Question

carbon dioxide cannot diffuse into the blood from an animal cells unless the blood has a blank concentration of carbon dioxide

Answer 1

lower.

substances diffuse from higher to lower concentrations, so the blood would need a lower concentration of carbon dioxide that the cells

Answer 2

The blank can be correctly filled with lower.

Diffusion refers to passive movement of molecules or substances from the region of higher concentration to the region of lower concentration.

Thus, if carbon dioxide has to diffuse out of the cell into the blood then, carbon dioxide concentration or partial pressure of carbon dioxide should be lower as compared to that of the cell.

The partial pressure of the carbon dioxide is higher in cells as it produced as byproduct of cellular respiration.