Question

current cancer research indicates that as some tumours grow, they become deficient in oxygen. how can the cell continue to make atp if oxygen is deficient?

Explanation:

When oxygen is deficient, the electron transport chain (which requires oxygen as the final electron acceptor) is affected. Glycolysis, which is the first step of cellular respiration and does not require oxygen (it is an anaerobic process initially), can still occur. By increasing the rate of glycolysis, the cell can produce more ATP through the anaerobic part of glycolysis (since the later aerobic steps [like the Krebs cycle and electron transport chain] are limited due to lack of oxygen). Strengthening the proton - motive force and increasing the rate of chemiosmosis are related to the electron transport chain (which needs oxygen). Shutting down the electron transport chain does not help in making ATP (as it is a major ATP - producing mechanism in aerobic conditions, but if shut down, the cell needs an alternative, which is increasing glycolysis rate).

Answer:

increasing the rate of glycolysis