Question

The cye relies heavily on the metabolism of glucose but different parts of the eye use glucose differently. Which of the following statements is/are correct? A. The retina uses glucose primarily by aerobic glycolysis and the TCA cycle. B. The cornea uses over half its glucose via the hexose monophosphate pathway. C. The lens has the glycolytic pathway but not the hexose monophosphate pathway. D. The role of glutathione reductase is to inactivate active oxygen species. E. All of the above.

Short answer

a. The retina uses glucose primarily by aerobic glycolysis and the TCA cycle. b. The cornea uses over half its glucose via the hexose monophosphate pathway. c. The lens has the glycolytic pathway but not the hexose monophosphate pathway. d. The role of glutathione reductase is to inactivate active oxygen species. e. All of the above. Answer: E. All of the above (since Statements A, B, and D are correct).

Step-by-step solution

Statement A: The retina uses glucose primarily by aerobic glycolysis and the TCA cycle.

This statement is TRUE. The retina is a highly metabolically active tissue, and its cells are dependent on the availability of glucose to meet their energy needs. The retina mainly consumes glucose through aerobic glycolysis and the TCA cycle to produce ATP, the cell's primary energy source.

Statement B: The cornea uses over half its glucose via the hexose monophosphate pathway.

This statement is also TRUE. The cornea's primary source of energy is glucose, and it utilizes the hexose monophosphate pathway (also called the pentose phosphate pathway) to generate NADPH and ribose-5-phosphate. The NADPH produced in this pathway plays a vital role in the cornea's defense against oxidative stress and protection from damage caused by UV radiation.

Statement C: The lens has the glycolytic pathway but not the hexose monophosphate pathway.

This statement is FALSE. The lens, like the cornea, also uses both the glycolytic pathway and the hexose monophosphate pathway for glucose metabolism. The lens relies on both these pathways to generate ATP, maintain its transparency, and protect itself from oxidative stress.

Statement D: The role of glutathione reductase is to inactivate active oxygen species.

This statement is TRUE. Glutathione reductase is an enzyme that plays a crucial role in protecting cells from oxidative damage by reducing the oxidized form of glutathione (GSSG) to its reduced form (GSH). GSH then acts as an antioxidant by inactivating reactive oxygen species generated during cellular metabolism, thus preventing harm to cellular components. Based on the analysis of the statements, the correct answer is:

Answer

E. All of the above (since Statements A, B, and D are correct).