Micro 200a- Midterm 2 MC Q's Flashcards
The sum of all biosynthetic reactions in a cell is known as
anabolism
Based on the functional roles of phosphate in various microbial metabolisms, deduce which compounds phosphate exists as in microorganisms
both organic and inorganic compounds
Which of the following would be used by a chemoorganotroph for energy? A) C2H3O2- B) H2 C) CO2 D) H+
C2H3O2-
Which of the following statements is FALSE?
A) Most bacteria are capable of using ammonia as their sole nitrogen source.
B) Some bacteria are able to use nitrates or nitrogen gas as their nitrogen source.
C) Most available nitrogen is in organic forms.
D) Nitrogen is a major component of proteins and nucleic acids.
Most available nitrogen is in organic forms
All microorganisms require
phosphorus, selenium, and sulfur
Based on your understanding of metabolism, generalize when an enzyme’s rate of activity can be changed.
after enzyme production
The change in Gibbs free energy for a particular reaction is MOST useful in determining
whether there will be a requirement or production of energy.
Which is an example of a micronutrient? A) arginine B) inorganic phosphorous C) iron D) vitamin B12
iron
Aseptic technique refers to
a series of practices to avoid contamination.
To ensure growth of a newly discovered bacterium with unknown nutritional requirements, it would be best to begin with a ________ medium rather than a ________ medium.
complex / minimal
If ΔG0’ is negative, the reaction is
exergonic and energy will be released.
Activation energy is the energy
required to transform all reactants into their reactive state.
A catalyst
changes the rate of the reaction but does not change the end amount of products.
The portion of an enzyme to which substrates bind is referred to as the
active site.
What is the difference between a coenzyme and a prosthetic group?
Coenzymes are weakly bound whereas prosthetic groups are strongly bound to their respective enzymes.
If an oxidation reaction occurs
simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.
A chemoorganotroph and a chemolithotroph in the same environment would NOT compete for
carbon.
A chemoorganotroph and a photoautotroph in the same environment would NOT compete for
carbon and oxygen.
The Embden-Meyerhof-Parnas pathway is another name for
glycolysis.
The net gain of ATP per molecule of glucose fermented is
2.
Fermentation has a relatively low ATP yield compared to aerobic respiration because
oxidative phosphorylation yields a lot of ATP.
From the standpoint of the microorganism, in glycolysis the crucial product is
ATP; the fermentation products are waste products.
In aerobic respiration, the final electron acceptor is
oxygen.
The rising of bread dough is the result of
carbon dioxide produced by fermentation.
Which feature of anaerobic and aerobic respiration is different between the two catabolic strategies?
electron acceptor
For a carbon source, chemoorganotrophs generally use compounds such as
acetate, succinate, and glucose.
How does the proton motive force lead to production of ATP?
Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.
Five-carbon sugars are used in the
biosynthesis of DNA and RNA.
Most of the carbon in amino acid biosynthesis comes from
citric acid cycle intermediates and glycolysis products.
T/F: A bacterial isolate that grows better on a nutrient agar plate supplemented with amino acids but still grows in a nutrient agar plate lacking amino acids suggests amino acids are trace nutrients for the isolate.
False.
T/F: In a given chemical reaction, if the free energy of formation is known for all of the reactants and each of the products, the change in free energy can be calculated for the reaction.
True
T/F: Free-energy calculations are dependent on the rates of the reactions.
False
T/F: With respect to nitrogen utilization, relatively few bacteria can use NH3 whereas many more can make use of N2.
False
T/F: If a substance is reduced, it gains electrons.
True.
T/F: In substrate-level phosphorylation, ATP storage is depleted during the steps in catabolism of the fermentable compounds.
False
T/F: Catabolic pathways are essential for microorganisms to obtain energy, because biosynthetic reactions for cellular growth generally require energy input.
True
T/F: Many defined growth media that support microbial growth lack malonate, which is an important precursor for biosynthesis of lipid membranes. Based on this, we can infer cells also must have a metabolic pathway to generate malonate from other compounds.
True
T/F: The net result of electron transport is the generation of a pH gradient and an electrochemical potential across the membrane.
True
Why do eukaryotes have organelles?
prevents interference between competing pathways
An organotrophic organism is distinguished by
obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic.
Which of the following is always true for enzymes?
catalyze exergonic reactions
Which of the following is always true of lithotrophs?
utilize inorganic molecules as an electron source
What do chemotrophs utilize as an electron source?
reduced compounds
What is used to define the change in free energy of a reaction taking place in a living cell?
ΔG
What type of agar can be used to detect hemolysis?
blood agar
In general, what is the relationship between heat and the efficiency of microbial control methods?
decreasing temperature decreases effectiveness
Generally, what environment will a facultative anaerobe grow best in?
aerobic environment
Which of the following organisms would you be most likely to encounter in a human duodenum, which is the compartment of the gut immediately following the stomach?
facultative anaerobe, acidophile, mesophile
Which of the following can be safely used to disinfect skin?
quaternary ammonium compounds
Which of the following statements accurately describes facilitated diffusion?
facilitated diffusion requires a protein to transport molecules
When might you utilize a differential supportive media that contains bile salts?
to enrich the number of E. coli cells in a mixture of Gram +ve and Gram –ve organisms
A soil organism gets its electrons and energy from organic carbon sources. What classification best describes this organism?
chemoorganotroph
You have developed a media that contains the sugar lactose as the sole carbon source . There are no unknown extracts, but there is a pH indicator in the media to identify products of lactose fermentation. With the information provided, how would you describe this media?
selective and differential
Which of the following about redox pairs is true?
the reducing agent is oxidized during the reaction
Which of the following lists is arranged in order, from lowest level of cleanliness to highest?
untreated, sanitized, disinfected
What adaptations do cells have to survive in high osmosis conditions?
compatible solutes
Which of the following statements about oxygen is true?
can be converted to toxic products in the cell
Which of the following lists is composed entirely of growth factors?
amino acids, vitamins
Which of the following statements about protists are true?
may be flagellated
On a growth curve, the four stages of growth, in order are:
lag phase, exponential phase, stationary phase, death phase
What is the difference between soap and antibacterial soap?
only antibacterial soap targets specific enzymes
An aquatic microbe utilizes light energy to convert CO2 into sugars. What classification best describes this organism?
photoautotroph
The lethal target of heavy metals is:
protein
Where are antiseptics typically used?
surface of living tissue
During feedback inhibition of metabolic pathways, why does the inhibitor generally bind allosterically?
end product of a pathway must be structurally different from the starting product and can’t bind the active site
What is one advantage and one disadvantage of measuring growth by plate counts?
disadvantage – time consuming / advantage - only counts living cells
Which of the following is NOT true of a biofilm?
biofilms maintain a homogeneous environment for bacteria
Cyanobacteria typically use CO2 as the primary carbon source. Such organisms would be:
autotrophs
Which of the following would be associated with most of the ATP produced by cyanobacteria growing in the light?
Photophosphorylation
In the Citric Acid Cycle, what side rxn is associated with:
Pyruvate+CoA→ Acetyl-CoA+CO2
Isocitrate→α-Ketoglutarate+CO2
α-Ketoglutarate+CoA→Succinyl-CoA
Malate→Oxaloacetate
NAD+ → NADH
In the Citric Acid Cycle, what side rxn is associated with:
Succinate→Fumarate
FAD → FADH2
In the Citric Acid Cycle, what side rxn is associated with:
Succinyl-CoA → Succinate+CoA
GDP+Pi → GTP
In the Citric Acid Cycle, what side rxn is associated with:
Acetyl-CoA+Oxaloacetate → Citrate+CoA
Fumarate → Malate
No side reaction
Trace elements are found in bacterial cells in very small amounts because they __________.
function only in a limited set of enzymes and cofactors
Which of the following statements is FALSE?
- Most available nitrogen is in organic forms.
- Some bacteria are able to use nitrates or nitrogen gas as their nitrogen source.
- Most bacteria are capable of using ammonia as their sole nitrogen source.
- Nitrogen is a major component of proteins and nucleic acids.
Most available nitrogen is in organic forms.
All microorganisms require
phosphorus, selenium, and sulfur.
Which element functions BOTH as an enzyme cofactor and as a stabilizer of ribosomes and nucleic acids?
magnesium
Which is an example of a micronutrient?iron
arginine
vitamin B12
inorganic phosphorous
iron
The class of macromolecules in microorganisms that contributes MOST to biomass is
proteins.
In aerobic respiration, the final electron acceptor is
oxygen.
All of the following are non-protein electron carriers EXCEPT
FMNH2.
FADH2.
quinones.
cytochromes.
cytochromes.
When culturing a chemoorganoheterophic bacterium, what outcome is LEAST likely to occur if ammonia and phosphate are provided at equal concentrations?
Cells require much less P to grow than N, so extra P will be used for ATP synthesis and result in a faster growth rate.
Organic micronutrients are commonly called __________.
growth factors
T/F: A bacterial isolate that grows better on a nutrient agar plate supplemented with amino acids but still grows in a nutrient agar plate lacking amino acids suggests amino acids are trace nutrients for the isolate.
False
T/F: Magnesium is not considered a growth factor for microorganisms, because growth factors are always organic compounds.
True
T/F: Cells require iron supplemented in their growth medium as a trace metal, because it is consumed by quinones during electron transport for ATP production.
False
T/F: During the electron transport process, protons and electrons become physically separated in the cell membrane.
True
Fuel for cellular respiration:
Which of the following molecules is broken down in cellular respiration, providing fuel for the cell?
glucose
Energy for cell work:
Which energy-rich molecule directly powers cell work?
ATP
Which of the following would NOT be required to grow an autotroph?
elements
potassium phosphate
glucose
water
glucose
A nurse takes a urine sample from a patient suspected of having contracted a urinary tract infection. The nurse uses careful aseptic technique in collecting the sample. Which is NOT a reason for using aseptic technique in this situation?
to get as many organisms as possible to grow in the culture medium
Aseptic technique refers to
a series of practices to avoid contamination.
To ensure growth of a newly discovered bacterium with unknown nutritional requirements, it would be best to begin with a ________ medium rather than a ________ medium.
complex / minimal
Explain why you would use selective media instead of differential media to grow an organism.
You only want to determine the cell wall type, not any biochemical characteristics.
organisms obtain their energy from different types of metabolic pathways
chemicals= chemotrophs light= phototrophs
organisms obtain their energy from different types of metabolic pathways
chemicals= chemotrophs
light= phototrophs
types of molecules chemotrophic organisms obtain their energy from
organic chemicals= chemoorganotrophs
inorganic chemicals= chemolithotrophs
chemoorganotrophs organic chemicals=
glucose, acetate, etc.
chemolithotrophs inorganic chemicals=
H2, H2S, Fe 2+, NH4 +, etc.
lithotrophs electron source:
H2 + O2 → H2O
organotrophs electron source:
glucose + O2 → CO2 + H2O
A defined culture medium must supply all of the nutrients an organism needs, including essential biochemicals that the cell cannot synthesize. Based on the following recipe, this defined medium could support the growth of certain members of what group? Recipe: 7 g of K2HPO4; 2 g of KH2PO4; 1g of (NH4)2SO4; 0.1g of MgSO4; 0.02g of CaCl2; 10g of glucose; trace elements mix; 1000mL of distilled water; adjust to pH 7.
chemoorganotroph
Which of the following would be used by a chemoorganotroph for energy?
CO2
H+
H2
C2H3O2-
C2H3O2-
A chemoorganotroph and a chemolithotroph in the same environment would NOT compete for
carbon.
A chemoorganotroph and a photoautotroph in the same environment would NOT compete for
carbon and oxygen.
For a carbon source, chemoorganotrophs generally use compounds such as
acetate, succinate, and glucose.
Which statement below demonstrates why the majority of organisms are heterotrophs?
The majority of organisms obtain their carbon from organic sources.
In metabolism, energy that is not used
is given off as heat.
The reactions involved in producing larger compounds from smaller compounds is called
anabolism.
Where does the energy required for anabolic reactions come from?
Catabolic reactions
The use of amino acids to make proteins
is an example of anabolism.
According to the animation, oxidative phosphorylation
is a catabolic process.
According to the animation, the reactions that occur between glucose and pyruvic acid
can either be anabolic or catabolic.
To calculate the free energy (ΔG0′) of a reaction, you can subtract the free energies of formation (Gf0) of the reactants from those of the products. Given the following data, what will be true of this reaction? C6H12O6 + O2 → CO2 + H2O Gf0 : -917.3 0 -394.4 -237.2
The reaction will be exergonic.
The change in Gibbs free energy for a particular reaction is MOST useful in determining
whether there will be a requirement or production of energy.
If ΔG0’ is negative, the reaction is
exergonic and energy will be released.
T/F: Free-energy calculations are dependent on the rates of the reactions.
False
Properly label the steps that occur as an enzyme catalyzes a chemical reaction.
- enzyme active site is filled by substrate
- enzyme-substrate complex forms
- catalytic cycle is ready to begin again
- the bond in the substrate is strained
- release of products
The role of an enzyme includes all EXCEPT which of the following?
- reducing the rate of a reaction to allow for better control
- straining chemical bonds in a substrate so that they break easier
- lowering the activation energy of a reaction
- binding only one specific substrate to the enzyme active site
reducing the rate of a reaction to allow for better control
Based on your understanding of metabolism, generalize when an enzyme’s rate of activity can be changed.
after enzyme production
Activation energy is the energy
required to transform all reactants into their reactive state.
A catalyst
changes the rate of the reaction but does not change the end amount of products.
The portion of an enzyme to which substrates bind is referred to as the
active site.
T/F: In a given chemical reaction, if the free energy of formation is known for all of the reactants and each of the products, the change in free energy can be calculated for the reaction.
True
Why do all enzymatic reactions need activation energy?
Energy is required to disrupt a substrate’s stable electron configuration.
What is meant by the statement “Enzymes are biological catalysts”?
Enzymes speed up the chemical reactions in living cells.
Why are enzymes important to biological systems?
Enzymes decrease the amount of activation energy required for chemical reactions to occur.
The reduction potential (E0′) of a substance reflects its tendency to donate or accept electrons. The larger the difference (ΔE0′) between the reduction potentials of the electron donor and the electron acceptor, __________.
the greater the change in free energy (ΔG0′), and the greater the energy released
If an oxidation reaction occurs
simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.
The function of NAD+/NADH in the cell is best described as __________.
a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between dissimilar compounds
T/F: If a substance is reduced, it gains electrons.
True
A reaction that involves the transfer of electrons from one molecule to another is referred to as
a redox reaction.
During an oxidation reaction,
the donor molecule loses an electron and becomes oxidized.
Why is reduction the term used to describe the gain of an electron?
The electron acceptor’s net charge decreases.
Which of the following statements regarding redox reactions is true?
- No metabolic reactions are redox reactions.
- Redox reactions must either be oxidizing reactions or reducing reactions.
- Redox reactions are only seen in the electron transport chain.
- Redox reactions involve an oxidation reaction coupled with a reduction reaction.
Redox reactions involve an oxidation reaction coupled with a reduction reaction.
T/F: Due to the number of phosphate groups, ATP has approximately three times more energy stored than AMP, and ADP has approximately two-thirds the energy stored of ATP.
False
At the doctor’s office, the doctor drains the abscess and takes a sample for culturing. She also prescribes some broad-spectrum antibiotics to treat the obvious infection. A couple days later, the doctor tells Sam that his wound contained a number of bacteria including Pasteurella multocida. When the dog bit Sam’s arm P. multocida entered the wound and started to establish an infection. In order to do so, the bacteria have to grow, which requires energy. One of the most common energy sources used by bacteria is glucose. Why is glucose such a good source of energy for bacteria?
Glucose is a highly reduced compound, containing many carbon-hydrogen bonds and a lot of potential energy.
The P. multocida that are growing within Sam’s abscess are breaking glucose down via glycolysis in order to obtain energy. This process occurs via a series of enzymatic reactions. During a chemical reaction, an enzyme functions as a biological catalyst and lowers the activation energy. How does an enzyme lower the activation energy of a reaction?
The enzyme increases the effectiveness of reactant collisions thereby increasing the number of reactant molecules that reach activation energy.
During the infection, there are many different environments that P. multocida will encounter. In order to cause an infection like the one in Sam’s forearm, P. multocida must regulate its metabolic pathways in order to adapt to the changing environments. The process of glycolysis is regulated at several steps by allosteric inhibition. Which of the following are features of allosteric inhibition?
- Allosteric inhibition can be irreversible.
- Allosteric inhibition can be reversed.
- The allosteric inhibitor binds to a site distinct from the active site resulting in decreased affinity of the enzyme for the substrate.
Arrange the components of the electron transport chain in order from least electronegative to most electronegative thereby indicating the path of electrons through the electron transport chain.
- NADH dehydrogenase
- Coenzyme Q
- Cytochrome b-c1 complex
- Cytochrome c
- Cytochrome oxidase complex
- O2
One of the environmental changes that P. multocida encounters during infection is the limitation of nutrients and oxygen. One of the changes that P. multocida (a facultative anaerobe) makes in this environment is to switch to anaerobic metabolism. Predict which of the following is most likely to occur as a result of the switch from aerobic to anaerobic metabolism.
The organisms will grow more slowly because they will produce less ATP compared to aerobic metabolism.
Fermentation occurs when there is no usable external electron acceptor (like O2) available for respiration. The fermentation products are made following glycolysis as a result of reactions that __________.
oxidize NADH so that NAD+ can be reused again in glycolysis
The Embden-Meyerhof-Parnas pathway is another name for
glycolysis.
The net gain of ATP per molecule of glucose fermented is
2.
Which of the following is a common energy storage polymer in microorganisms?
glycogen
Fermentation has a relatively low ATP yield compared to aerobic respiration because
oxidative phosphorylation yields a lot of ATP.
From the standpoint of the microorganism, in glycolysis the crucial product is
ATP; the fermentation products are waste products.
Applying your knowledge of metabolism, glycolysis starts with one molecule of glucose (6C) and produces a net total of __________.
two pyruvates; 2 NADH; 2 ATP
T/F: In substrate-level phosphorylation, ATP storage is depleted during the steps in catabolism of the fermentable compounds.
False
Why is ATP required for glycolysis?
ATP makes it easier to break apart glucose into two three-carbon molecules.
Glycolysis literally means
sugar splitting.
How many net ATPs can be made from one molecule of glucose in glycolysis?
Two
What carbon molecules remain at the end of glycolysis?
Pyruvic acid
Which of the following statements about glycolysis is true?
- Glycolysis is the main source of NADH in the cell.
- All cells perform glycolysis.
- Glycolysis is also called the Embden-Meyerhof pathway.
- Glycolysis produces glucose.
Glycolysis is also called the Embden-Meyerhof pathway.
Glycolysis produces energy in which form?
NADH and ATP
Which step is the step for which glycolysis is named?
Fourth
What is meant by substrate-level phosphorylation?
Production of ATP by transferring phosphates directly from metabolic products to ADP
What is the driving force of energy production in steps 6 and 7 of Gylcolysis?
The oxidation of three-carbon compounds (ADP to ATP)
What is the net production of ATP in glycolysis?
2 ATP
Distinguish how fermentation and respiration differ.
Fermentation forms organic acids and takes place in the absence of oxygen, while respiration forms water and carbon dioxide in the presence of oxygen.
Which of the following statements about fermentation is true?
- It allows the electron transport chain to continue in the absence of oxygen.
- It is an alternative way to return electron carriers to their oxidized state.
- It provides additional protons to allow the electron transport chain to continue.
- It is an alternative way for a cell to produce oxygen.
It is an alternative way to return electron carriers to their oxidized state.
What is the role of pyruvic acid in fermentation?
It takes the electrons from NADH, oxidizing it back into NAD+.
What is the fate of the NAD+ newly regenerated by fermentation?
It returns to glycolysis to pick up more electrons.
Which of the following is an acid produced by fermentation?
Lactic acid and propionic acid
What is the intermediate product formed by pyruvic acid during alcoholic fermentation?
Acetaldehyde
Electron carriers used in electron transport chains are always found in membranes. Which one of the following statements is NOT a reason why electron transport chains are found in membranes?
- so that the electron carriers can be oriented within the membrane such that protons are passed from one side of the membrane to the other
- so that they can efficiently pass electrons in sequence from the carriers with the more negative reduction potentials to those with the more positive reduction potentials
- so that they can transport NADH out of the cell to the periplasm
- So that electron-only carriers can be arranged to alternate with electron-plus-proton carriers in the chain.
so that they can transport NADH out of the cell to the periplasm
During electron transport reactions,
OH- accumulates on the inside of the membrane while H+ accumulates on the outside.
The rising of bread dough is the result of
carbon dioxide produced by fermentation.
How does the proton motive force lead to production of ATP?
Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.
Hypothetically, if electron pools existed in sufficient numbers for enzymes to use in metabolic reactions,
most metabolic pathways for both anabolism and catabolism would have to be rewritten.
The proton motive force (PMF) is driven by __________.
the difference in charge across the plasma membrane with protons outside the membrane
T/F: Depending on the particular metabolism of a bacterium, electron transport can be used to energize and rotate ATP synthase.
False
T/F: The terminating step of moving electrons onto oxygen releases additional ATP during aerobic metabolism not made during anaerobic growth.
False
T/F: The proton motive force is most often generated by splitting of H2.
False
T/F: In electron transport systems, the electron carriers are membrane associated.
True
T/F: The net result of electron transport is the generation of a pH gradient and an electrochemical potential across the membrane.
True
Electron Transport Chain: Factors Affecting ATP Yield
Why does lack of oxygen result in the halt of ATP synthesis?
The chain shuts down and can no longer pump hydrogen ions across the membrane, and the proton gradient cannot be maintained.
Why might some cells uncouple the electron transport chain?
Cells can use the energy from the proton gradient for functions other than producing ATP, such as heat generation.
How does cyanide poisoning result in the decrease of ATP production?
Cyanide permanently reduces cytochrome a3, preventing other components to change into the oxidized state. This causes the proton gradient to break down, stopping ATP synthesis.
Which of the following situations does not result in a breakdown of the proton gradient?
Uncoupling proteins
Where would you expect to find electron transport chains in a prokaryote?
Along the plasma membrane
According to the animation, which compounds provide electrons to the ETC system?
NADH and FADH2
According to the animation, what does oxygen get reduced to at the end of the electron transport chain?
Water
According to the animation, what does the electron transport chain do to the concentration of hydrogen ions (protons)?
The concentration of protons is higher outside the membrane than inside.
The process of generating ATP using a proton gradient is referred to as
chemiosmosis.
Why does FADH2 yield less ATP than NADH?
FADH2 electrons enter the electron transport chain at a lower energy level.
Which of the following can be used as a final electron acceptor for aerobic respiration?
Molecular oxygen
What is one difference between ubiquinones and cytochromes?
Ubiquinones are not made of protein; cytochromes are
How does the proton gradient help ATP synthase to make ATP?
Protons move from outside the membrane to inside the membrane.
Iron is considered an essential element for many bacteria. Based on the animation, how would lack of iron affect energy production of a bacterium?
Lack of iron would mean lack of heme, and thus lower amounts of functioning cytochrome proteins. This would mean lower energy yields.
If the citric acid cycle was interrupted after the reaction that forms citrate, predict how this would affect the total amount of ATP generated per glucose molecule.
The amount of ATP would be reduced from a total of 38 ATP to 14 ATP.
T/F: Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.
True
T/F: Catabolic pathways are essential for microorganisms to obtain energy, because biosynthetic reactions for cellular growth generally require energy input.
True
Krebs Cycle:
What occurs at the bridge step?
Decarboxylation of pyruvic acid
Based on the animation, how many electron carriers are reduced in the Krebs cycle only?
Four
Krebs Cycle:
What is the function of GTP?
An energy carrier
What is the fate of metabolites during respiration?
They are oxidized completely to carbon dioxide and water.
Which of the following is needed as a reactant for the first step of the citric acid cycle?
Oxaloacetic acid
Krebs Cycle:
Where does the energy come from to power the formation of GTP?
Succinyl CoA
Krebs Cycle:
Which step involves the release of carbon dioxide?
The third and fourth steps
Krebs Cycle:
How many molecules of ATP can be generated from one molecule of NADH?
3
Which step(s) of the Krebs cycle does (do) not produce any usable energy?
The second and seventh steps
What is the correct general equation for cellular respiration?
C6H12O6(glucose) + 6O2 → 6CO2 + 6H2O + ATP energy
the correct sequence of steps as energy is extracted from glucose during cellular respiration.
glycolysis → acetyl CoA → citric acid cycle → electron transport chain
Which of the following processes takes place in the cytosol of a eukaryotic cell?
glycolysis
In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
mitochondrion
statement describes glycolysis?
This process splits glucose in half and produces 2 ATPs for each glucose.
statement describes the citric acid cycle?
This process produces some ATP and carbon dioxide in the mitochondrion.
statement describes the electron transport chain?
This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration.
Which of the following equations represents photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
In which of the following organelles does photosynthesis take place?
Chloroplast
What connects the two photosystems in the light reactions?
An electron transport chain
What two molecules are produced by the light reactions and used to power the Calvin cycle?
ATP and NADPH
What provides electrons for the light reactions?
H2O
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
Carbon dioxide (CO2)
What transports electrons from the light reactions to the Calvin cycle?
NADPH
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
thylakoids; stroma
The sum of all biosynthetic reactions in a cell is known as
anabolism.
Which feature of anaerobic and aerobic respiration is different between the two catabolic strategies?
electron acceptor
Which metabolic strategy does NOT utilize the proton motive force?
fermentation
How is anaerobic respiration different from aerobic respiration?
The terminal electron acceptor in anaerobic respiration is not oxygen
Gluconeogenesis is the process of synthesizing __________.
glucose from other compounds
Which two metabolic processes are MOST dissimilar?
glycolysis and gluconeogenesis
One example of an electron acceptor that can be used in anaerobic respiration is
nitrate.
Most of the carbon in amino acid biosynthesis comes from
citric acid cycle intermediates and glycolysis products.
T/F: With respect to nitrogen utilization, relatively few bacteria can use NH3 whereas many more can make use of N2.
False
B. subtilis cell shape
The L-form B. subtilis bacteria described in the introductory passage have a spherical shape and pattern of growth that is very different from non-mutant B. subtilis, which is a rod-shaped bacterium. What best explains the difference in appearance and shape?
A sphere is the most energetically favorable shape for a cell.
Cell membranes and temperature:
Hyperthermophiles are organisms that thrive at extremely high temperatures. What sorts of specializations might they have to survive in such high temperatures?
- cell membranes with long chain fatty acids
- monolayer membranes that link one side to the other for stability
- extremely heat stable proteins that function best at high temperatures
- increased use of isoprene units instead of fatty acids
Osmotic conditions:
- a hypersaline environment
- an environment that is hypertonic to the inside of the cell
Desiccation
Osmotic conditions:
- an environment that is isotonic to the inside of the cell
- an isotonic environment containing penicillin
Growth and survival
Osmotic conditions:
- an environment that is hypotonic to the inside of the cell
- a liquid culture of distilled water with minimal added materials
Lysis
Microbial control using temperature
Microbes are found at a wide range of temperatures, from the cold in the Antarctic to hot springs like those at Yellowstone National Park. In the introductory passage, B. subtilis is discussed because it has been used as a model organism. B. subtilis is a bacterium normally found in the human gut and can sometimes cause disease. An autoclave is often used at a temperature of 121°C, which is close to the maximum temperature for most Archaea (122°C). What is likely to be an optimal temperature for the growth of B. subtilis?
- The optimal temperature for the growth of B. subtilis is 36-38°C.
- B. subtilis is considered a mesophile.
What results when a single bacterium reproduces?
Two genetically identical daughter cells
If you begin with six cells, how many cells would you have after three rounds of division?
48 cells
Which of the following is NOT a step in bacterial cell division?
Disappearance of nuclear envelope
Splitting apart of two new daughter cells
Cell elongation
Replication of the genetic material
Disappearance of nuclear envelope
Which step of binary fission is the reason for genetically identical daughter cells?
Replication of the bacterial chromosome
What enables the copied chromosomes to separate during binary fission?
The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes.
How long does it take for the daughter cells from one round of replication to replicate themselves?
No time is required – they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.
Put the following steps of bacterial replication in the correct order, starting from a parent cell.
Cell elongation
Septum formation
Chromosome replication
Separation of daughter cells
Chromosome replication
Cell elongation
Septum formation
Separation of daughter cells
What would happen if the septum did not form during binary fission?
The parent cell would now have two copies of the chromosome.
Starting with three cells, how many cells would result from three rounds of replication?
24
A typical bacterial growth curve exhibits distinct phases. It is important to know which phases occur when and what is occurring during each phase.
lag- exponential- stationary- death phase
Place the labels for each step in the spread- plate viable count methods in the correct order
- small portion of sample is pipetted onto agar
- sterile glass is used to evenly spread sample
- incubation
Place the labels for each step in the pour-plate viable count methods in the correct order
- sample is pipetted into sterile empty plate
- sterile medium is added and mixed with sample
- solidification and incubation
Correctly identify the term used to characterize each microbial group based on ideal growth temperature range.
4 degrees
ex. Polaromonas vacuolata
Psychrophile
Correctly identify the term used to characterize each microbial group based on ideal growth temperature range.
39 degrees
ex. E coli
Mesophile
Correctly identify the term used to characterize each microbial group based on ideal growth temperature range.
60 degrees
ex. Geobacillus
Thermophile
Correctly identify the term used to characterize each microbial group based on ideal growth temperature range.
88-106 degrees
ex. (88) Thermococcus celer
(106) Pyrolobus fumarii
Hyperthermophile
Which of the following is/are transferred to daughter cells during cell division?
chromosome, proteins, and all other cellular constituents
The process by which two cells arise from one is known as
binary fission
The time interval required for the formation of two cells from one is called the
generation time.
Enumerating cells in a biofilm is especially challenging for
microscopic direct county, measuring turbidity, and viability counts with spread plating.
Which of the following methods to enumerate cells often requires specialized staining to observe non-pigmented bacteria?
microscopy
The partition that is a result of the inward growth of the cytoplasmic membrane and cell wall from opposing directions is known as the
septum.
One laboratory group repeated the same experiment described by others with the identical bacterial isolate and the same growth medium and conditions used but were unable to achieve the same O.D. at 600 nm. What is the LEAST likely cause for this discrepancy of turbidity measured?
The two labs varied with 1000 m elevation and did not consider the influence of pressure.
T/F: Microbial growth is generally described as the increased number of cells rather than the expanding size of an individual microbial cell.
True
T/F: Generation of new bacillus-shaped cells starts with one cell elongating and terminates when split into two separate bacilli.
True
T/F: In fast-growing Escherichia coli cells, multiple replication forks of genomic DNA allows binary fission to occur before the genome has been fully duplicated.
False
Both lysozyme and penicillin disrupt the bacterial cell wall peptidoglycan, leading to cell lysis. However, their mechanisms of action are different, resulting in the fact that __________.
penicillin kills only growing cells
An antibiotic that increased the activity of ________ would likely result in cell death.
autolysin
T/F: During elongation of a cell during binary fission, small gaps caused by transglycosylases are formed before cell membrane precursors can be inserted.
False
To determine the specific growth rate of a bacterial population, it is essential to know
cell concentrations at varied time points.
In a batch culture, bacterial cultures typically exhibit four different phases of growth. In which phase are the cells rapidly synthesizing proteins, but cell numbers are not changing?
lag phase
The time between inoculation and the beginning of growth is usually called the
lag phase
Optical density and viable cell concentration are LEAST proportional to each other during
death phase.
A closed system, used for bacterial growth, where nothing is added and nothing is removed is called __________.
a batch culture
what occurs in the stationary phase of bacterial growth?
cryptic growth, where the number of new cells equals the number of dying cells
T/F: The duration of logarithmic growth would increase if bacterial cells divided into three equal daughter cells rather than two.
False
T/F: The lag phase does NOT occur if all the cells in the culture are viable.
False
T/F: The rates of exponential growth (in the exponential phase) vary greatly according to the bacterial species as well as the bioavailable nutrients.
True
T/F: In both lag and stationary phase, there is no net increase or decrease in viable cells.
True
The death phase applies to individual cells rather than populations.
False
A microbial ecologist wants to study a bacterium that is adapted to growth in lake water containing very low nutrient concentrations. Assuming that a suitable growth medium is available for this organism, which type of culture would be best to use for growing this organism in the lab?
a chemostat using a low-nutrient medium
In a culture grown in a chemostat (continuous culture), the best way to increase the yield of bacteria (numbers of cells per mL) would be to __________.
increase the concentration of nutrients in the medium
Cell density in a chemostat is controlled by
the concentration of the limiting nutrient.
By controlling the concentration of nutrients added into a chemostat continuously, cells can constantly be maintained at
log or stationary growth phase.
Growing bacteria that degrade an environmental pollutant, which is also toxic to the cells at artificially high concentrations, might require ________ to obtain a sufficient population for biochemistry studies.
the use of a chemostat
T/F: In a chemostat, growth rate and growth yield can be controlled independently.
True
T/F: Heterotrophic bacteria will run out of organic growth substrates in batch cultures but chemostats can provide constant nutrient source for them to grow. Chemostats for photoautotrophic bacteria are not necessary to maintain them at a constant growth phase because a light can artificially be turned on constantly.
False
A student has a pure culture of bacteria growing in a flask and wants to know how many living cells are in the culture at a given time. Which method should she employ to get an estimate?
plate counts
T/F: Direct microscope counting of stained cells is an accurate method for calculating the exact number of cells in a sample.
True
T/F: Counting chambers are used for estimating the number of cells present in a liquid culture.
True
To determine viable cell counts of a heat-sensitive bacterial isolate, which cell counting method would be best to AVOID?
pour-plate method
An agar plate for counting colonies and maximizing statistical validity should ideally contain
30 to 300 colonies.
The number of colonies obtained in a plate count does NOT depend on the
size of the colonies.
T/F: For most purposes of studying bacterial isolates, viable counting usually gives accurate information about the number of active cells present in a culture volume.
True
T/F: By using a stain targeting living cells only, microscopy would be a better approach to enumerate the number of living cells in a soil sample compared to viability counts of serially diluted soil.
True
T/F: When viable cell concentrations are too high to count on an agar medium, it is most common to use larger sized plates to increase the surface area for counting the colonies.
False
In mesophiles, growth rates increase gradually as the temperature is increased, until the optimum growth temperature for the organism is reached. If the temperature is increased beyond the optimum, __________.
growth rates decline rapidly as the temperature increases
Bacteria that are able to grow in humans and cause disease have likely evolved to be
mesophiles.
Most mesophilic organisms can grow in a temperature range of
20-40°C.
A microbe growing in a refrigerator is likely
psychrotolerant or psychrophilic.
T/F: One reason food is refrigerated to control microbial growth is because irreversible cell damage is more likely to occur at low rather than high temperatures.
False
T/F: The optimum temperature is usually closer to the minimum temperature than the maximum temperature.
False
Relative to enzymes in mesophilic microorganisms, which of the following is NOT characteristic of enzymes in psychrophiles?
decreased alpha helices
T/F: A bacterium such as a snow alga that is able to survive a cold temperature is called a psychrophile.
False
Which of these statements is/are TRUE?
- Nonphototrophic organisms are able to grow at higher temperatures than phototrophic organisms.
- The most thermophilic prokaryotes are species of Archaea.
- In general, prokaryotic organisms can grow at higher temperatures than eukaryotic organisms.
- All of the statements are true.
All of the statements are true.
statement shows which adaptations are necessary for hyperthermophilic proteins to stay functional at temperatures above 80°C?
Hyperthermophiles have increased ionic bonds to stabilize the proteins.
T/F: Some microbes can grow in boiling water.
True
T/F: Due to the relationship between the rate of enzyme catalysis and temperature, organisms living in boiling hot springs are also rapid growers with fast doubling times.
False
T/F: Taq polymerase was isolated from a thermophile and is used in the polymerase chain reaction (PCR) technique because it does not become inactivated at high temperatures.
True
Consider solution A (pH 6) and solution B (pH 9). Which of the following statements is CORRECT?
- Solution A is 300 times more acidic than solution B.
- Solution A is 3 times more acidic than solution B.
- Solution B is 3,000 times more alkaline (basic) than solution A.
- Solution B is 1,000 times more alkaline (basic) than solution A.
Solution B is 1,000 times more alkaline (basic) than solution A.
T/F: A bacterium’s pH optimum reflects the optimal pH of its intracellular environment.
False
Microbes can be grouped based on their tolerance to differing levels of salts in their environments. Knowing the meaning of these terms can help to predict which microbes might be found in a particular environment. Rank groupings from requiring low salt concentrations to high NaCl concentrations:
- nonhalophile
- halotolerant
- halophile
- extreme halophile (15-30%)
The ratio of the vapor pressure of the air in equilibrium with a substance to the vapor pressure of pure water is known as
water activity.
Organisms able to live in environments with high sugar concentrations are
osmophiles.
When water activity is low, an organism must
increase its internal solute concentration.
T/F: The sensitivity of DNA and RNA is one major reason water activity can limit microbial growth
False
A bacterium containing ________ provided with hydrogen peroxide will produce oxygen bubbles.
catalase
A halotolerant facultative anaerobic bacterium would grow BEST in a ________ environment.
oxygenated non-saline
Which of the following forms of oxygen is/are generally toxic to living organisms?
superoxide, hydrogen peroxide, and hydroxyl radicals are all toxic
Superoxide dismutase and catalase work together to convert superoxide into
oxygen.
T/F: A non-aerated or shaken liquid growth medium inoculated with a bacterium is one of the best ways to culture an obligate anaerobe.
False
What temperature is most commonly used for autoclaves to sterilize growth media and other devices prior to experimentation?
121°C
T/F: An unpressurized autoclave would not be able to sterilize a growth medium with contaminating bacteria but could still pasteurize it.
True
Many aromatic compounds used for growth substrates by bacteria are broken down during high heat autoclaving. Which is the BEST way to sterilize these aqueous solutions?
0.2 μm filter sterilization
A microbiologist wants to study the virus particles from a urine sample, but not any bacteria that might be present. How can the bacteria be eliminated without harming the viruses?
Filter the sample with a 0.2 ïm pore filter
In general, which group is MOST resistant to radiation?
viruses
Your laboratory supervisor has given you a plastic petri dish filled with soil to sterilize using radiation. What type of radiation will you use?
ionizing radiation
T/F: Sterility of a laminar flow hood is accomplished by filter-sterilized air passed through the hood quickly enough that non-sterile air does not flow into the work area.
True
The MOST effective antibiotics in preventing growth of disease-causing bacteria are
bacteriolytic or bacteriocidal.
A chemical that denatures proteins is MOST likely to be classified as a(n) ________ agent.
bacteriocidal
Which term is most relevant in describing the efficacy of an antimicrobial for use in a clinical setting?
minimum inhibitory concentration
Which method would be LEAST effective at sterilizing a glass hockey stick to use in the spread-plate method?
ultrahigh-temperature pasteurization
An antiseptic (or germicide) is distinguished from other sterilizing compounds by
being able to be used on living tissues without harm.
The major distinguishing difference between antiseptics and disinfectants is __________.
antiseptics can be used on living tissue
What does the minimum inhibitory concentration (MIC) of a chemical tell you?
It tells you the smallest concentration of the chemical that is needed to inhibit the growth of a specific microorganism.
Succinyl CoA as an intermediate:
Assume that the activity of the two novel enzymes found to covert α-ketoglutarate to succinate + CO2 do not result in formation of any succinyl-CoA as an intermediate. Which of the following would be expected as a result?
No GTP (ATP) formation by substrate-level phosphorylation occurs in the citric acid cycle of cyanobacteria.
How does a competitive inhibitor slow enzyme catalysis?
They compete with the substrate for the enzyme’s active site.
What enables competitive inhibitors to bind to a specific enzyme?
Competitive inhibitors have structures that resemble the enzyme’s substrate.
If high amounts of sulfanilamide are in the presence of an enzyme whose substrate is PABA, what outcome is expected?
The enzyme will stop functioning.
statements regarding competitive inhibitors is true?
Competitive inhibitors decrease the rate of enzyme activity.
Why do all enzymatic reactions need activation energy?
Energy is required to disrupt a substrate’s stable electron configuration.
What is meant by the statement “Enzymes are biological catalysts”?
Enzymes speed up the chemical reactions in living cells.
Why are enzymes important to biological systems?
Enzymes decrease the amount of activation energy required for chemical reactions to occur.
The role of an enzyme includes all EXCEPT which of the following?
- straining chemical bonds in a substrate so that they break easier
- lowering the activation energy of a reaction
- binding only one specific substrate to the enzyme active site
- reducing the rate of a reaction to allow for better control
reducing the rate of a reaction to allow for better control
Activation energy is the energy
required to transform all reactants into their reactive state
T/F: In a given chemical reaction, if the free energy of formation is known for all of the reactants and each of the products, the change in free energy can be calculated for the reaction.
True
During an oxidation reaction,
the donor molecule loses an electron and becomes oxidized.
T/F: If a substance is reduced, it gains electrons.
True
T/F: The energy released from the hydrolysis of coenzyme A is conserved in the synthesis of ATP.
True
What is meant by substrate-level phosphorylation?
Production of ATP by transferring phosphates directly from metabolic products to ADP
Aerobic respiration produces proton motive force (PMF). Understanding how this process takes place is critical to understanding the metabolic functions of cells. Correctly identify steps occurring in this typical electron transport chain diagram.
- electrons enter the chain from a primary electron donor
- protons are extruded as Fe/S protein is reduced by FMNH2
- Q-cycle rxns
- as the terminal electron acceptor is reduced, electrons exit the chain.
T/F: Depending on the particular metabolism of a bacterium, electron transport can be used to energize and rotate ATP synthase.
False
Microbial growth on the two-carbon acetate substrate invokes
both the citric acid and glyoxylate pathways.
T/F: Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.
True
Gluconeogenesis is the process of synthesizing __________.
glucose from other compounds
