What is the primary function of glycogen phosphorylase in glycogen metabolism?

• A. It breaks down glycogen by removing glucose subunits as free glucose.
• B. It converts glucose 1 phosphate to glucose 6 phosphate.
• C. It synthesizes glycogen by adding glucose subunits.
• D. It breaks down glycogen by removing glucose subunits as glucose 1 phosphate.

Answer: (D)