Fermentation worksheet - Free Printable

Absolutely! Let’s solve each part step by step, explaining the biochemical reactions involved.

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1. Reactions in Mitochondria to Generate ATP (Aerobic Respiration)

This refers to aerobic cellular respiration, which occurs in mitochondria and includes the Krebs cycle and electron transport chain (ETC). The overall reaction for aerobic respiration is:

> Glucose + Oxygen → Carbon Dioxide + Water + ATP

But since the question asks for reactions *in mitochondria*, we focus on the final stages: after glycolysis, pyruvate enters mitochondria, gets converted to Acetyl CoA, then goes through Krebs cycle, and finally ETC produces ATP using oxygen.

However, the most common summary equation taught for mitochondrial ATP production (combining all steps) is:

> C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (≈30-32 ATP per glucose)

But note: Glucose is broken down in cytoplasm first. The mitochondria mainly handle:

- Pyruvate oxidation → Acetyl CoA
- Krebs cycle → CO₂, NADH, FADH₂
- ETC → H₂O + ATP (using O₂ as final electron acceptor)

Since the diagram has 5 boxes (2 reactants → 3 products), we can represent the overall mitochondrial contribution using the simplified version of aerobic respiration:

✔ Answer for #1:
```
Glucose + Oxygen → Carbon Dioxide + Water + ATP
```

*(Note: Technically, glucose isn’t metabolized entirely inside mitochondria — but this is the standard summary equation used in education to represent mitochondrial ATP generation from respiration.)*

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2. Lactic Acid Fermentation

This occurs in muscle cells or some bacteria when oxygen is low (anaerobic conditions). Glycolysis produces pyruvate, which is then reduced to lactic acid to regenerate NAD⁺ so glycolysis can continue.

The reaction is:

> Pyruvate + NADH → Lactic Acid + NAD⁺

So, only one molecule (pyruvate) is converted into lactic acid with the help of NADH (which becomes NAD⁺).

✔ Answer for #2:
```
Pyruvate → Lactic Acid + NAD⁺
```

*(Note: NADH is consumed, not shown as a product — but often in simplified diagrams, it's implied. Since there are only 3 boxes, we show pyruvate going to lactic acid and NAD⁺.)*

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3. Alcohol Fermentation

This occurs in yeast and some plants under anaerobic conditions. Pyruvate is converted to ethanol (alcohol) and carbon dioxide, regenerating NAD⁺.

The two-step process:
1. Pyruvate → Acetaldehyde + CO₂
2. Acetaldehyde + NADH → Ethanol + NAD⁺

Combined, it’s:

> Pyruvate → Ethanol + Carbon Dioxide + NAD⁺

✔ Answer for #3:
```
Pyruvate → Ethanol + Carbon Dioxide + NAD⁺
```

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## ✔ Final Answers:

1. Mitochondrial ATP Generation:

```
Glucose + Oxygen → Carbon Dioxide + Water + ATP
```

2. Lactic Acid Fermentation:

```
Pyruvate → Lactic Acid + NAD⁺
```

3. Alcohol Fermentation:

```
Pyruvate → Ethanol + Carbon Dioxide + NAD⁺
```

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## 🧠 Explanation Summary:

- Mitochondria use oxygen to fully break down glucose (via Krebs & ETC) to make lots of ATP.
- Lactic acid fermentation happens in muscles without oxygen — turns pyruvate into lactic acid to keep glycolysis going.
- Alcohol fermentation happens in yeast — turns pyruvate into ethanol and CO₂, also to recycle NAD⁺.

These processes allow cells to produce ATP even without oxygen — just less efficiently than aerobic respiration.

Let me know if you’d like the chemical formulas or diagrams too!