Biology 9700 · AS & A Level · Infectious diseases

Infectious diseases — practice question

Several species in the genus Plasmodium are known to infect humans and cause malaria. Plasmodium has a complicated life cycle with several distinct structural forms. One form of the pathogen found in human hosts is the merozoite.
(a)[1]

State the kind of organism that causes malaria.

(b)[1]

State the difference in appearance between the red blood cell shown in Fig. 4.1 and a healthy red blood cell.

(c)[1]

When Plasmodium is found inside mature red blood cells, the concentration of haemoglobin in these infected cells falls. Suggest why the haemoglobin concentration inside the infected red blood cells decreases.

(d)[4]

MSP1 consists of one polypeptide, which is encoded by gene $MSP1$. Table 4.1 describes some of the stages involved in MSP1 synthesis by Plasmodium. These stages are not in the right order. Use the steps in Table 4.1 to complete Table 4.2 and show the correct sequence of events in MSP1 synthesis.

(e)[4]

The MSP1 protein shows three levels of structure: primary, secondary and tertiary. Outline the changes that take place after translation in a polypeptide such as the MSP1 polypeptide, leading to a protein with secondary and tertiary structure.

(f)[4]

Subunit vaccines contain non-self antigens but not whole organisms. Their purpose is to stimulate a primary immune response after the vaccine is administered so that the person gains artificial active immunity. One trial done on human volunteers has used MSP1 from Plasmodium falciparum in a subunit vaccine against malaria. Explain why a vaccine containing MSP1 gives artificial active immunity to malaria.

(g)[3]

The female Anopheles mosquito acts as the vector of Plasmodium. Discuss the ways in which the vector is controlled to help prevent malaria transmission.

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