Final answer:
Photosynthesis is an endothermic reaction that requires energy from the sun to create glucose. The transformation of glucose into starch, a combination reaction, is typically exothermic as it releases energy.
Step-by-step explanation:
Is Photosynthesis Endothermic or Exothermic?
Photosynthesis is indeed an endothermic reaction, as it requires the absorption of energy from the sun to convert carbon dioxide and water into glucose and oxygen. The energy is provided by sunlight and temporarily stored in ATP and NADPH, which are then used to synthesize glucose. When plants convert the glucose into starch, it's through a process of dehydration synthesis, a type of combination reaction where many glucose molecules join together, releasing water in the process. This reaction is generally considered to be exothermic because it releases energy, usually in the form of heat, as chemical bonds are formed in the larger starch molecule.
Formation of Starch from Glucose
During the storage of glucose as starch, there is a transformation of energy. While the exact energetics can vary, generally the formation of starch from glucose is exothermic because energy is released when the chemical bonds are formed. Thus, in the transition from glucose to starch, there is both a combination of smaller molecules into a larger one and a release of energy. This energy can dissipate into the surroundings or be used by the plant for other processes.