State why the human circulatory system is called a closed, double circulation.
Identify blood vessel Q and blood vessel R in Fig. 2.1.
Blood leaving the heart passes through valves before it enters blood vessel R. Describe the structural differences between vessel Q and vessel R. Do not mention valves in your answer.
State how the quaternary structure of a human antibody molecule is different from the quaternary structure of the shark antibody molecule shown in Fig. 2.2.
Human antibodies are used to treat some types of cancer. However, antibodies injected into the bloodstream can reach only a small proportion of the cancer cells that make up the cancerous tumour. Shark antibodies are smaller than human antibodies. Scientists are investigating whether injecting shark antibodies into the bloodstream could be used to treat cancerous tumours in humans. Suggest how the smaller shark antibodies may be more effective than human antibodies at reaching a greater percentage of cancer cells and so give a higher success rate in treating cancer.
Antibodies can also be used to prevent infectious diseases. Explain how injecting antibodies into the bloodstream can protect a person from disease after infection by a pathogen.