This element is "evolved" during the light-dependent reactions.
HIF [hiff] transcription factors are activated by low concentrations of this element. The Warburg [VAR-burg] effect explains how low concentrations of it make tumor cells acidic. VEGF [vedge-F], secreted by tumor cells when this element is sparse, stimulates vasculo-genesis. Low concentrations of this element stimulate the reduction of (*) pyruvate, rather than the formation of oxaloacetate. This element is "evolved" during the light-dependent reactions. It is the final acceptor in the electron transport chain. Lack of this element favors formation of lactate in anaerobic fermentation. For 10 points, name this element required for cellular respiration, which is absorbed in the lungs.
HIF [hiff] transcription factors are activated by low concentrations of this element.
oxygen [or O]