The supply of oxygen (O2) is crucial for life and there are two ways O2 can be carried in blood: dissolved or combined with hemoglobin. Dissolved O2 can only supply a fraction of what the human body needs. One mL blood holds only about 0.003 mL O2 at a partial pressure of oxygen (PO2) of … Continue reading Hemoglobin: a gamechanger
Bird's eggs contain everything that the chick needs, except oxygen. So how exactly does the egg 'breathe'? First, the shell needs to be permeable to gases. The shell consists of a calcium carbonate outer layer, with two shell membranes beneath. A typical outer shell of a hen's egg holds about 10,000 pores, each less than … Continue reading How do eggs breathe?