Question

Which of the chlorophyll type ejects the electron during photophosphorylation? (a) Chlorophyll 'b' (b) Chlorophyll 'a' (c) Chlorophyll 'a' and 'b' (d) Xanthophyll

Short answer

Therefore, Chlorophyll 'a' (option -b) is the type that ejects the electron during photophosphorylation.

Step-by-step solution

Understanding Photophosphorylation

Photophosphorylation is the process where light energy is used to convert ADP to ATP, which later provides the chemical energy for other reactions. It is a part of light-dependent reactions of photosynthesis, and it's where the chlorophyll molecules come in play.

Determine role of Chlorophyll 'a' and Chlorophyll 'b'

Chlorophyll 'a' and 'b' are responsible for the absorption of light energy. Specifically, Chlorophyll 'a' is the only pigment that can directly convert light energy into chemical energy by ejecting an electron that moves down the electron transport chain.

Eliminate the other options

Chlorophyll 'b', on the other hand, aids in capturing and passing the light energy to chlorophyll 'a'. It cannot eject an electron during photophosphorylation. Xanthophylls are accessory pigments and are not directly involved in photophosphorylation. They cannot eject an electron.

Key concepts

Photophosphorylation

Photophosphorylation is a vital process occurring within the chloroplasts of plant cells. It involves the conversion of light energy, harnessed from sunlight, into chemical energy in the form of ATP. This conversion is possible because of the precise mechanisms by which chlorophyll molecules interact with light.

In this intricate reaction, chlorophyll 'a' plays a central role. When chlorophyll 'a' absorbs light, it becomes energized and has excess energy in its electrons. This causes the ejection of an electron, which is then transferred down an electron transport chain. This movement of the electron establishes a proton gradient across the thylakoid membrane.

As protons flow back through ATP synthase, from high to low concentration, the enzyme uses this energy to synthesize ATP from ADP and inorganic phosphate. This conversion of ADP to ATP during the light-dependent reaction occurs because of photophosphorylation, providing crucial energy for further stages of photosynthesis.

Light-dependent reactions

Light-dependent reactions are the initial phase of photosynthesis. These reactions take place in the thylakoid membranes of the chloroplasts. Their primary aim is to capture and utilize the energy from sunlight to produce ATP and NADPH, energy carriers essential for the subsequent steps of photosynthesis.

During these reactions, sunlight strikes the chlorophyll molecules, primarily chlorophyll 'a', causing them to become excited and release electrons. These electrons travel through a series of proteins in the electron transport chain, while their energy is used to create an Electrochemical gradient, which fosters the production of ATP via the process of photophosphorylation.

The electrons continue their journey, being transferred to NADP+ to form NADPH. This transformation is critical as both ATP and NADPH serve as the energy currency and reducing power needed to drive the Calvin cycle, demonstrating the indispensable nature of light-dependent reactions in the photosynthetic process.

Photosynthesis

Photosynthesis is the cornerstone of plant energy metabolism, enabling the conversion of light energy into chemical energy stored as glucose. This complex process primarily occurs in two stages: light-dependent reactions and the Calvin cycle.

The light-dependent reactions generate ATP and NADPH, as earlier explained, which are then utilized in the light-independent reactions, often termed the Calvin cycle. During this cycle, these energy carriers facilitate the conversion of carbon dioxide and water into glucose, the primary source of energy and carbon for the plant.

Photosynthesis is not just vital for plants but for all life on earth. It forms the base of the food chain, providing energy for almost every organism. Additionally, it plays a critical role in maintaining atmospheric oxygen levels, as oxygen is a byproduct of the light-dependent reactions where water molecules are split.