Q.89 The organisms that obtain energy from inorganic compounds are known as
(A) Autotrophs
(B) Organotrophs
(C) Lithotrophs
(D) Phototrophs
Correct Answer: (C) Lithotrophs
Lithotrophs are organisms that derive energy specifically from the oxidation of inorganic compounds, such as hydrogen sulfide, ammonia, or ferrous iron. This process, known as chemolithotrophy, powers their metabolism in environments lacking sunlight, like deep-sea vents.
Option Explanations
Autotrophs broadly synthesize organic compounds from inorganic carbon sources like CO₂, using either light or chemical energy; examples include plants and chemoautotrophs, but the term does not specify energy from inorganic compounds.
Organotrophs obtain energy by oxidizing organic compounds, such as glucose or amino acids; they contrast with lithotrophs by relying on carbon-based electron donors.
Lithotrophs use reduced inorganic substances (e.g., H₂S, NH₃, Fe²⁺) as electron donors for energy via oxidation; many are bacteria like Nitrosomonas or Thiobacillus, fitting the question precisely.
Phototrophs harness light energy for metabolism, including photoautotrophs like cyanobacteria; they do not use inorganic chemical oxidation.
SEO-Friendly Article
Organisms that obtain energy from inorganic compounds play a vital role in extreme ecosystems, powering life without sunlight. Known as lithotrophs, these microbes oxidize substances like hydrogen sulfide or ammonia to generate ATP, essential for CSIR NET Life Sciences aspirants studying microbial nutrition.
Types of Energy Acquisition
- Lithotrophs (Chemolithotrophs): Use inorganic electron donors (e.g., Fe²⁺ → Fe³⁺); found in hydrothermal vents.
- Organotrophs: Rely on organic donors like sugars; common in soil bacteria.
- Phototrophs: Capture photons; e.g., purple sulfur bacteria.
This classification stems from electron donor sources, distinguishing lithotrophs clearly.
Examples and Applications
Lithotrophs like sulfur-oxidizing Thiobacillus thrive in acidic mines, aiding bioremediation. In biotechnology, they inspire sustainable energy models mimicking chemosynthesis. For competitive exams, note: lithotrophs are often autotrophic but defined by inorganic energy sourcing.
