Ch. 6
All of the following are essential for an electron transport chain to function EXCEPT ______.
ATP
The function of NAD+/NADH, NADP+/NADPH, and FAD/FADH2 in a cell is to carry
Blank 1: electrons or hydrogen
Consider the figure showing the formation and breakdown of ATP. Fill in the labels of the figure by matching the terms with their correct number.
ATP energy released drives anabolic reactions ADP energy used comes from catabolic reactions
Considering the general equation that describes photosynthesis, the rate of the process would be most influenced by the availability of _______ in the atmosphere.
CO2
In order to form lipids, how are fatty acids and glycerol synthesized?
Fatty acid chains are assembled from 2-carbon acetyl groups from the transition step; the precursor to glycerol comes from glycolysis.
In respiring bacteria, how does ATP synthase generate ATP?
It uses the energy released from allowing protons to flow back into the cell to add a phosphate group to ADP.
What are the reduced forms of the electron carriers NAD+ and FAD?
NADH FADH2
The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes
NADH, FADH2
Some members of which of the following groups can use inorganic chemicals such as hydrogen sulfide and ammonia for energy?
Prokaryotes only
Consider the figure showing the relationship between catabolism and anabolism. Which side shows catabolism, and which side shows anabolism?
The left side shows catabolism, and the right side shows anabolism.
The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called
carbon fixation
The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.
catabolism; anabolism
The diagram shows a type of metabolic pathway known as a(n)
cyclical
In oxidative phosphorylation, quinones, cytochromes, and flavoproteins are all
electron
Consider how cells obtain energy to make ATP. The chemical that serves as the electron donor is the
energy; terminal
True or false: The Calvin cycle is a two-step linear pathway that photosynthetic organisms use to fix carbon dioxide
f
In addition to glucose, which of the following organic compounds can serve as energy sources for microbes?
fatty acids proteins lipids disaccharides polysaccharides monosaccharides
The electron transport chain of mitochondria has ______ different protein complexes.
four
In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are ______.
glucose and oxygen
Starch and cellulose are both polymers made up of the monosaccharide
glucose; glycolysis
Fats, the most common simple lipids, are broken down by lipases into their component ______.
glycerol and fatty acids
Lipid synthesis generally requires the components
glycerol; fatty
The three central metabolic pathways that gradually oxidize glucose to CO2 are
glycolysis pentose phosphate TCA
Atoms that are more electronegative than others ______.
have a higher affinity for electrons
In terms of their metabolism, prokaryotes are _______ with respect to compounds they use for energy and _______ in their biosynthetic processes.
highly diverse; remarkably similar
The Calvin cycle ______.
incorporates carbon dioxide into organic compounds
An atom that has a lower affinity (attraction) for electrons than another is described as ______ than the other.
less electronegative
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a
metabolic pathway
The sum total of all chemical reactions in a cell is called
metabolism
The TCA cycle completes the ______ of glucose.
oxidation
Cells use three key metabolic pathways referred to as the central metabolic pathways. These collectively ______.
oxidize glucose to CO2
The central metabolic pathway that generates reducing power in the form of NADPH is the
phosphate
In prokaryotes, the electron transport chain is located in the
plasma, inner
The electron transport chain consists of large protein-complexes embedded in a membrane. These pass electrons from one to the next, while simultaneously pumping
protons
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
regulatory
Proton motive force is ______.
the form of energy that results from the electrochemical gradient established by the electron transport chain
Cells use ATP as the ready and immediate donor of free energy. ATP stands for
adenosine triphosphate
E. coli will preferentially use _____ respiration in the presence of O2, but when O2 is not available, it can switch to ______ respiration if a suitable electron acceptor such as nitrate is present.
aerobic anaerobic
The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______.
after; synthesize organic compounds from CO2
The figure illustrates a type of regulation used by cells to rapidly control certain key enzymes. The arrow labeled "1" points to the
allosteric, active
Some enzymes act with the assistance of a non-protein component. This component is called a
cofactor coenzyme
Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium:
cofactor, coenzyme, cofactor
Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an ______.
energy scource
Proteins that function as biological catalysts are called
enzymes
All of the following accurately describe enzymes EXCEPT ______.
enzymes provide energy to help reactions proceed more rapidly
Which of the following correctly describe cytochromes found in an electron transport chain?
everal different cytochromes exist. Cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center.
Use the following four words to correctly complete the sentence: endergonic, exergonic, anabolism, catabolism."Cells constantly produce ATP during
exergonic catabolism endergonic anabolism
The primary pathway used by many organisms to convert glucose to pyruvate is
glycolosis
What are the two main forms of energy?
kinetic and potential
The enzymes of the tricarboxylic acid cycle are found in the
mitochondrial; cytosol
During cellular metabolism, three key metabolic pathways together gradually _______. These are collectively referred to as the central metabolic pathways.
oxidize glucose to CO2
In oxidation-reduction reactions, or redox reactions, the substance that loses electrons is
oxidized reduced
Each type of the major electron carriers is referred to by two different abbreviations (NAD+/NADH, NADP+/NADPH, and FAD/FADH2).The first of each pair refers to the
oxidized; reduced
The figure depicts oxidation-reduction reactions, which are also known as
redox reactions
Consider the representation of an electron transport chain. O2 is serving as the terminal electron acceptor. Is it being oxidized or reduced?
reduced
Consider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways?
reducing power ATP precursor metabolites
The central metabolic pathways together produce ______.
water and carbon dioxide
Which of the following are important electron carriers for a cell?
NADP+/NADPH NAD+/NADH FAD/FADH2
Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions?
NADPH and ATP
In the representation of an electron transport chain (shown), the terminal electron acceptor is
O2
Proteins are composed of various combinations of usually how many different amino acids?
20
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?
38
Match the type of enzyme inhibition on the left with the example of an inhibitor on the right. Instructions
Competitive inhibition Sulfa drugs Non-competitive inhibition by regulatory molecules Allosteric regulators Non-competitive inhibition by enzyme poisons Mercury
Examples of electron carriers are proteins that contain heme, a molecule that holds an iron in its center. These are called
Cytochromes
True or false: With respect to prokaryotic species such as E. coli, each individual cell will have an electron transport chain made up of the same components.
F
Which of the following are true statements about what happens to glucose inside a cell?
Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. Some glucose might be oxidized to CO2, generating the maximum amount of ATP. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis.
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
Glycolysis
Consider the theoretical maximum ATP yield from the complete oxidation of glucose via aerobic respiration in prokaryotes. Match the relative contribution in terms of ATP (substrate-level phosphorylation plus oxidative phosphorylation) with the correct metabolic component. Instructions
Glycolysis Transition step TCA cycle Total yield of aerobic respiration
Consider the following linear metabolic pathway of a bacterial cell: Starting compound → Intermediate-a → Intermediate-b → End Product. The first two reactions are catalyzed by enzymes A and B, respectively. If a mutant cell arose that was unable to produce enzyme B, what would be the impact on the other components of the pathway?
The cell could still produce intermediate-a but would be unable to produce intermediate-b or the end product.
What is the active site of an enzyme?
The critical site to which a substrate binds by weak forces.
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?
The electron transport chain generates a proton motive force. ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP.
Which of the following is an example of activation energy?
The energy of a small flame used to light the natural gas of a Bunsen burner.
Microorganisms can grow on a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this?
They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis.
In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish?
They capture radiant energy and convert it to chemical energy in the form of ATP.
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?
They will grow aerobically, consume the O2 dissolved in the juice, and then switch to fermenting sugars to yield alcohol.
In the figure, Compound X donates electrons to Compound Y. Which of the following correctly describes this process?
X is oxidized by the reaction, and Y is reduced by the reaction.
The critical site of an enzyme to which a substrate binds by weak forces is called the
actiive site
energy is the energy it takes to start a reaction.
activation
Proteins are hydrolyzed by proteases, enzymes that break the peptide bonds between
amino acid
Nucleotide subunits of DNA and RNA are composed of three units: a 5-carbon sugar, a phosphate group, and a nucleobase. They are initially synthesized ______.
as ribonucleotides that can be converted to deoxyribonucleotides by replacing the 2' hydroxyl group with a hydrogen atom
Which of the following are reasons an organism might use fermentation?
A suitable inorganic terminal electron acceptor is not available. They lack an electron transport chain.
The main energy currency of cells is the molecule called
ATP
When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical things?
ATP, reducing power, precursor metabolites
With respect to their synthesis, how are amino acids typically grouped?
By structurally related families that share common biosynthesis pathways
competitive inhibition non-competitive inhibition by regulatory molecules non-competitive inhibiton by enzyme positions
Inhibitor binds to the active site of the enzyme, blocking access of the substrate Inhibitor reversibly changes the shape of the enzyme so that the substrate can no longer bind to the active site Inhibitor permanently changes the shape of the enzyme, making the enzyme non-functional
Until the optimal temperature is reached, raising the temperature has what effect on the speed of enzymatic reactions?
It increases their rate.
What happens to an organism if it lacks one or more enzymes in a given biosynthetic pathway?
It must have the end product provided from an external source.
Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true?
It often involves the Calvin cycle. In photosynthetic organisms, the process is called the light-independent reactions. It is called carbon fixation.
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?
The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons.
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?
The precursor metabolites from glycerol enter glycolysis; the 2-carbon units from fatty acids are added to coenzyme A and enter the TCA cycle.
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?
Two molecules of pyruvate, each with three carbon atoms.
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to ______.
biosynthesis
Metabolic pathways can be linear,
branched; cyclical
Enzymes are biological ______ that are typically _______.
catalysts; protein
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?
cellular respiration fermentation
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will
denature
This figure shows one half of a redox reaction. Compound X is the electron
donar; acceptor
In addition to four protein complexes, the mitochondrial electron transport chain has two freely-moving ______, ubiquinone and cytochrome c, that serve to ______.
electron carriers; shuttle electrons between the complexes
After a deamination reaction removes the amino group from amino acids, the remaining carbon skeletons are converted into the appropriate
precursor
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
The form of energy that results from the electrochemical gradient established by the electron transport chain is the ______.
proton motive force
The three main types of electron carriers in a typical electron transport chain are
quinones, cytochromes
Enzymes function as biological catalysts, accelerating the conversion of one substance, the
substrate; product
competitive inhibition non-competitive inhibition by regulatory molecules non-competitive inhibiton by enzyme positions
sulfa drugs allosteric regulators mercury
Metabolism is best defined as ______.
sum total of all chemical reactions in a cell
As part of cellular respiration, a membrane-bound enzyme called ATP
synthase
True or false: With respect to the location of the electron transport chain, the inner membrane of mitochondria is analogous to the cytoplasmic membrane of bacterial cells.
t
Certain intermediates of catabolic pathways, called precursor metabolites, are important because ______.
they serve as carbon skeletons from which subunits of macromolecules can be made
