What increase in concentration of chemical decreases the frequency of sickling cells?

 

Increase in the concentration of O2.

Step-by-step explanation

Blood or RBC genetic disorders, or hemoglobinopathies, are sickle cell diseases such as sickle cell anemia. Individuals with sickle cell disease have defective genes that instead of normal HbA, create abnormal haemoglobin (Hb) named HbS. This HbS induces sickling episodes.

Cell sickling refers to the change in the normal form of RBC due to polymerization into a sickle-like shape. Certain conditions such as cold, inflammation, exhaustion, acidosis, low oxygen or hypoxia intensify the sickling of cells. Generally speaking, HbS and HbA are close in solubility. But HbS becomes less soluble under hypoxic conditions, causing further sickling.

Thus the addition of oxygen would decrease the sickling frequency.

Thus, addition of oxygen will reduce the frequency of sickling.