Applied anatomy physiology: Energy systems (Aerobic system)

Amount of ATP created during aerobic respiration

38 ATP per glucose mol

Adenosine Triphosphate (ATP)

the only usable form of energy in the body. Enables muscle contractions to take place. Consists of one molecule of adenosine and three phosphates

How ATP is created

created by three energy systems: aerobic, anaerobic (ATP-PC system and glycolytic). The energy derived from foods is broken down to release energy that is used to form ATP.

How energy is released from ATP

Energy is released from ATP by breaking the bonds between the phosphate groups using enzymes (ATP-ase). When the bond is broken, ATP loses a phosphate group and becomes ADP, alongside an inorganic phosphate (Pi).

Breakdown of ATP formula

ATP -> ADP + P + energy

What fuels chemical reaction in muscle cells

food (carbs, fats and protein) or phosphocreatine found in muscles.

What affects energy system used

Intensity of exercise and duration - different for each sport and some may need longer energy systems.

Three stages of aerobic system

glycolysis, krebs cycle, electron transport chain

intensity of aerobic system

low/medium, where O2 is readily available.

Duration of aerobic system

Glycogen stores in muscles enables you to work up to 2 hours.

Aerobic system fuel source

glucose

Fatiguing by-products of aerobic system

None

Glycolysis definition

The breakdown of glucose into pyruvic acid

Glycolysis explanation

Occurs in the sarcoplasm of the muscle cell. For every molecule of glucose undergoing glycolysis, a net of two molecules of ATP is formed. Before pyruvic acid produced can enter next stage (KC), it splits into two acetyl groups and is then carried into the Krebs cycle by coenzyme A.

Krebs cycle definition

A series of cyclical chemical reactions that take place using oxygen in the matrix of the mitochondria.

Krebs cycle explained

Acetyl Co-A combines with oxaloacetic acid, forming citric acid. Carbon and hydrogen are given off, with the carbon forming Carbon dioxide which is transported to lungs and breathed out, and the hydrogen taken to the electron transport chain. Two molecules of ATP are produced as a result of this.

Beta oxidation definition

A process where fatty acids are broken down to generate acetyl-CoA, which enters the Krebs cycle.

Beta oxidation explanation

Stored fat is broken down into glycerol and free fatty acids for transportation by the blood. These are then converted in Acetyl-CoA, which follow the same path as glycogen metabolism. More ATP can be made from one molecule of fatty acids than one molecule of glucose - which is why it is used for long duration, low-intensity exercise.

Electron transport chain

Involves a series of chemical reactions in the cristae of the mitochondria where hydrogen is oxidised to water and 34 molecules of ATP are produced.

Advantages of the Aerobic System

More ATP can be produced, there are no fatiguing by-products and lots of glycogen and triglyceride stores so exercise can last for a long time.

Disadvantages of aerobic system

Complicated system - can't be used straight away as it takes a while for enough O2 to become available to meet demands of activity and ensure glycogen and fatty acids are completely broken down. Fatty acid transportation to muscles is low and requires 15% more O2 to be broken down than glycogen.