Final answer:
During the first three reactions of glycolysis, glucose is phosphorylated and rearranged to form a compound ready for cleavage, which is essential for the later production of ATP. No ATP formation, synthesis of glucose, or carbon dioxide release occurs in these steps.
Step-by-step explanation:
During the first three reactions of glycolysis, glucose is changed into a compound that can be readily cleaved. Initially, one molecule of glucose is converted into glucose-6-phosphate through the consumption of one molecule of ATP. Subsequently, the molecule is rearranged to form fructose-6-phosphate, which is then further phosphorylated to fructose-1,6-bisphosphate. This phosphorylation is a crucial step because it destabilizes the sugar molecule, preparing it for cleavage into two three-carbon molecules, each with one phosphate group attached. This stage sets the stage for the subsequent production of ATP and NADH. No ATP is formed at this stage, nor is carbon dioxide released; rather, ATP is consumed.
The overall goal of these early steps is to invest energy to make the later stages of glycolysis more energy-efficient, leading to the eventual release of energy through the synthesis of ATP and the conversion of NAD+ to NADH. Importantly, these steps take place without the release of carbon dioxide and set the stage for the molecule's eventual cleavage.
Therefore, the correct answer to the student's question is 'C) Glucose is changed into a compound that can be readily cleaved.'