What is the function of ribulose-5-phosphate? (a) to be oxidized to generate NADPH (b) to be used in nucleotides (c) to be used in transaldolase and transketolase reactions (d) to be used as NADH shuttle between cytosol and mitochondria (e) to be used by two isomerases to balance the ratios of pentose phosphates in the cytosol .