Respiration

A chemical process that involes the breakdown of nutrient molecules and glucose in order to release the energy stored within the bonds of these molecules.

— Respiration is enzyme controlled.

Aerobic Respiration

Aerobic respiration requires oxygen and is defined as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

Complete breakdown of glucose to release relatively large amount of energy for use in cells.

Produces carbon dioxide and water.

Glucose + Oxygen → Carbon Dioxide + Water

$C_6H_{12}O_6+6O_2→6CO_2+6H_2O$

Anaerobic Respiration

Anaerobic respiration does not require oxygen and is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.

Anaerobic Respiration in Animal

When exercising vigorously, muscle have a higher demand for energy than resting or exercising. Our body can only deliver a limited amount of oxygen to muscle cells for aerobic respiration. Therefore, some glucose is broke down into lactic acid.

Glucose → Lactic Acid

• Lactic Acid then builds up in muscle cells and lowers pH of cells — more acidic.
  • It could denature the enzymes in cells, so it has to be removed.
• Cells excrete lactic acid into blood, when blood pass through liver, lactic acid is taken up into liver cells where it is oxidised producing CO2 and Water.
  • This is the reason we continue breathing heavily and heart rates remain high after finishing exercise. “Repaying the oxygen debt.”
    • We need to transport the lactic acid from muscles to the liver, and continue getting larger amounts of oxygen into the blood to oxidise the lactic acid.

Anaerobic Respiration in Yeast

Yeast is used for bread making, where carbon dioxide produced causes dough to rise. In brewing, the ethanol produced gives beer its alcoholic nature - the CO2 produced gives beer its fizzy condition.

Glucose → Alcohol + Carbon Dioxide

$C_6H_{12}O_6→2C_2H_3OH+2CO_2$