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.
