Question

What is the correct order of events that happen during the catabolism (break down) of glucose in the absence of O2? A) Glycolysis, Krebs cycle, Electron transport chain B) Glycolysis, Fermentation, Krebs cycle C) Krebs cycle, Glycolysis, Fermentation D) Electron transport chain, Fermentation, Glycolysis

Answer 1

Step-by-step explanation:

The correct order of events that happen during the catabolism (breakdown) of glucose in the absence of oxygen (anaerobic conditions) is:

B) Glycolysis, Fermentation, Krebs cycle

Here's a brief explanation of each step:

1. **Glycolysis:** This is the first step in glucose breakdown and occurs in the cytoplasm. Glucose is split into two molecules of pyruvate, producing a small amount of energy and some molecules called ATP and NADH.

2. **Fermentation:** In the absence of oxygen, cells undergo fermentation. Fermentation comes in different types, such as lactic acid fermentation or alcoholic fermentation, depending on the organism. During fermentation, pyruvate is converted into either lactic acid or ethanol, regenerating NAD+ to keep glycolysis going.

3. **Krebs Cycle (Citric Acid Cycle):** The Krebs cycle occurs in the mitochondria when oxygen is available. Pyruvate produced during glycolysis can enter the Krebs cycle to generate more ATP and other high-energy molecules.

Option B reflects the order of events in the absence of oxygen, which is glycolysis followed by fermentation.