Summary
Highlights
Respiration is a chemical process where glucose is broken down to release energy for various cellular processes. This enzyme-controlled reaction occurs in almost all body cells. It's crucial to distinguish respiration from breathing; breathing is the physical act of gas exchange, while respiration is the chemical process of energy release from glucose.
The energy released from respiration is vital for functions such as muscle contraction, protein synthesis, cell division, active transport, growth, nerve impulse transmission, and maintaining a constant body temperature.
An experiment using yeast and glucose solution with methylene blue indicator can demonstrate how temperature affects respiration. The time it takes for the methylene blue to turn colorless indicates the respiration rate. The experiment involves preparing test tubes with yeast, glucose, and indicator, placing them in water baths at different temperatures, and recording the color change time. Controlled variables include the amount of methylene blue, yeast suspension, glucose concentration, and pH.
The rate of respiration increases with temperature up to approximately 40 degrees Celsius, due to increased collisions between enzymes and substrates. Beyond this point, the rate decreases because enzymes begin to denature.
Aerobic respiration is a chemical reaction in cells that uses oxygen to break down nutrient molecules, primarily glucose, to release energy. The word equation is glucose + oxygen → carbon dioxide + water + energy. The balanced chemical equation is C6H12O6 + 6O2 → 6CO2 + 6H2O.
Anaerobic respiration occurs without oxygen, releasing significantly less energy per glucose molecule than aerobic respiration. In yeast, it produces alcohol and carbon dioxide (glucose → alcohol + carbon dioxide), used in bread making and brewing. In muscle cells during vigorous exercise, it produces lactic acid (glucose → lactic acid), leading to muscle cramps and fatigue due to lactic acid buildup.
The temporary oxygen shortage during intense exercise is called oxygen debt. After exercise, increased heart and breathing rates transport lactic acid to the liver, where it reacts with oxygen to produce carbon dioxide and water, repaying the oxygen debt.
Aerobic respiration requires oxygen, produces carbon dioxide and water, and releases a large amount of energy. Anaerobic respiration does not require oxygen; it produces lactic acid in animal cells or carbon dioxide and ethanol in yeast, and significantly less energy.