21. Fructose-2,6-bisphosphate

A. activates fructose-1,6-bisphosphatase
B. activates phosphofructokinase
C. inhibits fructose-1,6-bisphosphatase
D. both (b) and (c)

22. Glucose from the breakdown of glycogen is obtained in

A. the liver by phosphorolysis
B. the muscles by phosphorolysis
C. the muscles by hydrolysis
D. both (a) and (b)

23. Glycogen has

A. α-1,4 linkage
B. α-1,6 linkages
C. α-1,4 and α-1,6 linkages
D. α-1,4 and β-1,6 linkage