Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Anaerobic respiration is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.
It provides much less energy per glucose molecule than aerobic respiration because the glucose molecule is only partially broken down. Only molecules of are produced per molecule of glucose, compared to in aerobic respiration.
In humans and other mammals, anaerobic respiration occurs during vigorous exercise in muscle cells when the oxygen supply is insufficient. The product is lactic acid ().
The buildup of lactic acid in muscles causes muscle fatigue and cramps, creating an 'oxygen debt'.
Oxygen debt is the extra oxygen required by the body after exercise to react with the accumulated lactic acid and remove it from the cells. The lactic acid is transported to the liver where it is oxidized to and or converted back to glucose.
In yeast and plants, anaerobic respiration is also known as fermentation. The products are ethanol () and carbon dioxide ().
Fermentation in yeast is economically important: is used to make bread rise, and ethanol is used in the production of alcoholic beverages.
📐Formulae
💡Examples
Problem 1:
Explain why a person continues to breathe deeply and quickly for a few minutes after finishing a sprint.
Solution:
This is due to the 'oxygen debt' incurred during the sprint. During high-intensity exercise, muscle cells respire anaerobically to meet energy demands, producing lactic acid ().
Explanation:
The body requires extra oxygen to transport the lactic acid to the liver and oxidize it into and . The deep breathing ensures a high volume of enters the blood to facilitate this aerobic breakdown of lactic acid.
Problem 2:
Compare the energy yield of anaerobic respiration in yeast to aerobic respiration in terms of .
Solution:
Anaerobic respiration: ; Aerobic respiration: .
Explanation:
In the absence of , glucose () is only partially oxidized to ethanol (). Because the bonds in ethanol still hold significant chemical energy, the total energy released and captured as is significantly lower than when glucose is fully broken down to and .