All of the events listed below occur in the energy-capturing light-dependent reactions of photosynthesis EXCEPT
Oxygen is produced
NADP+ is reduced to NADPH
Carbon dioxide is incorporated into 3-Phosphoglycerate
ADP is phosphorylated to yield ATP
Light is absorbed and funneled to a reaction center chlorophyll a
To determine which of the events listed does not occur in the light-dependent reactions of photosynthesis, we need to understand what happens in these reactions.
The light-dependent reactions of photosynthesis occur in the thylakoid membranes of chloroplasts. Their main function is to capture and convert light energy into chemical energy in the form of ATP and NADPH.
Let's go through each event and see if it happens in the light-dependent reactions:
1. Oxygen is produced: Yes, oxygen is indeed produced as a byproduct of the light-dependent reactions. During the process, water molecules are split, and oxygen gas is released.
2. NADP+ is reduced to NADPH: Yes, this is a crucial step in the light-dependent reactions. NADP+ molecules accept high-energy electrons (released from the splitting of water) and hydrogen ions (H+) to form NADPH, which carries the captured energy to the next stage of photosynthesis.
3. Carbon dioxide is incorporated into 3-Phosphoglycerate: This event actually occurs in the Calvin cycle, which is the second stage of photosynthesis. In the light-independent reactions (Calvin cycle), carbon dioxide is fixed and incorporated into organic molecules.
4. ADP is phosphorylated to yield ATP: Yes, this is one of the main purposes of the light-dependent reactions. The captured light energy is used to generate ATP from ADP (adenosine diphosphate) through a process called phosphorylation. This ATP is then utilized in the light-independent reactions to fuel the conversion of carbon dioxide into glucose.
5. Light is absorbed and funneled to a reaction center chlorophyll a: This is a fundamental step in the light-dependent reactions. Chlorophyll and other pigments in the thylakoid membranes absorb light energy and transfer it to the reaction center chlorophyll a. From there, the energy is utilized to drive the flow of electrons and the synthesis of ATP and NADPH.
Based on our analysis, the event that does not occur in the light-dependent reactions of photosynthesis is "Carbon dioxide is incorporated into 3-Phosphoglycerate". This process happens in the light-independent reactions (Calvin cycle) which take place in the stroma of the chloroplasts, not in the thylakoid membranes where the light-dependent reactions occur.