allows ATP synthesis by electron transport and oxidative phosphorylation in the absence of O2 |
| What do organisms that do fermentation lack that makes anaerobic respiration impossible | lack Electron transport chains or they repress the synthesis of ETC components under anoxic conditiosn making anaerobic respiration impossible |
| what happens if NAD+ is not regenerated | the oxidation of glyceraldehyde 3-phosphate will cease and glycolysis will stop |
| what four unifying themes need to be kept in mind when microbial fermentation is examined | 1. NADH is oxidized to NAD+ 2. O2 is not needed 3. the electron acceptor is often either pyruvate or a pyruvate derivative 4. ETC cannot operate, reducing the ATP yield per glucose significantly |
| true or false: in fermentation the substrate is only partially oxidized and ATP is formed in most organisms exclusively by substrate-level phosphorylation | true |
| do fermenting microbes need a proton motive force to work and to drive transport | yes |
| how do fermenting microbes create a proton motive force without an electron transport chain | they use ATP synthase in the reverse direction |
| how do fermentors use ATP synthase in reverse | ATP synthase pumps protons out of the cell, fueling this transport by the energy released when ATP is hydrolyzed to ADP and Pi |
| why is fermentation important for mirobes | it allows them to adjust to changes in their habitats |
| what are fermentation pathways named after | the major acid or alcohol produced by that particular microbe |
| what is the most common fermentation | lactic acid (lactate) fermentation; reduction of pyruvate to lactate |
| What do homolactic fermentors use | the Embden-Meyerhof pathway and directly reduce almost all the pyruvate to lactate with the enzyme lactate dehydrogenase |
| what do heterolactic fermentors form | substantial amounts of products other than lactate |
| what process is used when microbes ferment sugars to ehtanol and CO2 | alcoholic fermentation |
| what fermentation results in the excretion of ethanol and a mixture of acids, particuarly acetic, lactic, succinic, and formic acids | mixed acid fermentation |
| what organisms carry our mixed acid fermentation | escherichia, salmonella, and proteus |
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