Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Fermentation is a form of anaerobic respiration that involves the incomplete oxidation of glucose under anaerobic conditions (absence of ).
The process takes place entirely in the cytoplasm of the cell.
In alcoholic fermentation, pyruvic acid () is converted into ethanol () and in a two-step process catalyzed by the enzymes pyruvic acid decarboxylase and alcohol dehydrogenase.
In lactic acid fermentation, certain bacteria and animal muscle cells (during vigorous exercise) convert pyruvic acid into lactic acid () using the enzyme lactate dehydrogenase.
A crucial step in both types of fermentation is the re-oxidation of back to , which allows glycolysis to continue in the absence of oxygen.
The energy released during fermentation is very low; less than of the energy in glucose is released, and the net gain is only 2 molecules of per molecule of glucose.
Yeast poisons themselves to death when the concentration of alcohol reaches about .
📐Formulae
💡Examples
Problem 1:
Calculate the net gain of when 5 molecules of glucose undergo fermentation in a yeast cell.
Solution:
10
Explanation:
In fermentation, one molecule of glucose yields a net gain of 2 molecules (produced during glycolysis). Therefore, for 5 molecules of glucose: .
Problem 2:
Name the enzymes involved in the conversion of pyruvic acid to ethanol and identify the byproduct released.
Solution:
Enzymes: Pyruvic acid decarboxylase and Alcohol dehydrogenase; Byproduct: .
Explanation:
Pyruvic acid () first undergoes decarboxylation to form acetaldehyde and via pyruvic acid decarboxylase. Then, acetaldehyde is reduced to ethanol by alcohol dehydrogenase using .