Question

Oxygen is consumed in body cells at a rate which is nearly independent of the oxygern concentration. As a model of region in tissue i.e. tumor, consider steady-state oxygen diffusion in a sphere of radius ro, with zeroth-order consumption of oxygen. Assume that oxygen concentration at the outer surface (r - ro) is maintained at constant at Co. Determine the oxygen concentration profile, C(r) If radius ro, and consumption of oxygen is sufficiently large, no oxygen will reach a central core, defined by (r 〈 r). For the central core the assumption of zeroth-order kinetics is no longer valid, because no oxygen is available to react. Determine when an oxygen free central core will exist find an expression for rc. This situation occurs in solid tumors where, as the tumor grows, the cells in the center are deprived of oxygen.

Answer 1

Here the oxygen concentration at the outer surface (r=r₀), and maintained at constant at C_o

We can determine the oxygen concentration Cr is

石D

Cellular respiration uses energy in glucose to make ATP. Aerobic (“oxygen-using”)respiration occurs in three stages: glycolysis, the Krebs cycle, and electron transport. In glycolysis, glucose is split into two molecules of pyruvate. The production of energy requires oxygen. The electron transport chain, where the majority of ATP is formed, requires a large input of oxygen. However, many organisms have developed strategies to carry out metabolism without oxygen or can switch from aerobic to anaerobic cell respiration when oxygen is scarce.

Cancer cells are less differentiated and more adapted to survive under unfavourable conditions and require less oxygen to survive

Cancer cells contain fewer mitochondria, less RER, fewer specialized enzymes

Hypoxic cells- produce lactic acid