Ch 6 Microbial Metabolism: Fueling Cell Growth (II)
The general group of electron carriers synthesized from the vitamin riboflavin is called
flavoproteins
The electron transport chain of mitochondria has ______ different protein complexes.
four
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
The Calvin cycle ______.
incorporates carbon dioxide into organic compounds
In the representation of an electron transport chain (shown), the terminal electron acceptor is ___ .
oxygen or O2
Consider the representation of an electron transport chain. O2 is serving as the terminal electron acceptor. Is it being oxidized or reduced?
reduced
Flavoproteins are synthesized from the vitamin _______ and play a major role in the _______.
riboflavin; electron transport chain
The ATP generated by fermentation comes from ______.
substrate-level phosphorylation during glycolysis
In prokaryotes, the electron transport chain is located in the _____ membrane, whereas in eukaryotic cells it is in the ___ membrane of mitochondria.
cytoplasmic, plasma, or cell; inner or internal
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
In oxidative phosphorylation, quinones, cytochromes, and flavoproteins are all ____ carriers.
electron or e-
A general group of electron carriers found in electron transport chains is quinones, that ______.
- exist as several types, including ubiquinone and menaquinone - are lipid-soluble organic molecules that move freely in the membrane, transferring electrons between different protein complexes
Ethanol can be produced during fermentation by removing CO2 from pyruvate to generate acetaldehyde, which then serves as the terminal electron acceptor, yielding ethanol. Humans have taken advantage of microorganisms capable of this process in a number of ways. Which of the following are examples of this?
- making biofuels - bread making - wine and beer making
Fats, the most common simple lipids, are broken down by lipases into their component ______.
glycerol and fatty acids
The electrons lost from photosystem II are replaced by electrons derived from a molecule of ____
water
True or false: The Calvin cycle is a two-step linear pathway that photosynthetic organisms use to fix carbon dioxide
False
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.
False
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.
CO2
What microorganisms use a fermentation pathway that results in CO2 and ethanol production?
Saccharomyces species (yeast) and Zymomonas species (bacteria)
As part of cellular respiration, a membrane-bound enzyme called ATP ______ uses energy from a proton-motive force to add a phosphate group to ADP.
synthase
Lipid synthesis generally requires the components _____ and _____ acids.
glycerol; fatty
Purines and pyrimidines are synthesized ______.
in distinctively different manners
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
In non-cyclic photophosphorylation, electrons from _______ are used to replenish the electrons lost from photosystem I.
photosystem II
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 electron transport chain consists of large protein-complexes embedded in a membrane. These pass electrons from one to the next, while simultaneously pumping ____ across the membrane
protons, H+ or H ions
Other than generating some ATP via the substrate-level phosphorylation steps of glycolysis, what critical role do the additional steps of fermentation accomplish?
They consume excess reducing power in order to regenerate NAD+ so that it can accept electrons to keep glycolysis going.
Escherichia coli and Pseudomonas aeruginosa both have an electron transport chain that uses O2 as a terminal electron acceptor, yet E. coli is oxidase negative. Based on this information, it is logical to assume that E. coli ______.
lacks cytochrome c
The reactions that capture radiant energy and convert it into chemical energy in the form of ATP are called the _____-______ reactions.
light dependent
The generation of ATP via photophosphorylation and the generation of reducing power in the form of either NADPH or NADH are accomplished during the ______.
light-dependent reactions of photosynthesis
This picture of a set of stairs best exemplifies the electron ____ ______.
transport chain
The three main types of electron carriers in a typical electron transport chain are ____, ____, and flavoproteins.
quinones; cytochromes
Menaquinone is a quinone used in the electron transport chain of some prokaryotes. It plays an important role for humans and other mammals because it ______.
serves as a source of vitamin K, providing much of the host's requirement via absorption in the intestinal tract
Electron carriers of the electron transport chain are able to move protons across a membrane. They are able to do so because ______.
some accept only hydrogen atoms (proton-electron pairs), whereas others accept only electrons
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.
The lactic acid fermentation pathway is shown here. What statement best explains what is happening in the diagram?
NADH + H+ are donating 2 electrons and 2 protons to pyruvate, an organic terminal electron acceptor, reducing it to lactate.
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
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
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.
In photosynthesis by cyanobacteria and chloroplasts, why is O2 generated?
The process strips electrons from H2O, generating O2.
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.
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.
Cyanobacteria and photosynthetic eukaryotic cells have how many distinct types of photosystems? Multiple choice question.
Two
Consider three major groups of electron carriers found in electron transport chains. Match each description with the correct name
Quinones = Choice Lipid-soluble organic molecules that move freely in the membrane; includes one that serves as a source of vitamin K for humans and other mammals Cytochromes = Choice Proteins that contain heme, a molecule that holds an iron atom in its center Flavoproteins = Choice Proteins that are synthesized from the vitamin riboflavin
Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true?
- In photosynthetic organisms, the process is called the light-independent reactions. - It is called carbon fixation. - It often involves the Calvin cycle.
In terms of their metabolism, prokaryotes are _______ with respect to compounds they use for energy and _______ in their biosynthetic processes.
highly diverse; remarkably similar
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
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.
True
All of the following are essential for an electron transport chain to function EXCEPT
ATP
With respect to their synthesis, how are amino acids typically grouped?
By structurally related families that share common biosynthesis pathways
How does the oxidase test help in bacterial identification?
It detects the activity of cytochrome c oxidase, a component of the electron transport chain of some but not all bacteria.
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.
In prokaryotes, how does the energy yield of aerobic respiration compare to anaerobic respiration?
The energy yield of aerobic respiration is greater than anaerobic respiration.
Why does anaerobic respiration yield less energy than aerobic respiration? Multiple choice question.
The terminal electron acceptors used in anaerobic respiration have lower electron affinities than O2.
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.
Proteins are composed of various combinations of usually how many different amino acids?
20
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.
In an electron transport chain, electron carriers are found in what two general locations?
- Freely moving in the membrane where they can shuttle electrons between protein complexes. - Grouped into large protein complexes that function as proton pumps.
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 ATP
In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are ______.
glucose and oxygen
The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called ____ _____.
carbon fixation
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
Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an ______.
energy source
Photosynthetic organisms use the light-dependent reactions to accomplish which two tasks?
Generate ATP via photophosphorylation; generate reducing power
Lactic acid is a common fermentation product of which of the following types of cells?
Gram-positive lactic acid bacteria
Some members of which of the following groups can use inorganic chemicals such as hydrogen sulfide and ammonia for energy?
Prokaryotes only
The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______.
after; synthesize organic compounds from CO2
Proteins are hydrolyzed by proteases, enzymes that break the peptide bonds between ____ _____subunits.
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
Lactic acid production by fermenting microorganisms has many benefits for humans, but also can cause some problems. Which of the following are examples of these advantages and disadvantages?
- Results in food spoilage. - Contributes to tooth decay. - Production of pickles and cured sausages. - Creating flavor and texture of yogurt and certain cheeses.
Which of the following correctly describe cytochromes found in an electron transport chain?
- Several different cytochromes exist. - Cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center
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.
In addition to glucose, which of the following organic compounds can serve as energy sources for microbes?
- polysaccharides - disaccharides - proteins - fatty acids - monosaccharides - lipids
Examples of electron carriers are proteins that contain heme, a molecule that holds an iron in its center. These are called ____.
cytochromes
This diagram depicts the production of ethanol from pyruvate via fermentation. What best explains the mechanism?
CO2 removal converts pyruvate to the terminal electron acceptor acetaldehyde, which receives 2 electrons and protons from NADH + H+, making ethanol.
