During rhabdomyolysis (severe muscle injury), the protein myoglobin is released from damaged muscle tissue into the blood and subsequently excreted in the urine, giving it a characteristic dark brown colour.
Which of the following properties of myoglobin primarily explains how it is able to pass through the glomerular filtration barrier into the kidney tubule?
Myoglobin is highly soluble in blood plasma due to its hydrophilic outer surface
Myoglobin has a molecular mass of approximately 17,000 Da17,000\text{ Da}17,000 Da
Myoglobin lacks a quaternary structure and exists purely as a single polypeptide chain
Myoglobin contains a negatively charged heme group that is actively attracted to the podocyte filtration slits
17 exam-style questions on OCR A A Level Biology Excretion as an example of homeostatic control. Each one has a worked solution and a mark scheme showing where the marks go.