Photosynthesis, primarily conducted by plants, relies on an incredibly effective mechanism for converting energy. To create chemical energy, it is essential to first capture and move sunlight. This process occurs with minimal loss and at remarkable speed. A recent study highlights the significant role that quantum mechanical effects play in this conversion.
The effective transformation of solar energy into forms of chemical energy that can be stored is a goal many engineers aspire to achieve. Nature discovered an ideal approach to this challenge billions of years ago. This new research reveals that quantum mechanics, often thought to belong solely to the realm of physics, is also crucial in the field of biology.
Organisms that perform photosynthesis, such as green plants, utilize quantum mechanical phenomena to capture sunlight, as explained by Professor Jürgen Hauer: “When a leaf absorbs light, the energy that excites the electrons gets spread over multiple states of each excited chlorophyll molecule; we refer to this as a superposition of excited states. This is the initial phase of almost loss-free energy transmission occurring within and between molecules, facilitating the efficient transfer of solar energy. Hence, quantum mechanics is fundamental in comprehending the early stages of energy transfer and charge separation.”
This process, which cannot be thoroughly explained by classical physics alone, is continuously at work in green plants and various photosynthetic organisms, like photosynthetic bacteria. However, the intricate details of these mechanisms are still not fully understood. Hauer and lead author Erika Keil view their research as a significant step toward uncovering how chlorophyll, the green pigment in leaves, functions. The application of these insights into designing artificial photosynthesis systems could enhance the use of solar energy for generating electricity or for photochemical processes with unprecedented efficiency.
For their research, the scientists investigated two specific segments of the light spectrum where chlorophyll captures energy: the lower energy Q region (ranging from yellow to red) and the higher energy B region (spanning blue to green). The Q region comprises two distinct electronic states that are quantum mechanically linked. This linkage enables seamless energy transfer within the molecule. Subsequently, the system relaxes by ‘cooling,’ which involves dissipating energy as heat. Their findings illustrate that quantum mechanical effects can significantly impact processes relevant to biology.
