What do some photosynthetic bacteria use as a source of electrons instead of water? a. oxygen (O2) b. hydrogen sulfide (H2S) c. organic compounds (e.g., CH3COO−) d. nitrate (NO3-)

Verified step by step guidance

1. Identify the process involved: The question pertains to photosynthesis in bacteria, specifically the source of electrons used in the light-dependent reactions.
2. Recall the general photosynthesis equation: In plants, water (H2O) is typically used as the electron donor, splitting into oxygen (O2), electrons, and protons under the influence of sunlight.
3. Consider alternative electron sources: Some bacteria use different electron donors than water. These can include substances like hydrogen sulfide (H2S) or organic compounds.
4. Eliminate incorrect options: Oxygen (O2) is a product of photosynthesis, not an electron donor. Nitrate (NO3-) and organic compounds are less commonly used as primary electron sources in photosynthetic processes compared to hydrogen sulfide (H2S) in some bacteria.
5. Select the correct answer: Based on the information and elimination of other options, hydrogen sulfide (H2S) is used as a source of electrons by some photosynthetic bacteria, making option 'b' the correct answer.

Key Concepts

Photosynthesis

Photosynthesis is the process by which organisms, primarily plants and some bacteria, convert light energy into chemical energy stored in glucose. In this process, water is typically used as an electron donor, but some photosynthetic bacteria can utilize alternative sources, which allows them to thrive in diverse environments.

Electron Donors in Photosynthesis

Electron donors are substances that provide electrons during the photosynthetic process. While water is the most common electron donor in plants, certain photosynthetic bacteria can use other compounds such as hydrogen sulfide (H2S) or organic compounds, which can influence their metabolic pathways and ecological niches.

Types of Photosynthetic Bacteria

Photosynthetic bacteria are categorized into groups based on their electron donors and photosynthetic mechanisms. For example, purple and green sulfur bacteria utilize hydrogen sulfide, while some other bacteria can use organic compounds. Understanding these classifications helps in recognizing the diversity of metabolic strategies in microbial ecosystems.