To study mammalian lung structure and perfusion, a researcher prepared a tissue section containing pulmonary capillaries. They used two fluorescent dyes: Dye A, which selectively binds to double-stranded DNA, and Dye B, which targets an abundant oxygen-binding conjugated protein found within the capillaries.
Explain why Dye A shows no fluorescence in mature mammalian red blood cells. Identify the oxygen-binding protein targeted by Dye B.
The researcher also investigated the alveolar structure in healthy lungs and lungs damaged by chronic inflammatory fibrosis. They calculated the surface area to volume ratios for these alveoli. Some of their results are shown in the table below:
| Alveolar condition | Surface area / μm2\mu\text{m}^2μm2 | Volume / μm3\mu\text{m}^3μm3 | Surface area:volume ratio |
|---|---|---|---|
| Healthy | 1.8×1051.8 \times 10^51.8×105 | 5.6×1055.6 \times 10^55.6×105 | __________ |
| Damaged (Fibrosis) | __________ | 6.4×1056.4 \times 10^56.4×105 | 0.045:10.045:10.045:1 |
Complete the table. State your calculated surface area and surface area:volume ratio to 2 significant figures.
Chronic inflammatory fibrosis causes the deposition of excess collagen fibers in the alveolar walls, making them thicker, and can also lead to the destruction and merging of alveolar spaces. Other than a reduced surface area to volume ratio, describe one physical change in the structure of these damaged alveoli. Explain how this change would affect the rate of gas exchange.
