Answer:
(1) Oxidative metabolism increase. As oxidative metabolism increases, there is less need for glycolytic products to enter oxidative phosphorylation hence this limits entry into oxidative metabolism
(2) Oxidative metabolism is limited. As oxidative metabolism is decreased, there is increased need for glycolytic products to enter the oxidative phosphorylation to produce more ATP hence this promotes entry into oxidative metabolism.
(A) Low O2 level, PDK active. As PDK is active, pyruvate dehydrogenase is phosphorylated and inactivated, thus limiting entry into oxidative metabolism.
(B) High O2 level, active PDH. With high o2, there is increased final electron acceptors in oxidative phosphorylation hence there is increased rate of oxidative metabolism and thus entry is promoted, as acetyl CoA is used up at a faster rate.
C) High O2 level, PDK inhibitor present. PDK inhibitor activates PDH hence entry is promoted.
(D) High O2level, inactive PDH. PDH inactive hence entry is limited.
(E) High O2 level, active PDK. PDH inactivated by PDK hence entry is limited. although if you consider anaplerotic reactions into TCA cycle, the entry through other means may not be limited.