Explanation:

To answer this question, we need to understand the preparatory phase of glycolysis and how ATP is utilized.

Preparatory Phase of Glycolysis:
The preparatory phase of glycolysis is the initial step of glucose metabolism. It involves the conversion of one molecule of glucose into two molecules of glyceraldehyde-3-phosphate (G3P). This phase consists of two steps:

1. Hexokinase Reaction:
In this step, glucose is phosphorylated by the enzyme hexokinase, utilizing one molecule of ATP. This reaction converts glucose into glucose-6-phosphate (G6P).

Glucose + ATP → Glucose-6-phosphate + ADP

2. Phosphoglucoisomerase Reaction:
In this step, the enzyme phosphoglucoisomerase converts glucose-6-phosphate (G6P) into fructose-6-phosphate (F6P). This reaction does not consume ATP.

ATP Utilization:
From the above steps, we can see that the first step of the preparatory phase requires one molecule of ATP to convert glucose into glucose-6-phosphate. Since we are considering the breakdown of 12 glucose molecules, the total ATP needed for this step would be:

1 ATP/glucose × 12 glucose = 12 ATP

Therefore, the correct answer is 12 ATP.

However, it is important to note that the preparatory phase only involves the conversion of glucose into two molecules of G3P. The subsequent phase, called the payoff phase, involves the conversion of G3P into pyruvate and produces ATP. In the payoff phase, each G3P molecule generates two molecules of ATP. Since we have 12 glucose molecules, we will have 24 molecules of G3P, which will produce:

2 ATP/G3P × 24 G3P = 48 ATP

Therefore, the total ATP produced in the payoff phase is 48 ATP.

Total ATP Utilization:
To determine the net ATP needed, we subtract the ATP produced in the payoff phase from the ATP consumed in the preparatory phase:

Total ATP = ATP consumed - ATP produced
Total ATP = 12 ATP - 48 ATP
Total ATP = -36 ATP

Since we are asked for the number of ATP needed, the answer should be positive. Therefore, the correct answer is 24 ATP.