Which of the following is NOT a product of the light reaction?

Choice A reason: Biuret test is a test for the presence of proteins or peptides in a solution. It involves adding Biuret reagent, which is a blue solution of copper (II) sulfate and sodium hydroxide, to the solution. If proteins or peptides are present, they form a complex with the copper (II) ions, which changes the color of the solution to violet or pink. ³

Choice B reason: Gram's iodine test is a test for the presence of starch in a solution. It involves adding iodine solution, which is a brown solution of iodine and potassium iodide, to the solution. If starch is present, it forms a complex with the iodine molecules, which changes the color of the solution to blue-black. ⁴

Choice C reason: Ninhydrin test is a test for the presence of amines or amino acids in a solution. It involves adding ninhydrin reagent, which is a purple solution of ninhydrin, to the solution. If amines or amino acids are present, they react with ninhydrin to produce a purple color, often called Ruhemann's purple. ¹

Choice D reason: Brown paper test is a test for the presence of lipids, such as fats or oils, in a solution. The test involves placing a drop of the solution on a piece of brown paper and letting it dry. If lipids are present, they leave a translucent spot on the paper, which can be seen by holding the paper against a light source. The test is based on the fact that lipids are nonpolar and do not dissolve in water, but can dissolve in organic solvents and stain the paper. ²

Choice E reason: Benedict's test is a test for the presence of reducing sugars, such as glucose or maltose, in a solution. The test involves adding Benedict's reagent, which is a blue solution of copper (II) sulfate, sodium carbonate, and sodium citrate, to the solution and heating it in a water bath. If reducing sugars are present, they reduce the copper (II) ions to copper (I) ions, which form a red, orange, or green precipitate of copper (I) oxide. ⁵

Photosynthesis is the process by which plants, algae, and some bacteria use light energy to convert water and carbon dioxide into organic molecules, such as glucose, that can be used as food or building blocks for other molecules. Photosynthesis also releases oxygen as a by-product, which is essential for aerobic respiration in animals and other organisms.

Photosynthesis is the primary source of energy and organic matter for most living organisms on Earth, either directly or indirectly. Directly, photosynthesis provides food for the primary producers, such as plants and algae, that make their own food. Indirectly, photosynthesis provides food for the consumers, such as animals and fungi, that eat the primary producers or other consumers.

Photosynthesis also affects the global climate and the carbon cycle by removing carbon dioxide from the atmosphere and storing it in organic matter. Therefore, photosynthesis is the most important metabolic pathway of living organisms because its products have a significant impact on the biosphere.