I need help with 3 and 4 3. Tumors typically lack an extensive capillary network

Question

I need help with 3 and 4

3. Tumors typically lack an extensive capillary network and often must keep functioning under reduced oxygen supply. Studies have shown that tumor cells often have glycolytic rates ten times higher than normal cells. Explain why this is true. What type of medical diagnostic procedure can be done to detect the presence of tumors in the body utilizing this biochemical concept? 4. During strenuous exercising, skeletal muscle tissues produce the needed ATP only by glycolysis. During strenuous exercise, acidosis sometimes occurs which results in muscle soreness and a loss of muscle function. Why is lactate produced under these conditions? What chemical process causes the acidosis?

Explanation / Answer

3. The glycolytic pathway proceeds without requirement of oxygen. It is the process in which glucose is catabolised to derive ATP and pyruvic acid. Tumor cells lack an extensive capillary network which results in limited supply of oxygen. But glycolysis produces only 2 effective ATP molecules by breaking down of glucose per cycle. This results in increased rate of glycolysis in tumor cells to meet the energy requiremnts.

The presence of marked glucose molecules in PET scan can be helpful in detection of tumor. As the increased rate of glycolysis requires more number of glucose molecules, using radioactive carbon molecules can help.

4. After the production of pyruvic acid, there is net gain of 2ATP along with 2 molecules of NADH. If glycolysis is only carried out in muscle cells, there will be a shortage of NAD+ molecules which will terminate the gkycolysis. In order to maintain a regular supply of NAD+ molecules, the enzyme lactate dehydrogenase converts pyruvate into lactic acid while oxidising NADH to NAD+. When lactic acid is present in larger amount then it causes acidosis. Acidosis occurs due to limted supply of oxygen in muscle cells leading to production of lactate.

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