Questions: Two ATP are invested in glycolysis in order to - add a phosphate group to glucose - join glucose molecules together - release carbon dioxide - break glucose into two molecules - produce acetyl-CoA

The answer is the first one: add a phosphate group to glucose.

Explanation for each option:

1. Add a phosphate group to glucose: This is correct. In glycolysis, two ATP molecules are used to phosphorylate glucose, which helps in destabilizing the glucose molecule and prepares it for subsequent breakdown into two three-carbon molecules.

2. Join glucose molecules together: This is incorrect. Glycolysis involves the breakdown of glucose, not the joining of glucose molecules.

3. Release carbon dioxide: This is incorrect. Carbon dioxide is not released during glycolysis; it is released during the citric acid cycle (Krebs cycle) and oxidative phosphorylation.

4. Break glucose into two molecules: While glycolysis does result in the breakdown of glucose into two molecules of pyruvate, the initial investment of ATP is specifically for adding phosphate groups to glucose, not directly for breaking it down.

5. Produce acetyl-CoA: This is incorrect. Acetyl-CoA is produced from pyruvate during the transition step before entering the citric acid cycle, not directly during glycolysis.

In summary, the two ATP molecules are invested in glycolysis to add phosphate groups to glucose, facilitating its breakdown.