HW: Chapter 6
Consider how cells obtain energy to make ATP. The chemical that serves as the electron donor is the ________ source, and the one that ultimately accepts those electrons is the _________ electron acceptor.
energy or electron; terminal or final
The sum total of all chemical reactions in a cell is called _________.
metabolism
In addition to yielding energy, catabolic pathways generate carbon intermediates that can be used in anabolic pathways for the biosynthesis of macromolecules. These carbon skeletons are called _________ _________.
precursor metabolites
Considering the general equation that describes photosynthesis, the rate of the process would be most influenced by the availability of _______ in the atmosphere. Multiple choice question. H2 N2 O2 CO2
CO2
Cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversibly and distort them. This control of enzymes is called _____________ regulation.
allosteric, noncompetitive, or non-competitive
Proteins are hydrolyzed by proteases, enzymes that break the peptide bonds between _______ ________ subunits
amino acid
The Calvin cycle is a two-step linear pathway that photosynthetic organisms use to fix carbon dioxide a. True - The pathway is complex and cyclic. b. False
b. False
A cell has only a limited number of electron carrier molecules. During glycolysis, if electrons are not removed from NADH, the cell soon runs out of available NAD+, and the breakdown of glucose ends. This presents a problem for cells that lack a suitable terminal electron acceptor for the electron transport chain or that cannot respire. The solution to this problem is a process called ____________.
fermentation
If the theoretical maximum ATP yield in prokaryotes from oxidative phosphorylation is 34 ATP for a single glucose molecule, what is the total ATP gain when substrate-level phosphorylation is included? Multiple choice question. 68 ATP 76 ATP 4 ATP 38 ATP 34 ATP
38 ATP
When a molecule other than O2 serves as the terminal electron acceptor for the electron transport chain, the organism is utilizing ______ respiration.
anaerobic
In a biosynthetic pathway, the end product generally acts as the allosteric inhibitor, allowing the cell to shut down the pathway when the product begins accumulating. This mechanism of control is called feedback ______.
inhibition
The reactions that capture radiant energy and convert it into chemical energy in the form of ATP are called the __________ - ___________ reactions
light-dependent
Starch and cellulose are both polymers made up of the monosaccharide __________, which means that hydrolysis of the polymers releases subunits that can enter directly into the central metabolic pathway of ____________to be oxidized.
glucose, glycolysis
Microorganisms that can grow on polysaccharides and disaccharides first break these down to glucose or precursor metabolites that can then enter into the pathway of ___________ to be oxidized.
glycolysis
In aerobic respiration, __________ serves as the terminal electron acceptor.
oxygen O2
After a deamination reaction removes the amino group from amino acids, the remaining carbon skeletons are converted into the appropriate __________ metabolites for entry into central metabolic pathways.
precursor
The primary pathway used by many organisms to convert glucose to pyruvate is ________.
glycolysis or Embden-Meyerhoff
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a _________ pathway.
metabolic
Prokaryotes are remarkably diverse in their metabolism. Many are _________ anaerobes which use O2 if it is available, but they can use an alternative if it is not.
facultative
The mechanism by which cellular respiration uses reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP is )______________ phosphorylation.
oxidative
The three central metabolic pathways that gradually oxidize glucose to CO2 are ______________ , the _________ ___________pathway, and the _____________cycle.
glycolysis/ pentose phosphate/ Krebs, citric acid, TCA, or tricarboxylic acid
Each enzyme functions best within a narrow range of environmental conditions. Three important environmental conditions that influence enzyme activity are ___________, __________ and salt concentration.
temperature, pH
The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______. Multiple choice question. a. after; synthesize organic compounds from CO2 b. before; synthesize organic compounds from CO2 c. before; breakdown glucose to CO2 and H2O d. before; generate ATP and reducing power e. after; generate ATP and reducing power
a. after; synthesize organic compounds from CO2
In addition to glucose, which of the following organic compounds can serve as energy sources for microbes? Multiple select question. a. lipids b. polysaccharides c. disaccharides d. proteins e. monosaccharides f. fatty acids g. phosphate Reason: This is not an organic molecule.
a. lipids b. polysaccharides c. disaccharides d. proteins e. monosaccharides f. fatty acids
An organism that uses hydrogen sulfide as an energy source is called a _______ and is most likely _______. Multiple choice question. a. chemoorganotroph; eukaryotic b. chemolithotroph; eukaryotic c. chemoorganotroph; prokaryotic d. chemolithotroph; prokaryotic
d. chemolithotroph; prokaryotic
The biochemical reactions in metabolism where the simple molecules combine to generate macromolecules is known as _______. Multiple choice question. a. amensalism b. metabolism Reason: This involves both anabolism and catabolism. c. anabolism d. catabolism
c. anabolism
The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes __________ and _____________ and then pass these electrons along the chain.
NADH/ FADH2 or FADH
Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions? Multiple choice question. O2, NADPH, and ATP O2, NADPH, and glucose CO2, NADPH, and ATP NADH and ATP NADPH and ATP
NADPH and ATP
hen a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical things? Multiple choice question. a. ATP, reducing power, precursor metabolites b. ADP, NADH, glucose Reason: Remember, the three key items generated are ATP, reducing power, and precursor metabolites. c. ATP, NAD+, pyruvate Reason: Remember, the three key items generated are ATP, reducing power, and precursor metabolites. d. ATP, reducing power, ethanol Reason: Remember, the three key items generated are ATP, reducing power, and precursor metabolites. e. ADP, reducing power, lactic acid Reason: Remember, the three key items generated are ATP, reducing power, and precursor metabolites.
a. ATP, reducing power, precursor metabolites
Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true? Multiple select question. a. In photosynthetic organisms, the process is called the light-independent reactions. b. It often involves the Calvin cycle. c. It is called carbon fixation. d. Plants accomplish it by reversing the steps of the TCA cycle. Reason: This is the case with green bacteria and some Archaea.
a. In photosynthetic organisms, the process is called the light-independent reactions. b. It often involves the Calvin cycle. c. It is called carbon fixation.
The set of chemical reactions that degrade compounds, releasing their energy is termed ______. Multiple choice question. a. metabolism Reason: This involves both catabolism and anabolism. b. catabolism c. amensalism d. anabolism
b. catabolism
Some members of which of the following groups can use inorganic chemicals such as hydrogen sulfide and ammonia for energy? Multiple choice question. a. Prokaryotes only b. Eukaryotes and prokaryotes c. Eukaryotes only
a. Prokaryotes only
Metabolism is best defined as ______. a. the sum total of all chemical reactions in a cell b. the way in which organisms obtain food c. digestion of food d. the manner in which cells grow
a. the sum total of all chemical reactions in a cell
Certain intermediates of catabolic pathways, called precursor metabolites, are important because ______. Multiple choice question. a. they serve as carbon skeletons from which subunits of macromolecules can be made b. they are required for the function of certain enzymes Reason: Recall that cofactors are non-protein components that assist certain enzymes. c. they are required before the breakdown of glucose can occur. Reason: Remember, precursor metabolites represent intermediates of catabolic pathways, i.e., components produced from the breakdown or molecules such as glucose.
a. they serve as carbon skeletons from which subunits of macromolecules can be made
The component of metabolism that involves the biosynthesis of macromolecules, using ATP for energy, is called _________.
anabolism
Consider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways? Multiple select question. a. water Reason: Although water is indeed produced at the end of the electron transport chain during aerobic respiration (as opposed to by central metabolism of glucose), remember that it is a by-product. b. ATP c. large carbon polymers Reason: Recall that central metabolism generates precursor molecules. These can then be assembled into various macromolecules by anabolic pathways. d. CO2 Reason: Although CO2 is indeed produced by central metabolic pathways, remember that it is just a by-product. e. oxidized electron carriers Reason: Recall that central metabolism generates reducing power, which is in the form of reduced electron carriers. f. reducing power g. precursor metabolites
b. ATP f. reducing power g. precursor metabolites
Until the optimal temperature is reached, raising the temperature has what effect on the speed of enzymatic reactions? Multiple choice question. a. It decreases their rate. b. It increases their rate. c. It has no effect on their rate.
b. It increases their rate.
All of the following accurately describe enzymes EXCEPT ______. Multiple choice question. a. enzymes are very specific, usually acting on only one or a few substrates b. enzymes provide energy to help reactions proceed more rapidly c. the name of an enzyme typically reflects its function and ends in -ase d. enzymes are biological catalysts e. enzymes are not used up in the process of catalyzing reactions Reason: This statement is true. Enzymes are neither used up nor permanently changed during a reaction.
b. enzymes provide energy to help reactions proceed more rapidly
In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are ______. Multiple choice question. a. glucose and carbon dioxide b. glucose and oxygen c. carbon dioxide and oxygen d. water and carbon dioxide
b. glucose and oxygen
Metabolic pathways can be linear, _________, or __________.
branched or branch; cyclical, cyclic, or cycle
The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called ________ _________.
carbon fixation
Fats are hydrolyzed by lipases. The glycerol component is then converted to a precursor metabolite, and the fatty acids are degraded using a series of reactions called β-oxidation that remove successive 2-carbon units. Where do these components enter the central metabolic pathways for further oxidation? Multiple choice question. a. Glycerol is converted to glucose; the fatty acids enter directly into the TCA cycle. b. The precursor metabolites from glycerol enter the pentose phosphate pathway; the fatty acids are converted to glucose and enter glycolysis. c. The precursor metabolites from glycerol are joined together to form pyruvate; the 2-carbon units from fatty acids are combined to form glucose. d. The precursor metabolites from glycerol enter glycolysis; the 2-carbon units from fatty acids are added to coenzyme A and enter the TCA cycle.
d. The precursor metabolites from glycerol enter glycolysis; the 2-carbon units from fatty acids are added to coenzyme A and enter the TCA cycle.
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will ____________ and no longer function.
denature
Fats, the most common simple lipids, are broken down by lipases into their component ______. Multiple choice question. a. monosaccharides b. single carbons and hydrogens c. amino acids d. glycerol and amino acids e. glycerol and fatty acids
e. glycerol and fatty acids
Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true? Multiple select question. a. It often involves the Calvin cycle. b. In photosynthetic organisms, the process is called the light-independent reactions. c. It is called carbon fixation. d. Plants accomplish it by reversing the steps of the TCA cycle. Reason: This is the case with green bacteria and some Archaea.
a. It often involves the Calvin cycle. b. In photosynthetic organisms, the process is called the light-independent reactions. c. It is called carbon fixation.
What are the two fundamental tasks that all cells must accomplish to grow? Multiple choice question. a. Synthesize new parts and harvest energy to power reactions. b. Consume food and digest food. c. Grow and undergo binary fission. d. Mate and produce offspring. e. Undergo cell division and avoid dessication.
a. Synthesize new parts and harvest energy to power reactions.
Which of the following are reasons an organism might use fermentation? Multiple select question. a. They lack an electron transport chain. b. The energy yield is greater from fermentation than from respiration. Reason: The ATP yield from fermentation is much lower than if glucose is oxidized all the way to CO2. The pyruvate (or derivative) used as a terminal electron acceptor in fermentation still contains a great deal of energy. c. They lack the ability to perform glycolysis. Reason: Remember, fermentation relies upon glycolysis to split glucose and generate 2 ATP via substrate-level phosphorylation. d. A suitable inorganic terminal electron acceptor is not available.
a. They lack an electron transport chain. d. A suitable inorganic terminal electron acceptor is not available.
Which of the following are true statements about what happens to glucose inside a cell? Multiple select question. a. All the glucose molecules are oxidized to CO2, generating ATP and reducing power in the process. Reason: Remember, this would generate the maximum energy yield, but it is likely the cell will also have biosynthetic needs and will therefore siphon off some precursor metabolites for anabolism. b. Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. c. Some glucose might be oxidized to CO2, generating the maximum amount of ATP. d. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis.
b. Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. c. Some glucose might be oxidized to CO2, generating the maximum amount of ATP. d. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis.
For each six-carbon molecule of glucose that enters glycolysis, how many molecules of pyruvate are made, and how many carbon atoms does each pyruvate have? Multiple choice question. a. Six molecules of pyruvate, each with one carbon atom. b. Two molecules of pyruvate, each with three carbon atoms. c. Two molecules of pyruvate, each with two carbon atoms. Reason: Two molecules of pyruvate are made, but remember that each has three carbon atoms (glucose has six carbon atoms). d. One molecule of pyruvate with six carbon atoms. e. Three molecules of pyruvate, each with two carbon atoms.
b. Two molecules of pyruvate, each with three carbon atoms.
Enzymes are biological ______ that are typically _______. Multiple choice question. a. catalysts; lipid b. catabolites; protein c. catalysts; protein d. catabolites; lipid e. reducters; protein
c. catalysts; protein
Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an ______. Multiple choice question. a. terminal electron acceptor b. precursor metabolite c. energy source
c. energy source
One component of metabolism, called ________ , involves the breakdown of compounds to release energy.
catabolism
The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.
catabolism; anabolism
The ATP generated by fermentation comes from ______. Multiple choice question. a. substrate-level phosphorylation during glycolysis b. oxidative phosphorylation driven by NADH Reason: Oxidative phosphorylation refers to the reducing power generated by the central metabolic pathways being donated to an electron transport chain to create a proton motive force that is used to generate ATP via ATP synthase. c. the reducing power obtained from the oxidation of glucose Reason: In fermentation, the electrons removed from glucose are donated to pyruvate or another organic derivative in order to regenerate NAD+ so that glycolysis can continue. d. the tricarboxylic acid (TCA) cycle Reason: During fermentation, the TCA cycle is either not functioning due to the lack of an appropriate terminal electron acceptor in respiration or because the organism lacks an electron transport chain.
a. substrate-level phosphorylation during glycolysis
In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish? Multiple choice question. a. They use sunlight to convert CO2 into sugars by carbon fixation. Reason: Carbon fixation is part of the dark reactions or light-independent reactions. b. They are the reactions of the Calvin cycle, which fix CO2. c. They use ATP to synthesize organic compounds. d. They capture radiant energy and convert it to chemical energy in the form of ATP.
d. They capture radiant energy and convert it to chemical energy in the form of ATP.
Glucose catabolism encompasses two key processes: (1) oxidizing glucose molecules to generate ATP, reducing power, and precursor metabolites; and (2) transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor. The second process, transfer of electrons, is accomplished as part of which of the following? Multiple select question. a. cellular respiration b. the TCA cycle Reason: Remember, the TCA cycle is one of the central metabolic pathways, so it is involved in (1). c. fermentation d. the pentose phosphate pathway Reason: Remember, the pentose phosphate pathway is one of the central metabolic pathways, so it is involved in (1). d. glycolysis Reason: Remember, glycolysis is one of the central metabolic pathways, so it is involved in (1).
a. cellular respiration c. fermentation
Which of the following explain why a cell might undergo fermentation? Multiple select question. a. The cell might not have the appropriate terminal electron acceptor available for respiration. b. The cell can obtain more ATP from this pathway than via respiration. Reason: Recall that respiration actually generates the most ATP from the overall breakdown of glucose, far more than the 2 net ATP that fermentation (via glycolysis) generates. c. This allows the cell to grow in the presence of O2, which otherwise it would be unable to do. Reason: Actually, the ability to grow in the presence of O2 does not depend on fermentation. Obligate aerobes must grow in the presence of O2. And fermentation can occur in either the presence or absence of O2. d. The cell has a limited number of electron carrier molecules that must be regenerated for glycolysis to continue. e. The cell might lack the pathways for respiration, so fermentation might be the only option.
a. The cell might not have the appropriate terminal electron acceptor available for respiration. d. The cell has a limited number of electron carrier molecules that must be regenerated for glycolysis to continue. e. The cell might lack the pathways for respiration, so fermentation might be the only option.
Although the actual procedure is much more involved, the basic metabolism of wine-making involves inoculating grape juice with a special strain of the yeast Saccharomyces cerevisiae. S. cerevisiae will preferentially perform aerobic respiration on sugars in the juice but can also ferment those sugars to yield CO2 and alcohol, an important component of wine. Assume you inoculate a completely full container of juice and then close the lid. What will the yeast do? Multiple choice question. a. They will grow aerobically, consume the O2 dissolved in the juice, and then switch to fermenting sugars to yield alcohol. b. They will grow aerobically until all the O2 is gone and then stop, because aerobic respiration yields the greatest energy. c. They will only ferment the sugars to yield alcohol. d. They will grow aerobically, then switch to anaerobic respiration as the O2 level drops. e. They will grow aerobically on the sugars, producing O2 in the process.
a. They will grow aerobically, consume the O2 dissolved in the juice, and then switch to fermenting sugars to yield alcohol.
All of the following represent the two fundamental tasks cells need to accomplish in order to grow EXCEPT ______. a. sexual reproduction b. synthesizing cell membranes c. converting energy into a form that can power energy-consuming reactions d. production of ribosomes e. harvesting energy
a. sexual reproduction
Oxidative phosphorylation, the mechanism by which cellular respiration uses the NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps? Multiple select question. a. The electron transport chain uses the energy in protons to transfer electrons across the membrane. Reason: Remember, the electron transport chain uses the energy of electrons to drive protons across the membrane. b. The electron transport chain generates a proton motive force. c. Electrons flow through ATP synthase to drive the synthesis of ATP. Reason: Remember, it is the flow of protons through ATP synthase that drives the synthesis of ATP. d. The electron transport chain is oxidized by the donation of electrons from NADH and FADH2. Reason: Remember, the donation of electrons to the electron transport chain actually reduces the electron transport chain. The electron carriers NADH and FADH2 are oxidized by this donation back to NAD+ and FAD. e. ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP. f. A phosphate group is removed from each NADH and FADH2. Reason: Remember, NADH and FADH2 are reduced electron carriers; their job
b. The electron transport chain generates a proton motive force. e. ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP.
The Calvin cycle ______. Multiple choice question. a. captures radiant energy, thereby allowing photosynthesis b. incorporates carbon dioxide into organic compounds c. is used by chemoorganoheterotrophs
b. incorporates carbon dioxide into organic compounds
During cellular metabolism, three key metabolic pathways together gradually _______. These are collectively referred to as the central metabolic pathways. Multiple choice question. a. reduce glucose to O2 b. reduce glucose to CO2 c. oxidize glucose to CO2 d. oxidize glucose to O2
c. oxidize glucose to CO2
In biosynthetic pathways, feedback inhibition refers to ______. Multiple choice question. a. the mechanism to reduce expression of genes coding for the enzymes Reason: Remember, feedback inhibition refers to the end product acting as an allosteric inhibitor of the pathway. b. the starting compound acting as a competitive inhibitor of the pathway Reason: Remember, feedback inhibition refers to the end product acting as an allosteric inhibitor of the pathway. c. the end product acting as an allosteric inhibitor of the pathway d. the decrease in production of related compounds in response to production of the end product Reason: Remember, feedback inhibition refers to the end product acting as an allosteric inhibitor of the same pathway, not a decrease in production of other pathways.
c. the end product acting as an allosteric inhibitor of the pathway
In order for cells to obtain energy, they remove electrons from an energy source and ultimately donate them to the terminal electron acceptor. What does this tell us about the electron affinity of the energy source and the terminal electron acceptor? Multiple choice question. a. This information doesn't tell us anything about the electron affinities of these molecules. Reason: In order for electrons to move from the energy source to the terminal electron acceptor, the energy source must have a lower affinity for electrons than the terminal electron acceptor. b. The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons. c. The energy source and the terminal electron acceptor have equal but opposite electron affinities. Reason: Recall that chemicals with a low electron affinity tend to donate electrons, whereas those with a high affinity tend to accept electrons. d. The energy source has a higher affinity for electrons, and the terminal electron acceptor has a lower affinity for electrons. Reason: Remember, a lower affinity for electrons means the chemical tends to give them up. A high affinity means the chemical is more li
b. The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons.
Microorganisms can grow on a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this? Multiple choice question. a. They extract the glucose structures from these macromolecules and excrete the rest as waste products into the surrounding environment. Reason: Most macromolecules do not directly have a glucose structure. Instead, they are broken apart into precursor metabolites, which can then be introduced into the appropriate central metabolic pathways of the cell, or used in biosynthesis. b. They have separate metabolic pathways for these three classes of macromolecules that oxidize the compounds to CO2. Reason: Remember, cells process the macromolecules down to appropriate precursor metabolites that can then be introduced into the correct central metabolic pathways. c. They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis. d. A series of enzymatic reactions convert the proteins, lipids, and polysaccharides into glucose that can then be broken down via glycolysis Reason: Rather than convert all the macromolecules into glucose
c. They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis.
Other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do the additional steps of fermentation accomplish? Multiple choice question. a. They generate end products such as ethanol, which the cell can then use as an energy source. Reason: Remember, from the perspective of the cell that generated the ethanol or other substance, it is simply a waste product. It still contains plenty of energy (which another organism could utilize!) b. They use up extra ATP so that glycolysis can continue producing additional reducing power. Reason: Recall that fermentation regenerates NAD+ so that glycolysis can continue. c. They consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going. d. They produce end products, such as ethanol or lactic acid, which are used to inhibit the growth of competitors. Reason: Although products of fermentation can indeed inhibit the growth of other microorganisms, that is not the main purpose of fermentation. The organism is using the pyruvate or derivative from the end of glycolysis as a terminal electron acceptor in order to regenerate NAD+ so that glycolysis can
c. They consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going.
