Respiration

Uses of energy in living organisms

Muscle contraction
Protein synthesis
Cell division
Active transport
Growth
Nerve impulses
Maintenance of a constant body temperature

Aerobic respiration

Aerobic Respiration - the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

Glucose + oxygen -> carbon dioxide + water (+ energy, ATP)
C6H12O6 + 6O2 -> 6CO2 + 6H2O
ATP - Energy is stored in a chemical compound, Adenosine Triphosphate (ATP). Breaking down this releases energy to be used by the body.

Anaerobic respiration

Anaerobic respiration - the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.

It releases a smaller amount of energy in cells compared to Aerobic Respiration. Glucose is not completely broken down, so much less energy is released.

During vigorous exercise

Glucose -> energy + lactic acid

In plants and yeast

Glucose -> carbon dioxide + ethanol + energy
C6H12O6 -> 2C2H5OH + 2CO2

When exercising:

Muscles contract more than usual -> require more energy. Cells in muscle perform aerobic respiration to release energy
Heart rate also increases, causing us to inhale more/deeper

Lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt and heavy breathing. Quick heart rate will transport lactic acid from muscle to liver. Continuation of deeper and faster breathing to supply oxygen for aerobic respiration of lactic acid, until all lactic acid is used up. Lactic acid converts to glucose and CO2.