During anaerobic respiration in yeast, pyruvate is converted into which of the following substances?

RRB Nsg. Superintendent-2026 (Shift -3rd)

Biochemistry & Nutrition

Easy

Appeared in: RRB Nsg. Superintendent-2026 (Shift -3rd)

Explanation

In the absence of oxygen, yeast undergoes a process called alcoholic fermentation.
During this process, pyruvate (from glycolysis) is broken down into ethanol and carbon dioxide.
This pathway allows the regeneration of NAD+ from NADH, which is necessary for glycolysis to continue producing a small amount of ATP.
This specific metabolic pathway is unique to yeast and some other microorganisms.

Option A: Lactic acid is produced during lactic acid fermentation, which occurs in animal muscle cells and certain bacteria, not in yeast.
Option B: Glucose is the initial reactant for respiration, and oxygen is required for aerobic respiration. They are not products of anaerobic respiration.
Option C: Carbon dioxide and water are the final products of aerobic respiration, a process that involves the complete oxidation of glucose in the presence of oxygen.

Visual 1: Flowchart - A flowchart illustrating the two main steps of alcoholic fermentation: pyruvate being converted to acetaldehyde (releasing CO2) and then acetaldehyde being converted to ethanol.
Visual 2: Diagram - A comparative diagram showing the pathways of alcoholic fermentation in yeast versus lactic acid fermentation in muscle cells, highlighting the different end products.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anaerobic respiration in yeast (alcoholic fermentation) as background academic context rather than a clinical decision trigger.
Understanding different metabolic pathways is crucial. While alcoholic fermentation is not a human process, the related pathway, lactic acid fermentation, is clinically significant. Excess lactate production leads to lactic acidosis, a serious condition seen in shock, sepsis, and intense physical exertion.
The products of yeast fermentation are central to several industries. In baking, the carbon dioxide produced makes bread rise. In brewing and winemaking, the ethanol produced is the alcoholic component of the beverage.
What if the question asked about anaerobic respiration in bacteria? The answer would vary widely. Different bacteria have diverse fermentation pathways, producing substances like acetic acid (vinegar), butyric acid, and acetone, in addition to lactic acid and ethanol.

How to Approach the Question

First, identify the key terms in the question: 'anaerobic respiration', 'yeast', and 'pyruvate'.
Recall that 'anaerobic' means 'without oxygen'.
Access your knowledge about cellular respiration. Remember that there are two main types of anaerobic respiration (fermentation): alcoholic and lactic acid.
Associate 'yeast' with 'alcoholic fermentation'.
Recall the specific products of alcoholic fermentation, which are ethanol and carbon dioxide.
Evaluate the options to find the one that matches your recalled knowledge and eliminate the others based on their association with different processes (lactic acid fermentation, aerobic respiration, or photosynthesis).

Concept Tested & Keywords

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