Six tubes containing preparations from animal tissue were set up as shown in the table.
Tube contents
1. glucose + homogenised cells
2. glucose + mitochondria
3. glucose + cytoplasm lacking organelles
4. pyruvic acid + homogenised cells
5. pyruvic acid + mitochondria
6. pyruvic acid + cytoplasm lacking organelles
After incubation, In which three tubes would carbon dioxide be produced?

Options

A. 1, 2 and 3
B. 1, 4 and 5
C. 3, 4 and 6
D. 3, 5 and 6

Answer

To determine in which three tubes carbon dioxide (CO2) would be produced after incubation, we need to analyze the contents of each tube and understand the processes of cellular respiration.

### Step-by-Step Solution:

1. **Understanding the Components of Each Tube:**
- **Tube 1:** Glucose + Homogenized cells
- **Tube 2:** Glucose + Mitochondria
- **Tube 3:** Glucose + Cytoplasm lacking organelles
- **Tube 4:** Pyruvic acid + Homogenized cells
- **Tube 5:** Pyruvic acid + Mitochondria
- **Tube 6:** Pyruvic acid + Cytoplasm lacking organelles

2. **Analyzing Tube 1 (Glucose + Homogenized cells):**
- Homogenized cells contain both cytoplasm and mitochondria.
- Glucose will undergo glycolysis in the cytoplasm to form pyruvic acid, which will then enter the mitochondria for further processing.
- During this process, CO2 will be produced.
- **Conclusion:** CO2 is produced in Tube 1.

3. **Analyzing Tube 2 (Glucose + Mitochondria):**
- Mitochondria require pyruvic acid to produce CO2 through the Krebs cycle.
- Since glucose cannot enter mitochondria directly without glycolysis, no CO2 will be produced here.
- **Conclusion:** CO2 is NOT produced in Tube 2.

4. **Analyzing Tube 3 (Glucose + Cytoplasm lacking organelles):**
- Without organelles, there are no mitochondria or enzymes necessary for glycolysis or the Krebs cycle.
- Therefore, glucose cannot be metabolized to produce CO2.
- **Conclusion:** CO2 is NOT produced in Tube 3.

5. **Analyzing Tube 4 (Pyruvic acid + Homogenized cells):**
- Homogenized cells contain mitochondria, which can process pyruvic acid through the Krebs cycle.
- CO2 will be produced during this process.
- **Conclusion:** CO2 is produced in Tube 4.

6. **Analyzing Tube 5 (Pyruvic acid + Mitochondria):**
- Similar to Tube 4, pyruvic acid can enter the mitochondria and undergo the Krebs cycle, resulting in CO2 production.
- **Conclusion:** CO2 is produced in Tube 5.

7. **Analyzing Tube 6 (Pyruvic acid + Cytoplasm lacking organelles):**
- Again, without organelles, there are no mitochondria or enzymes to process pyruvic acid.
- Thus, no CO2 will be produced.
- **Conclusion:** CO2 is NOT produced in Tube 6.

### Final Conclusion:
The three tubes that produce carbon dioxide after incubation are:
- Tube 1 (Glucose + Homogenized cells)
- Tube 4 (Pyruvic acid + Homogenized cells)
- Tube 5 (Pyruvic acid + Mitochondria)

### Answer:
The correct answer is **1, 4, and 5**.