Which set of terms most accurately describes the pathway taken by a molecule of `CO_(2)` from the atmosphere to the point where it enters the calvin cycle ?

Options

A. stomatal aperture, inter cellular space, mesophyll cell, chloroplast
B. stomatal aperture, epidermal cell, mesophyll cell, chloroplast
C. stomatal guard cell, intercellular space, mesophyll cell membrane, chloroplast
D. stomatal guard cell, intercellular space, phloem serve tube, chloroplast

Answer

To determine the pathway taken by a molecule of carbon dioxide (CO₂) from the atmosphere to the point where it enters the Calvin cycle, we can break down the steps as follows:

### Step-by-Step Solution:

1. **Entry through Stomata**:
- Carbon dioxide enters the leaf through small openings called stomata. These are located on the surface of the leaves and are surrounded by guard cells that regulate their opening and closing.

2. **Stomatal Aperture**:
- The specific opening of the stomata is referred to as the stomatal aperture. This is the first point of entry for CO₂ from the atmosphere into the leaf.

3. **Diffusion into Intercellular Space**:
- Once CO₂ enters through the stomatal aperture, it diffuses into the intercellular spaces within the leaf. These spaces allow for the movement of gases between the stomata and the mesophyll cells.

4. **Mesophyll Cells**:
- The CO₂ then moves into the mesophyll cells, which are the primary sites of photosynthesis within the leaf. These cells contain chloroplasts where the photosynthetic reactions occur.

5. **Chloroplasts**:
- Finally, the CO₂ enters the chloroplasts within the mesophyll cells. The chloroplasts are the organelles where the Calvin cycle takes place, using CO₂ to synthesize glucose.

### Summary of the Pathway:
The pathway taken by a molecule of CO₂ from the atmosphere to the point where it enters the Calvin cycle can be summarized as:
- **Stomatal Aperture → Intercellular Space → Mesophyll Cell → Chloroplast**