Exam 3 Study Guide Flashcards
Are electron donors oxidized or reduced?
Reduced
Are electron acceptors oxidized or reduced?
Oxidized (___ate, ex sulfate)
Can electron donors donate or receive electrons?
Donate
Can electron acceptors donate or receive electrons?
Receive
What are some examples of electron donors (organic and inorganic)?
NADH/NADPH as organic examples
H2S, H2, NH3 as inorganic examples
What are some examples of electron acceptors?
Sulfate - nitrate
O2 - pyruvate
What happens when an electron donor donates their elctron?
Becomes oxidized (loses electron)
What happens when an electron acceptor receives their electron?
Becomes reduced (received electron)
Where are the electron donors located in an ETS (electron transport system)?
Start of electron transport chain
Where are the electron acceptors located in an ETS (electron transport system)?
End of electron transport chain
What is the carbon source of a fermenting cell?
Glucose (6C)
What is the energy source of a fermenting cell?
Chemical
What is the electron source of a fermenting cell?
NADH
What is the path+products of fermentation in a cell?
Glucose (6C) –EMP and/or ED–> 2 pyruvate (6C)
OR
NADH/NADPH + ATP –electron–> 2 pyruvate (6C)
2 pyruvate —-> fermentation products
What are the organisms that can ferment/oxidize substances in their cells?
Chemotroph
Organotroph
Heterotroph
What is the carbon source in a respiring cell?
Glucose (6C)
What is the electron source in a respiring cell?
NADH
What is the energy source in a respiring cell?
Chemical
What is the path+products of a respiring cell?
Glucose (6C) –EMP/ED OR NADH/NAPH+ATP –> 2 pyruvate
2 pyruvate (2*3C) –> PDC (acetyl coA + CO2 + NADH)
PDC –> TCA (CO2 –> NADH + ATP)
TCA –> ETS (recycle NADH/NADH to oxidized form)
Which step of respiration produces a lot of NADH?
TCA
Which step of respiration recycle NADH?
ETS
3 components of ETS (electron transport chain)
1) initial substrate oxidoreductase (remove electron from donor)
2) mobile electron carrier (carry electron)
3) terminal oxidase (accepts electron)
Why must the ETS be embedded in the cell membrane?
To keep ion gradient separated (H+ and PMF)
What happens during ETS operation?
1) recycles donor (NADH–>NAD)
2) proton motive force (across membrane)
3) reduce electron acceptor
PMF (proton motive force) uses…
1) ATP production / ATP synthase / oxidative
2) coupled active transport
3) antiport
4) rotate flagella
Is fermentation or respiration more efficient?
Respiration
Does fermentation or respiration produce CO2?
Respiration
Fermentation creates fermentation products
What fermentation step is ATP produced?
SLP
What respiration step is ATP produced?
SLP and oxidative
Does fermentation or respiration produce more ATP?
Respiration
What is the electron donor for fermentation?
NADH
What is the electron donor for respiration?
NADH
What is the electron acceptor in fermentation?
Pyruvate
What is the electron acceptor in respiration?
O2
Nitrates
Sulfates
Does fermentation or respiration contain the ETS and PMF?
Respiration
Fermentation may occur in a respiring cell when…
the respiring cell uses all of the electron accepetor
Lithotrophs are also…
Autotrophs
Litotrophs and phototrophs use ____ as their carbon source
CO2
What uses H2O as the e-donor in phosphorylation?
Green plants
Cyanobacteria
Organisms that use oxygenic photosynthesis
By-product is O2
Oxygenic photosynthesis occurs in…
Green plants
Cyanobacteria
What uses H2S as the electron donor in phosphorylation?
PS1
ANoxygenic PS
What uses chlorophyll as the electron donor in phosphorylation?
PS2
What are the 3 requirements for biosynthesis anabolism to occur?
Essential elements
ATP
Reducing power (electron carrier)
What are the essential elements needed for biosynthesis? Where do you get them?
C (CO2 and organic)
N (form that is easily accessible like NH3)
CO2 fixation definition:
CO2 –> organic form
CO2 fixation enzyme:
Rubisco (calvin cycle)
CO2 fixation is done by who? Is it widespread?
Green plants (algae) and cyanobacteria
No
What are the specialized cell structures in cyanobacteria for CO2 fixation?
Carboxysomes
What is the input of energy for CO2 fixation? Input of reducing power?
A lot
A lot
What is the input of energy for N2 fixation? Input of reducing power?
A lot
A lot
N2 fixation definition:
N2 (triple bond) –> NH3
N2 fixation enzyme
Nitrogenase (O2 sensitive)
Who uses N2 fixation? Is it widespread?
Soil bacteria
Rhizobium (luminous plant roots)
Cyanobacteria
No
What are the specialized cells or structures in cyanobacteria in regard to N2 fixation?
Heterocysts
What is FA biosynthesis? What are the parts of it?
Enzyme fatty acid synthase
Repeating unit acetyl-coA
Even numbered 2C building block
What is purine/pyrimide biosynthesis? What are the parts of it?
Precursor PRPP
Nucleotides for RNA made first
What is amino acid biosynthesis? What are the parts of it?
Transfer of amino groups between substrates
Transamination
What is made from 1 glucose through EMP?
two pyruvate
What is made from 1 glucose through ED?
1 ATP, 1 NADH, 1 NADPH, and 2 pyruvate
What is made from fermentating cells?
homolactic - 2 lactic acid
ethanolic - 2 ethanol and 2 CO2
heterolactic - 1 lactic acid, 1 ethanol, 1 CO2
mixed acid - acetate, formate, lactate, succinate, ethanol, H2, CO2
What is made from respiring cells?
38 ATP
Cyanobacteria and green plants carry out the same…
Oxygenic PS
CO2 fixation (Calvin cycle and rubisco used
N2 fixation
In the ETS components, what are enzymes?
Initial substrate oxioreductase
Terminal oxidase
In the ETS components, what kicks protons out?
Initial substrate oxidoreductase
Terminal oxidase
In the ETS components, which ones are mobile?
Mobile electron carrier
Which of the following is FALSE regarding chemolithotrophic microorganisms?
A. Electron donors for respiration include Fe2+, H2S, and NH+4.
B. They use inorganic compounds as electron donors.
C. They include methanogens.
D. Light absorption provides them with electrons.
D. Light absorption provides them with electrons.
Which of the following is NOT a pathway to convert glucose into pyruvate?
A. Glycolysis
B. Pentose-phosphate pathway
C. Tricarboxylic acid cycle
D. Entner-Doudoroff pathway
C. Tricarboxylic acid cycle
Fermentation pathways have the __________ in common.
A. oxidation of NADH to NAD+
B. production of ethanol
C. use of oxygen as an electron acceptor
D. production of lactic acid
A. oxidation of NADH to NAD+
After completion of a turn of the tricarboxylic acid (TCA) cycle, most of the energy originally present in glucose is now found in
A. pyruvate.
B. NADH.
C. ATP.
D. carbon dioxide.
B. NADH.
The proton motive force is a source of energy that can directly power all of the following EXCEPT the
A. production of ATP.
B. synthesis of proteins from amino acids.
C. import of other ions against their concentration gradients.
D. rotation of bacterial flagella.
B. synthesis of proteins from amino acids.
The electrical potential across the membranes in most cells is such that
A. the inside of the cell is negative relative to the outside of the cell.
B. the inside of the cell is positive relative to the outside of the cell.
C. there is no charge separation across the membrane, and hence no voltage difference.
D. the inside of the cell is negative so all positive particles are expelled.
A. the inside of the cell is negative relative to the outside of the cell.
A certain bacterial species contains carboxysomes. From this information, it can be inferred that the species is capable of
A. the reductive TCA cycle.
B. carbon fixation.
C. nitrogen fixation.
D. polyketide synthesis.
B. carbon fixation.
Protein-bounded cells containing Rubisco are called…
carboxysomes
The Calvin cycle incorporates which inorganic compound into an organic molecule?
A. Potassium phosphate
B. Sodium nitrate
C. Calcium sulfate
D. Carbon dioxide
D. Carbon dioxide
Which of the following is NOT a mechanism to prevent oxygen from entering the environment of nitrogenase?
A. Reduction of iron to prevent oxidation
B. Using specialized cells to sequester nitrogenase
C. Separating oxygenic photosynthesis and nitrogen fixation temporally
D. Protective proteins sequestering the nitrogenase
A. Reduction of iron to prevent oxidation
Nitrogen fixation is ecologically important because
A. proteins and nucleic acids require nitrogen as part of their structure.
B. it releases oxygen.
C. diatomic nitrogen is toxic.
D. nitrogen is directly necessary for carbohydrate catabolism.
A. proteins and nucleic acids require nitrogen as part of their structure.
Terrestrial plants cannot directly use atmospheric N2 because
A. plants lack the enzyme nitrogenase.
B. atmospheric nitrogen concentrations are very low.
C. oxygenic photosynthesis and nitrogen fixation are incompatible.
D. only marine organisms can fix nitrogen.
A. plants lack the enzyme nitrogenase.
Nitrogenase
A. works well in any environment.
B. requires oxygen as an electron acceptor.
C. requires many ATP and electrons to reduce N2 to 2NH4+.
D. is a relatively small enzyme.
C. requires many ATP and electrons to reduce N2 to 2NH4+.
Nitrogen fixation genes are activated by
A. nitrogen fixation genes that are constitutively active.
B. high levels of oxygen gas.
C. high levels of ammonia.
D. low levels of ammonia.
D. low levels of ammonia.
Amino acid synthesis differs from fatty acid synthesis in that
A. only fatty acid synthesis requires reducing agents.
B. amino acid synthesis occurs only in autotrophs, whereas fatty acid synthesis occurs in both autotrophs and heterotrophs.
C. only amino acid synthesis is an anabolic process.
D. only fatty acid synthesis occurs via a cyclic process.
D. only fatty acid synthesis occurs via a cyclic process.
Which of the following chemical pairs provides a metabolic strategy that is an example of both lithotrophy and anaerobic respiration?
A. electron donor NH3; electron acceptor O2
B. electron donor Fe2+; electron acceptor O2
C. electron donor glucose; electron acceptor O2
D. electron donor H2; electron acceptor SO42–
E. electron donor glucose; electron acceptor Fe3+
D. electron donor H2; electron acceptor SO42–
An organism that gets its energy from light is known as a _______. These organisms also usually grow as autotrophs, meaning that they require carbon in the form of _____.
phototroph
CO2
Animals and most microorganisms are classified as chemoorganoheterotrophs. The prefixes “chemo,” “organo,” and “hetero” refer to how the organism meets its needs, respectively, for:
A. electrons, energy, and carbon
B. carbon, energy, and electrons
C. electrons, carbon, and energy
D. carbon, electrons, and energy
E. energy, electrons, and carbon
E. energy, electrons, and carbon
The most widely utilized energy carrier in the cell is ATP. It is composed of which of the following? (Select all that apply.)
A. a 5-carbon sugar
B. titanium
C. 3 phosphate groups
D. a fatty acid
E. a nitrogenous base
F. alanine
A. a 5-carbon sugar
C. 3 phosphate groups
E. a nitrogenous base
Fermentation and respiration represent two major forms of _____ in chemoorganoheterotrophs.
catabolism
Ethanolic fermentation results in which of the following end product(s)?
A. alcohol
B. acetone
C. lactic acid
D. oxygen
E. carbon dioxide
F. water
A. alcohol
E. carbon dioxide
Lactic acid fermentation is so named because lactic acid is which of the following?
A. source of energy
B. intermediate electron carrier
C. key intermediate
D. starting substrate
E. end product
E. end product
Of the following, which phenotype would most likely be observed in mutants of E. coli lacking a key enzyme in the ED pathway?
A. lack of flagellar motility
B. loss of ability to grow anaerobically
C. increased virulence
D. inability to form biofilms
E. reduced ability to colonize the mammalian gut
E. reduced ability to colonize the mammalian gut
Which of the following pathways would be preferentially used by a cell running low on energy?
Choose one:
A. nitrogen fixation
B. glycolysis
C. Calvin cycle
D. pentose phosphate pathway
E. gluconeogenesis
B. glycolysis
Identify the three main catabolic routes in bacteria by which glucose is converted to pyruvate.
A. Krebs cycle
B. electron transport chain
C. pentose phosphate pathway
D. Calvin cycle
E. Embden-Meyerhof-Parnas pathway
F. Entner-Doudoroff pathway
C. pentose phosphate pathway
E. Embden-Meyerhof-Parnas pathway
F. Entner-Doudoroff pathway
If one molecule of glucose were fully catabolized via aerobic respiration to CO2 and H2O, the ATP yield would be roughly _____ that obtained from fermentation.
20 times
Ultimately, respiration and fermentation are simply different ways to conclude sugar catabolism. Following the energy-yielding reactions, respiring cells pass electrons to oxygen (or other external inorganic oxidant), while fermenting cells dump electrons back onto a partially oxidized organic molecule (such as pyruvate), which then exits the cell as a waste product. Either way, the goal is to do which of the following?
A. generate as much NADH as possible (then synthesize more NAD+ if necessary)
B. fully oxidize NADH into CO2 and H2O
C. break down NADH into biosynthetic precursors
D. stimulate de novo production of NAD+
E. recycle NADH back to NAD+
E. recycle NADH back to NAD+
The pyruvate dehydrogenase complex plays an important role in cellular metabolism by connecting ______ to _______.
glycolysis
the TCA cycle
If a small molecule is found at greater concentration inside the cell than outside, it can be concluded that
A. the molecule can freely move across the cell membrane.
B. this represents the maximal entropy state for that molecule.
C. energy was required to produce the concentration gradient.
D. the concentration gradient cannot be used to do work.
C. energy was required to produce the concentration gradient.
An example of catabolism is
A. lipid synthesis from fatty acids and glycerol.
B. starch production from glucose.
C. amino acid polymerization into proteins.
D. glucose oxidation to pyruvate.
D. glucose oxidation to pyruvate.
All of the following types of metabolism use a membrane-associated electron transport system (ETS) EXCEPT for
A. fermentation.
B. mitochondrial respiration.
C. lithotrophy.
D. organotrophy.
E. phototrophy.
A. fermentation
Electron transport chains pump which of the following across membranes?
A. Ions
B. Neutrons
C. Molecules
D. Atoms
A. Ions
Which of the following processes contribute to the proton motive force during aerobic respiration?
A. ATP synthesis
B. glycolysis
C. TCA cycle
D. electron transport system
E. fermentation
F. carbon fixation
B. glycolysis
C. TCA cycle
D. electron transport system
Which of the following best describes how the electron transport system (ETS) functions?
A. Electron transport releases energy, which is used to pump protons across the cell membrane.
B. Electrons remain as part of intact hydrogen atoms that become separated at the terminal oxidant to release energy.
C. Periplasmic NADH is oxidized to release protons and electrons, which enter the cytoplasm.
D. NADH is pumped to the exterior side of the membrane, where it is reoxidized to release protons and electrons.
E. Protons entering the cell through membrane channels are coupled to the antiport of electrons.
A. Electron transport releases energy, which is used to pump protons across the cell membrane.
What is the order of events for energy from cellular metabolism converted to ATP by respiring organisms?
Glycolysis and TCA cycle generate NADH and FADH
NADH and FADH oxidized by electron transport proteins
Electron transport releases energy that is used to translocate H+
An electrochemical gradient of protons is established (delta p)
Influx of H+ through ATP synthase drives ATP production
What is the order of electron acceptors in glycolysis and TCA in order to establish a transmembrane proton gradient?
NAD+
Oxidoreductase
Quinone
Terminal oxidase
Oxygen
Which of the following is not an example of anabolism?
A. energy production
B. protein production
C. polysaccharide production
D. lipid production
A. energy production
The requirements of biosynthesis are carbon and other essential elements, as well as which of the following?
A. oxidizing agents and energy for anabolic enzymes
B. reducing agents and energy for catabolic enzymes
C. reducing agents and energy for anabolic enzymes
D. oxidizing agents and energy for catabolic enzymes
C. reducing agents and energy for anabolic enzymes
In the Calvin cycle, carbon dioxide is covalently incorporated into glucose. This is known as which of the following?
A. CO2 catabolism
B. CO2 oxidation
C. CO2 heterotrophy
D. CO2 fixation
D. CO2 fixation
Carboxysomes are structures found in cyanobacteria and chloroplasts. They consist of a protein shell that contains the enzyme Rubisco. The purpose of the carboxysome is to trap
A. CO2 so that it reaches concentrations necessary to drive Rubisco.
B. glucose so that it does not damage other parts of the cell.
C. PGA so that it is converted to G3P more rapidly.
D. Rubisco so that it does not catalyze carboxylation.
A. CO2 so that it reaches concentrations necessary to drive Rubisco.
Which of the following is not a method of carbon fixation?
A. reductive acetyl-CoA pathway
B. reverse TCA cycle
C. 3-hydroxypropionate cycle
D. TCA cycle
E. Calvin cycle
D. TCA cycle
Which of the following statements is true?
A. All living organisms depend on nitrogen-fixing prokaryotes.
B. All living organisms can fix nitrogen.
C. Organisms that fix nitrogen cannot fix CO2.
D. Not all ecosystems require fixed nitrogen.
A. All living organisms depend on nitrogen-fixing prokaryotes.
Which of the following organisms are unable to fix nitrogen?
A. yeasts, such as Candida albicans
B. soil and wetland bacteria, such as Azotobacter
C. endosymbionts of leguminous plants, such as Rhizobium
D. most phototrophic bacteria, such as cyanobacteria
A. yeasts, such as Candida albicans
Nitrogen fixation is under tight regulation and only occurs under certain conditions when it is needed. Why is this process so tightly regulated?
A. For carbon fixation to occur in a cell, nitrogen fixation must be turned off.
B. Only a few, specific molecules in the cell contain nitrogen, and so fixed nitrogen is not frequently needed.
C. The amount of N2 in the atmosphere is limited.
D. Nitrogen fixation costs substantial energy.
D. Nitrogen fixation costs substantial energy.
In which situation is nitrogenase expression up-regulated?
A. low NH4+ and low O2 conditions
B. high NH4+ and high O2 conditions
C. high NH4+ and low O2 conditions
D. low NH4+ and high O2 conditions
A. low NH4+ and low O2 conditions
Filamentous cyanobacteria form specialized cells that have lost the ability to perform photosynthesis and so do not produce oxygen. These cells, called __________, maintain anoxic conditions for nitrogenase.
A. leghemoglobins
B. heterocysts
C. carboxysomes
D. polyketides
B. heterocysts
Which of the following is not a carbon fixation pathway?
A. 3-hydroxypropionate pathway
B. Reverse TCA
C. Fatty acid synthesis
D. Reductive acetyl Co-A pathway
C. Fatty acid synthesis
What are some features of ATP? NADH? Both?
ATP
Can transfer phosphate groups
Activates sugars for glycolysis
Hydrolysis can be coupled to drive biosynthetic reactions.
Energy stored in bonds between two terminal phosphates
NADH
Contains nicotinamide ring
Can donate hydrogen atoms
Supplies the electron transport chain
Both
Contains adenosine
Diffusible through the cytoplasm
Two (net) molecules are generated via glycolysis.
What are some characteristics of respiration? Fermentation? Both?
Respiration
High ATP yield; most from oxidative phosphorylation
Most carbon released as CO2
Electrons reduce an external electron acceptor (e.g., O2).
Fermentation
Low ATP yield; primarily from glycolysis
Electrons from catabolism end up back on partially oxidized substrate.
Most carbon remains in organic form.
Both
Important for catabolism of sugars
NADH major electron carrier
Pyruvate is major intermediate.
How to tell whether a reaction is an oxidation or reduction?
Oxidation will have a free electron on the product side
Reduction will have a free electron on the reactant side
