Final answer:
The additive that provides a physical barrier to prevent glycolysis is Sodium fluoride (D). It inhibits enzymes involved in glycolysis, preserving blood glucose levels unlike EDTA, heparin, or sodium citrate which are anticoagulants but do not specifically inhibit glycolysis. The correct option is D.
Step-by-step explanation:
The additive that provides a physical barrier to prevent glycolysis is D. Sodium fluoride. Sodium fluoride acts as an inhibitor of the enzymes that catalyze glycolysis, the metabolic pathway responsible for breaking down glucose to generate energy.
By inhibiting these enzymes, it prevents blood cells from using glucose, thus preserving blood glucose levels and stopping glycolysis.
While EDTA and sodium citrate work as anticoagulants by chelating calcium ions, they are not specifically inhibitors of glycolysis.
Heparin also acts as an anticoagulant by a different mechanism. However, sodium fluoride is particularly used in glucose blood tests because of its efficiency in halting glycolysis, ensuring accurate measurement of blood glucose levels. The correct option is D.