Question

Which one of the following is secreted by the yeast for fermentation?
A. Enolase
B. Invertase
C. Zymase
D. Dehydrogenase

Answer 1

Hint: Enzymes are commonly known as the biological catalysts are large protein molecules and are responsible for speeding up the chemical reaction taking place within a biological cell.

Complete answer:
Yeast is a single-celled fungus that contains a number of enzymes useful during fermentation. Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. Let us analyse each given option to find out the correct answer.

Option a: Enolase is an enzyme that catalyzes a reaction of glycolysis. Enolase is involved in the catalysis of the conversion of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP), the ninth and penultimate step of glycolysis. Therefore, this is an incorrect option.

Option b: Invertase is an enzyme that is commonly used to make candy liquid centers, chocolate, fondant candies, creme eggs, etc. It is usually derived from yeast, either from bread factories or beer breweries. Invertase is also found in human saliva. It is produced by the bacteria, Streptococcus mutans. Therefore, this is an incorrect option.

Option c: Zymase catalyses the fermentation of sugar into ethanol and carbon dioxide. It occurs naturally in Yeasts. Zymase, an enzyme that can convert glucose to ethanol. This is known as alcoholic fermentation. The zymase acts on glucose and leads to the production of ethanol and carbon dioxide. Brewers yeast and wine yeast contain zymase, an enzyme that can convert glucose to ethanol. Therefore, this is the correct option.

Option d: Dehydrogenase is intracellular enzymes that catalyze oxidation-reduction reactions. It oxidizes a substrate by reducing an electron acceptor, usually $NAD^+$/$NADP^+$ or a flavin coenzyme such as FAD or FMN. Therefore, this is an incorrect option.

Thus, the correct option is C, Zymase.

Note: It is to be noted that alcohol fermentation occurs in micro-organisms such as yeast and converts glucose to energy, and carbon dioxide is released. The resultant by-product is called ethanol (also known as ethyl alcohol or simply alcohol). Lactic acid fermentation occurs in certain bacteria, yeast, and muscle cells and converts glucose to energy. Its by-product is lactate.