Lab Notes and Procedures-07 Biology 1004

North Arkansas College

Topic: Fermentation and Respiration 

(Experiment 6)

  1. All living organisms get their energy from the breakdown of carbohydrates.
  2. This energy is most commonly produced by enzyme reactions and metabolic pathways.
  3. Glucose is the most common nutrient utilized to make energy. Other carbohydrates (sugars) are converted to glucose if it is not present (e.g. sucrose, fructose, lactose, maltose).
  4. Glucose is converted in absence of oxygen (anaerobically) to pyruvic acid by the process of glycolysis. In this process, a net of 2 ATP is produced.

Glucose - pyruvic acid.
  1. Under anaerobic conditions, pyruvic acid is converted to lactic acid (muscle, liver) or lactic acid and ethanol (yeast and bacteria) by the process of fermentation.

Absence of 02 - lactic acid & ethanol

This is a very energy inefficient process (net of 2 ATP).

  1. If the pyruvic acid is allowed to enter mitochondria where oxygen is available, it enters the Kreb’s Cycle (citric acid cycle). A number of acid intermediates are produced, CO2 and electrons (H+). The H+ is transferred through respiratory chain and makes 3 ATP of energy. This process of energy production using oxygen is called respiration.
  2. One molecule of glucose passes through glycolysis to combine with 02 during respiration and produces a net of 36 ATP.

Fermentation - conversion of glucose to pyruvic acid » lactic acid & ethanol in absence of 02.

Lab Project
  1. Grape juice - warmed to 30-35°C. Add 10 ml of activated yeast (yeast with water). Hook up to low pressure sensor on computer. Measure carbon dioxide given off through fermentation and glycolysis.
  2. Need 100 ml of grape juice, 10 ml of yeast, graph the CO2 as kPa (partial atmospheric pressure).
  3. Run Respiration Experiment as indicated in the Lab Book.

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