topic 4-Microorganisms and Their Metabolism

Which of the following describes organisms that use inorganic compounds as their energy source?

• Phototrophs

• Chemolithotrophs

• Chemoorganotrophs

• Heterotrophs

Answer explanation

Chemolithotrophs are organisms that obtain energy by oxidizing inorganic compounds, distinguishing them from phototrophs (light energy), chemoorganotrophs (organic compounds), and heterotrophs (organic carbon).

Organisms that use light as their energy source are called:

• Autotrophs

• Heterotrophs

• Phototrophs

• Chemotrophs

Answer explanation

Organisms that use light as their energy source are called phototrophs. They convert light energy into chemical energy, distinguishing them from autotrophs, heterotrophs, and chemotrophs, which use different energy sources.

Which group of microorganisms uses CO2 as their sole carbon source?

• Heterotrophs

• Autotrophs

• Chemoorganotrophs

• Mixotrophs

Answer explanation

Autotrophs are microorganisms that use carbon dioxide (CO2) as their sole carbon source, converting it into organic compounds through processes like photosynthesis or chemosynthesis. Heterotrophs and others rely on organic sources.

What type of metabolism is unique to Cyanobacteria among prokaryotes?

• Anoxygenic photosynthesis

• Oxygenic photosynthesis

• Chemolithotrophy

• Fermentation

Answer explanation

Cyanobacteria are unique among prokaryotes for performing oxygenic photosynthesis, a process that uses sunlight to convert water and carbon dioxide into glucose and oxygen, distinguishing them from those that perform anoxygenic photosynthesis.

Which of the following is NOT a characteristic of extremophiles?

• They thrive in extreme environments

• They are all prokaryotes

• They have specialized adaptations

• They include both bacteria and archaea

Answer explanation

The statement "They are all prokaryotes" is incorrect because extremophiles include both prokaryotes (bacteria and archaea) and eukaryotes. Therefore, not all extremophiles are prokaryotic.

Chemoorganotrophs obtain their energy from:

• Inorganic compounds

• Light

• Organic compounds

• CO2

Answer explanation

Chemoorganotrophs obtain their energy from organic compounds, which they metabolize to generate energy. This distinguishes them from other groups that utilize inorganic compounds, light, or CO2.

Which type of microorganism uses inorganic compounds for energy and CO2 for carbon?

• Photoautotroph

• Chemoheterotroph

• Chemoautotroph

• Photoheterotroph

Answer explanation

Chemoautotrophs use inorganic compounds for energy and fix CO2 for carbon. This distinguishes them from photoautotrophs, which use light, and chemoheterotrophs, which rely on organic compounds.

Anoxygenic photosynthesis is characterized by:

• Production of oxygen

• Use of H2O as an electron donor

• Use of compounds other than H2O as electron donors

• Occurrence in plants

Answer explanation

Anoxygenic photosynthesis does not produce oxygen and uses electron donors other than water, such as hydrogen sulfide or organic compounds. This distinguishes it from oxygenic photosynthesis, which relies on water.

Which of the following is TRUE about heterotrophs?

• They use CO2 as their carbon source

• They require organic compounds for carbon

• They all perform photosynthesis

• They are all prokaryotes

Answer explanation

Heterotrophs require organic compounds for carbon, as they cannot utilize CO2 like autotrophs. They do not all perform photosynthesis and can be found among both prokaryotes and eukaryotes.

What is the primary energy source for chemolithotrophs?

• Organic compounds

• Light

• Inorganic compounds

• Heat

Answer explanation

Chemolithotrophs primarily derive energy from inorganic compounds, such as hydrogen sulfide or ammonia, rather than organic compounds or light. This distinguishes them from other organisms that rely on organic sources or photosynthesis.