Which of the following best describes the source of energy utilized to make PMF (proton motive force) for a photoorganoheterotroph. ? a. light ? b. oxidized metals ? c. carbon dioxide ? d. glucose
The Correct Answer and Explanation is:
The correct answer is a. light.
Explanation:
A photoorganoheterotroph is an organism that uses light as an energy source and organic compounds as a carbon source. This group of organisms is capable of photosynthesis or photophosphorylation, processes that convert light energy into chemical energy. The production of Proton Motive Force (PMF) in these organisms is primarily driven by light energy.
Here’s how it works:
- Absorption of Light: The photoorganoheterotroph absorbs light through specialized pigments (such as bacteriochlorophyll or chlorophyll) located in structures like the photosynthetic membrane or photosynthetic proteins.
- Photophosphorylation: When light is absorbed, it excites electrons in the pigment molecules. These high-energy electrons are then transferred through an electron transport chain (ETC) within the membrane. As electrons flow through the ETC, they are used to pump protons (H⁺) across the membrane from the inside to the outside. This creates a proton gradient.
- Proton Motive Force (PMF): The proton gradient, or PMF, stores energy across the membrane. The protons tend to move back through the membrane, but they can only do so through an enzyme complex called ATP synthase. As protons flow back through ATP synthase, the enzyme harnesses this movement to synthesize ATP, the main energy currency used by cells.
- Organic Carbon Source: While light is used for energy, the organism relies on organic compounds (such as glucose or other carbon sources) to build cellular structures and molecules necessary for growth. These organic compounds are typically obtained from the environment, not used directly to generate PMF.
Thus, light is the primary source of energy that drives the creation of PMF in photoorganoheterotrophs. The energy from light is converted to a proton gradient, which is then used to produce ATP, essential for the organism’s cellular activities.
