<P> Oxygen binds with red blood cells in the blood stream . The oxygen affinity with hemoglobin on red blood cell surfaces enhances this bonding ability . In a system of facilitated diffusion of oxygen, there is a tight relationship between the ligand which is oxygen and the carrier which is either hemoglobin or myoglobin . This mechanism of facilitated diffusion of oxygen by hemoglobin or myoglobin was discovered and initiated by Wittenberg and Scholander . They carried out experiments to test for the steady - state of diffusion of oxygen at various pressures . Oxygen - facilitated diffusion occurs in a homogeneous environment where oxygen pressure can be relatively controlled . For oxygen diffusion to occur, there must be a full saturation pressure (more) on one side of the membrane and full reduced pressure (less) on the other side of the membrane i.e. one side of the membrane must be of higher concentration . During facilitated diffusion, hemoglobin increases the rate of constant diffusion of oxygen and facilitated diffusion occurs when oxyhemoglobin molecule is randomly displaced . </P> <P> Glucose is a six - carbon sugar that provides energy needed by cells . Since glucose is a large molecule, it is difficult to be transported across the membrane through passive diffusion Hence, it diffuses across membranes through facilitated diffusion, down the concentration gradient . The carrier protein at the membrane binds to the glucose and alters its shape such that it can easily to be transported from one side of the membrane to the other . Movement of glucose into the cell could be rapid or slow depending on the number of membrane - spanning protein . It is transported against the concentration gradient by a dependent glucose symporter which provides a driving force to other glucose molecules in the cells . Facilitated diffusion helps in the release of accumulated glucose into the extracellular space adjacent to the blood capillary . </P> <P> Carbon monoxide has a facilitated diffusion process similar to that of oxygen . They both make use of the high affinity of hemoglobin and myoglobin for the gas . Carbon monoxide also combines with hemoglobin and myoglobin with the help of facilitated diffusion just as it is in oxygen but the rate at which they react differs from one another . Carbon monoxide has a dissociation velocity which is 100 times less than that of oxygen; its affinity for myoglobin is 40 times higher and 250 times higher for hemoglobin, compared to oxygen . </P>

What type of solute molecules are moved by facilitated diffusion