14 Catabolism Lab

Aerobic respiration is much more efficient than fermentation, but needs Oxygen, as CO₂ (and H₂O) is released in the citric acid cycle.

THE EFFECTS OF TEMPERATURE ON THE RATE OF FERMENTATION
1. Alcohol fermentation: C₆H1₂O₆ -> 2CH₃CH₂OH + 2CO₂ + energy; CO₂ is released as pyruvate is converted to acetaldehyde.
2. Yeast fermentation of sucrose at 3 (not 4) different temperatures for 60 minutes.
  Each group needs 75 ml sucrose + 30 ml yeast, divided equally into 3 fermentation tubes.
  Make 1 batch of the yeast solution for the whole class: multiply above measures by number of groups.
  Note: set oven temperature to low - do not overheat the racks.
3. Measure amount of CO₂ released into top of fermentation tube.
MEASURING THE RATE OF OXYGEN CONSUMPTION p. 116
Use Electrolytic Respirometer to measure rate of aerobic respiration.
SKIP.
EFFECTS OF ACTIVITY ON RESPIRATION RATES IN HUMANS p. 117
Cellular respiration releases CO₂ as one of its products, together with heat.
Carbon dioxide forms carbonic acid in water: CO₂ + H₂O -> H₂CO₃: this will be measured.
Use Phenolphthalein as pH indicator: colorless in acid, pink in neutral or basic (alkaline) solutions.
Use 0.5% NaOH to make 100 ml. standard solution with a light - medium pink color. Divide this 100 ml. into 2 flasks - one will be your standard, and the other will be the experimental flask.