Oxygen debt

Briefly explain how an oxygen debt arises and how the body deals with it (96B8)

Exercise

During heavy exercise, energy consumed is consistently above that can be provided by aerobic metabolism.

The difference is made up by anaerobic metabolism of carbohydrates to lactate.

Lactate accumulation appears to be the limiting factor for sustained heavy work.

Lactate is produced and diffuse out of skeletal muscle cells and removed by increased blood flow.

Lactate in skeletal muscle cells causes drop in intracellular pH and can cause distress at levels above 11mmol/L (10 times normal).

After exercise, O2 consumption remains above the resting level

=> repayment of oxygen debt

=> related to the level of lactate at the end of exercise.

This increased O2 consumption is used to get extra O2 for

oxidation of the accumulated lactate (to CO2 and water)
- 80% of lactic acid is converted to glycogen
- 20% of lactic acid is metabolised to CO2 and H2O.
restoration of oxygen stores
replenish ATP (via oxidative phosphorylation), phosphorylcreatine, and oxymyoglobin

Need to answer (1) how does oxygen debt arise (2) how does body deal with it
need to explain how when O2 is scarce, the energy needs of cells are derived by a diversion from glycolysis and oxidative phosphorylation to production of lactate
(extra) details of energy source of cells in aerobic and anaerobic metabolism
(extra) oxygen sources and reserves
outline of how O2 and ATP are replenished
outline how accumulated lactate is elimiated by reversal of glycolytic pathway using diversions at 2 irreversible steps, and by conversion to pyruvate and processing through Krebs cycle
(extra) why O2 is required for elimination of lactate

elimination of lactate and why O2 is required to eliminate lactate

O2 stores and sources

glycogen