Respiration Notes

Respiration in Cells

• Respiration is a chemical process breaking down nutrient molecules (glucose) to release energy.
• It's enzyme-controlled and occurs with (aerobically) or without (anaerobically) oxygen.
• Aerobic respiration releases more energy per glucose molecule than anaerobic respiration.
• Occurs in all living cells, with most aerobic reactions in the mitochondria.
• Energy released is used for muscle contraction, protein synthesis, cell division, growth, active transport, nerve impulses, and maintaining body temperature.

Effect of Temperature on Respiration (Yeast)

• Methylene blue dye indicates the rate of aerobic respiration in yeast; discoloration measures respiration rate.
• Independent variable: temperature.
• Dependent variable: respiration rate (measured by time for methylene blue to discolor).
• Controlled variables: dye volume/concentration, yeast suspension volume/concentration, glucose concentration, and pH.
• Optimal temperature is up to 40°C.
• Above 40°C, enzymes denature, decreasing respiration rate.

Aerobic Respiration

• Requires oxygen to break down nutrient molecules to release energy.
• Complete glucose breakdown yields a large amount of energy, $CO_2$, and water.
• Word equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy
• Balanced Chemical Equation: $C<em>6H</em>{12}O<em>6 + 6O</em>2 \rightarrow 6CO<em>2 + 6H</em>2O$

Anaerobic Respiration

• Does not require oxygen; breaks down nutrient molecules to release energy.
• Incomplete glucose breakdown yields less energy than aerobic respiration.
• Produces different products based on the organism.

Anaerobic Respiration in Animals

• Occurs in muscle cells during vigorous exercise.
• Glucose is broken down into lactic acid.
• Word equation: Glucose → Lactic Acid + Energy

Anaerobic Respiration in Yeast

• Used in bread making (carbon dioxide causes dough to rise) and brewing (ethanol gives beer alcoholic nature, carbon dioxide gives it fizz).
• Word equation: Glucose → Ethanol + Carbon Dioxide + Energy
• Balanced Chemical Equation: $C<em>6H</em>{12}O<em>6 \rightarrow 2C</em>2H<em>5OH + 2CO</em>2$

Anaerobic Respiration & Oxygen Debt

• Lactic acid build-up lowers pH, potentially denaturing enzymes.
• Lactic acid is transported to the liver, where it's oxidized into carbon dioxide and water (aerobic respiration).
• Heavy breathing and high heart rate after exercise help transport lactic acid and increase oxygen for oxidation, repaying the 'oxygen debt'.