Higher Human | Energy Systems in Muscle Cells

The following links offer some useful revision on Cell Structure to support your learning:

At Higher, you will need to know the following:

Creatine phosphate breaks down to release energy and phosphate that is used to convert ADP to ATP at a fast rate. This system can only support strenuous muscle activity for around 10 seconds, when the creatine phosphate supply runs out. It is restored when energy demands are low
During strenuous muscle activity the cell rapidly breaks down its reserves of ATP to release energy.
Muscle cells have an additional source of energy in creatine phosphate that can be used to replenish ATP pools during rigorous bouts of exercise. This system can only support strenuous muscle activity for around 10 seconds, when the creatine phosphate supply runs out.
When muscle energy demand is low, ATP from cellular respiration is used to restore the levels creatine phosphate.
Lactic acid metabolism. Oxygen deficiency, conversion of pyruvate to lactic acid, muscle fatigue, oxygen debt.
During vigorous exercise, the muscle cells do not get sufficient oxygen to support the electron transport chain. Under these conditions, pyruvate is converted to lactic acid. This conversion involves the transfer of hydrogen from the NADH produced during glycolysis to pyruvic acid to produce lactic acid. This regenerates the NAD needed to maintain ATP production through glycolysis.
Lactic acid accumulates in muscle causing fatigue. Oxygen debt repaid when exercise is complete allows respiration to provide the energy to convert lactic acid back to pyruvic acid and glucose in the liver.
Slow twitch (Type 1) muscle fibres contract more slowly, but can sustain contractions for longer and so are good for endurance activities.
Slow twitch muscle fibres are good for endurance activities like long distance running, cycling or cross-country skiing. Slow twitch muscle fibres rely on aerobic respiration to generate ATP and have many mitochondria, a large blood supply and a high concentration of the oxygen storing protein myoglobin. The major storage fuel of slow twitch muscles fibres is fats.
Fast twitch (Type 2) muscle fibres contract more quickly, over short periods, so are good for bursts of activity.
Fast twitch muscle fibres are good for activities like sprinting or weightlifting. Fast twitch muscle fibres can generate ATP through glycolysis only and have few mitochondria and a lower blood supply than slow twitch muscle fibres. The major storage fuels of fast twitch muscles fibres are glycogen and creatine phosphate. Most human muscle tissue contains a mixture of both slow and fast twitch muscle fibres. Athletes show distinct patterns of muscle fibres that reflect their sporting activities.