Following severe skeletal muscle damage (rhabdomyolysis), the oxygen-binding protein myoglobin is released into the bloodstream. It is rapidly filtered by the kidneys and excreted, causing the urine to turn a dark red-brown colour (myoglobinuria).
Which of the following properties of myoglobin explains its ability to pass through the glomerular filtration barrier and enter the renal tubule?
It is a highly hydrophobic protein, allowing it to easily diffuse directly through the lipid bilayers of the podocyte foot processes.
It has a molecular mass of approximately 17,000 Da17,000\text{ Da}17,000 Da, which is well below the filtration threshold of the basement membrane.
It possesses a net negative charge at physiological pH, allowing it to align with the negative charges of the basement membrane.
It lacks a quaternary structure, which permits the protein to unfold and thread through the narrow fenestrations of the capillary endothelium.
