Question

What do the light-capturing reactions of photosynthesis produce? a. ATP and NADPH b. RuBP c. \(\mathrm{G} 3 \mathrm{P}\) d. glucose

Short answer

The light-capturing reactions of photosynthesis produce ATP and NADPH. Therefore, the correct answer is a. ATP and NADPH.

Step-by-step solution

Option a: ATP and NADPH

ATP (Adenosine Triphosphate) and NADPH (Nicotinamide Adenine Dinucleotide Phosphate) are indeed the products of the light-dependent reactions of photosynthesis. These molecules provide energy and reducing power, respectively, for the light-independent reactions that will take place in the Calvin Cycle to produce glucose and other sugars.

Option b: RuBP

RuBP (Ribulose-1,5-Bisphosphate) is a molecule involved in the Calvin Cycle, which is a part of the light-independent reactions of photosynthesis. Therefore, it is not a correct answer for the products of light-dependent reactions.

Option c: G3P

G3P (Glyceraldehyde-3-Phosphate) is a product of the Calvin Cycle, which is part of the light-independent reactions of photosynthesis. It is not a correct answer for the products of light-dependent reactions.

Option d: Glucose

Glucose is the primary end product of the entire process of photosynthesis, including both the light-dependent reactions and the light-independent reactions (Calvin Cycle). However, glucose is not a direct product of the light-dependent reactions. Based on the analysis of the options, the correct answer is: a. ATP and NADPH

Key concepts

ATP

Adenosine Triphosphate (ATP) is often described as the energy currency of the cell. During the light-dependent reactions of photosynthesis, chlorophyll absorbs solar energy which leads to a chain of reactions resulting in the conversion of ADP and inorganic phosphate into ATP.

The energy stored in ATP is then used throughout the plant cell to power various biological processes, including the Calvin Cycle, which is a major part of photosynthesis. ATP is so crucial that without it, the subsequent steps of synthesizing sugars needed for plant growth and energy storage simply wouldn't occur.

NADPH

Nicotinamide Adenine Dinucleotide Phosphate (NADPH) is another vital molecule produced during the light-dependent reactions. Acting as a reducing agent, NADPH carries electrons and hydrogen ions that are liberated during the splitting of water molecules in a process called photolysis.

This molecule plays a critical role in transferring the energy and electrons necessary for the synthesis of glucose during the light-independent reactions of photosynthesis. Without NADPH, the Calvin Cycle could not synthesize sugars effectively due to the lack of reducing power.

Calvin Cycle

The Calvin Cycle, named after American chemist Melvin Calvin, is part of the light-independent reactions of photosynthesis. It takes place in the stroma of chloroplasts, where it uses the ATP and NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.

The Calvin Cycle involves three main phases: carbon fixation, reduction, and regeneration of RuBP (Ribulose-1,5-Bisphosphate). The cycle must turn three times to produce a single three-carbon G3P (Glyceraldehyde-3-Phosphate) molecule, and six cycles are required to produce one molecule of glucose.

Photosynthetic Energy Conversion

Photosynthetic energy conversion is a process that encompasses both the light-dependent and light-independent reactions. It is the way plants convert light energy from the sun into chemical energy in the form of glucose.

The light-dependent reactions convert solar energy into chemical energy (ATP and NADPH) and occur in the thylakoids. Following this, the light-independent reactions, mainly the Calvin Cycle, utilize that chemical energy to fix carbon dioxide into carbohydrates, the stable form of energy that can be stored and used by organisms. This incredible transformation is fundamental to life on Earth, as it is the basis for the energy transfer through ecosystems.