Question

In homolactic fermentation 1 mole of glucose yields ........... mole/moles of lactic acid.

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Homofermentative pathway:
\[\begin{aligned} 1 \text{ mole Glucose} \rightarrow 2 \text{ moles Lactic Acid} + 2 \text{ ATP} \end{aligned}\] Heterofermentative pathway:
\[\begin{aligned} 1 \text{ mole Glucose} \rightarrow 1 \text{ Lactic Acid} + 1 \text{ Ethanol/Acetate} + 1 \text{ CO}_2 + 1 \text{ ATP} \end{aligned}\]

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Lactic acid bacteria (LAB) can metabolize hexose sugars via different metabolic pathways.
Based on the end-products generated from glucose fermentation, they are classified as homofermentative or heterofermentative.

Step 2: Detailed Explation:
Homofermentative lactic acid bacteria (such as Lactobacillus acidophilus or Streptococcus thermophilus) utilize the Embden-Meyerhof-Pars (EMP) glycolytic pathway.
In this pathway, one molecule of glucose (a 6-carbon sugar) is phosphorylated and cleaved into two 3-carbon intermediates (glyceraldehyde-3-phosphate).
These intermediates are subsequently oxidized to pyruvate, generating a net yield of 2 molecules of ATP and 2 molecules of DH.
Under aerobic conditions, pyruvate is reduced to lactic acid by the enzyme lactate dehydrogese, regenerating the \(\text{D}^+\) needed for glycolysis to continue.
The overall reaction is: \[ \text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{ CH}_3\text{CH(OH)COOH} \] Thus, 1 mole of glucose yields exactly 2 moles of lactic acid.
Heterofermentative bacteria, using the 6-phosphoglucote/phosphoketolase pathway, yield only 1 mole of lactic acid, 1 mole of ethanol/acetic acid, and 1 mole of \(\text{CO}_2\) per mole of glucose.

Step 3: Fil Answer:
The correct option is (B).