Glucose, Labeled with ¹⁴C in Different Carbon Atoms, Is Added

Multiple Choice

Glucose, labeled with ¹⁴C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of ¹⁴CO₂ will occur when the glucose is labeled in:

A) C-1.
B) C-3.
C) C-4.
D) C-5.
E) C-6.