Question

The following molecules can be found at various stages during cellular respiration:

I. acetyl-CoA
II. carbon dioxide
III. glucose
IV. glyceraldehyde(G3P or PGAL)
V. pyruvate
Which of the following sequences represents the above molecules in order from the largest to the smallest amount of chemical energy?
a. II,I,V,IV,III
b. III,IV,V,I,II
c. III,IV,I,V,II
d. III,I,V,IV,II
e. IV,III,II,I,V

Answer 1

The correct order from the largest to the smallest amount of chemical energy is Glucose (III), Glyceraldehyde (G3P or PGAL) (IV), Pyruvate (V), Acetyl-CoA (I), and Carbon dioxide (II), making option b the correct answer.

Step-by-step explanation:

The question asks for the order of molecules from the largest to the smallest amount of chemical energy during cellular respiration. The correct sequence, considering the amount of energy they carry from highest to lowest, is as follows: Glucose → Glyceraldehyde (G3P or PGAL) → Pyruvate → Acetyl-CoA → Carbon dioxide. Therefore, the answer is b. III, IV, V, I, II.

Glucose (III) is a six-carbon molecule with the highest amount of chemical energy. During glycolysis, glucose is broken down into two molecules of Glyceraldehyde-3-phosphate (IV, commonly referred to as G3P or PGAL), each carrying energy. The G3P is further oxidized to produce Pyruvate (V), which carries less energy than G3P. Pyruvate is then decarboxylated and combined with coenzyme A to form Acetyl-CoA (I), with a further loss of energy. Finally, through the Krebs cycle, Acetyl-CoA is oxidized to form Carbon dioxide (II), which has the least amount of chemical energy among the listed molecules.