Biology, MCAT QBook question 248

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Biology, MCAT QBook question 248

Post by kleshchuk » Wed May 13, 2020 8:07 pm

It says that both Streptomyces and Pseudomonas show growth in the presence and absence of sunlight, which makes them chemotrophic. The definition for chemosynthesis is the synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, usually in the absence of sunlight. Based on that, the reason that they are both chemotrophic is more on the fact that they derive energy from carbon source in the absence of light. The fact that there is growth in the presence of sunlight is not really the concern here. The concern is that they grow in the absence of sunlight.
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Re: Biology, MCAT QBook question 248

Post by NS_Tutor_Mathias » Fri May 15, 2020 2:27 pm

Right, the presence of sunlight isn't really what interests you: You're just taking note that they don't seem to depend entirely on sunlight to generate energy, meaning both forms of phototrophy are out. The final part of the explanation is a little off - growing in the presence of oxygen has little to do with autotrophy. However, the ability to grow on minimal media does seem to suggest that pseudomonas is an autotroph to a degree - making C the most reasonable answer.
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