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Grad Soil Midterm
Terms in this set (13)
Heterotroph vs. Autotroph
Autotrophs are organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis). Heterotrophs cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition.
Organotroph vs. Lithotroph
Organotrophs: Organic compounds are used as electron donor. Lithotrophs: Inorganic compounds are used as electron donor.
Phototroph vs. Chemotroph
Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which utilize solar energy.
Most fungi are (choose the right prefix) (hetero/auto)trophs, (organo/litho/aqua)trophs, and (photo/chemo)trophs
You discovered an organism that uses NO3- as an electron acceptor instead of oxygen. What does this tell us about whether this is an organotroph or a lithotroph? Explain your reasoning.
Lithotroph - because to an organotroph always uses an organic compound -defined as a compound with C and H- as an electron acceptor
Match the following to their function:
(A) Electron transport chain
(B) Calvin cycle
(C) Krebs/TCA/Citric acid cycle
(1) Fixes CÓ and is found in autotrophs
(2) Generates electron carriers and ATP via substrate-level phosphorylation
(3) Produces a proton gradient across the cell membrane that drives ATP synthase
A -> 3
B -> 1
C -> 2
Why would the electron transport chain run "in reverse"? What is produced? Give an example of a classification of organisms that would use this process.
Chemolithotrophs using an electron donor with a higher redox potential than NAD(P)+/NAD(P)H, such as nitrite or sulfur compounds, must use energy to reduce NAD(P)+. This energy is supplied by consuming proton motive force to drive electrons in a reverse direction through an electron transport chain and is thus the reverse process as forward electron transport. In some cases, the energy consumed in reverse electron transport is five times greater than energy gained from the forward process. Autotrophs can use this process to supply reducing power for inorganic carbon fixation.
7. Calculate the oxidation state of S in the following compounds:
(B) S0 (elemental S)
D) -1 and oxygen is +0.5
Chromatium (purple S bacteria) can transform H2S to S0. Is this reduction or oxidation? Is H2S serving as the electron donor or the electron acceptor?
Look at the provided table. If an organism needs to transform CH2O to CÓ, which of the following is the most favourable half reaction to pair it with (under standard conditions)?
(A) Ó + 4H+ + 4e- -> 2H2O
(B) NǑ- + 10H+ + 6e- -> NH4+ + 2H2O
(C) Fě+ + e- -> Fé+
A -> because it has the biggest Eh difference
Are most enzymes
(D) nucleic acids
Describe the difference between hydrolases and oxidases. Give one example of each.
hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond
A-B + H2O → A-OH + B-H
ex) esterase, nucleases
oxidase is an enzyme that catalyzes an oxidation-reduction reaction, especially one involving dioxygen (Ó) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydrogen peroxide (H2Ó).
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