10. Infectious diseases
A section of Biology, 9700
Listing 10 of 290 questions
Tuberculosis (TB) is an infectious disease caused by a bacterium. In the majority of people, only the lungs are affected. In most cases, the transmission of TB from an infected person to an uninfected person involves Mycobacterium tuberculosis. A different species of bacterium is involved in the transmission of TB from cattle, such as dairy cows, to humans. Name the species of bacterium causing the transmission of TB from dairy cows to humans. In some areas, cattle cannot be regularly tested or treated for TB. In these areas, milk and dairy products from infected dairy cattle may enter the human food chain. Outline a control measure that can be taken to protect people that consume milk and dairy products from these infected cattle. Cattle are not usually affected by M. tuberculosis, but the pathogen can cause disease in other animals. A few cases of transmission of TB from people to animals have been reported. Explain the most likely mode of transmission of TB from an infected person to an animal. In most people, the response of the immune system to the infection of lung tissue by M. tuberculosis can prevent the spread of the bacterium to other organs of the body. The bacterium is contained in the lungs in a dormant state. This is known as latent TB. Outline the treatment that is used to kill M. tuberculosis in latent TB infections. M. tuberculosis can spread in the blood and lymph to other organs in the body. In very rare cases, a disease known as mycotic aneurysm can be caused by infection of the arterial wall, particularly in elastic arteries. The damage caused by the pathogen can lead to a rupture of the artery. With reference to the structure of the wall of elastic arteries, suggest how damage caused by M. tuberculosis infection can lead to the rupture of the artery. You may draw a diagram if you wish. Space for diagram
9700_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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The infectious disease cholera is caused by a bacterium. shows a transmission electron micrograph of this bacterium. ×30 000 Name the bacterium that causes cholera. The bacterium in is an example of a prokaryotic cell. Each of the descriptions A to C describes a cell structure found in prokaryotic cells and in plant cells. For each of the descriptions A to C: • name the cell structure described • state one difference in this structure between a prokaryotic cell and a plant cell. A the site of polypeptide synthesis cell structure difference B the genetic material of the cell cell structure difference C the structure that provides a rigid shape to the cell and prevents osmotic lysis cell structure difference Cholera is an example of an infectious disease. Explain what is meant by an infectious disease. The symptoms of cholera are caused by choleragen, a toxin released by the bacterium. Choleragen is a protein made up of six polypeptides: • a single copy of a polypeptide known as the A subunit that includes an extended alpha helix • five polypeptides that together make the B subunit. The B subunit of choleragen binds to a cell surface membrane component, known as GM1, of an intestinal epithelial cell. The complete choleragen protein then enters the cell by endocytosis. Once inside the cell, the A subunit of the protein acts as an enzyme, disrupting the normal functioning of the cell. List the levels of protein structure present in choleragen. Outline the mechanism by which choleragen enters the cell. You may use the space for annotated diagrams. Using genetic engineering, it is possible to produce a form of choleragen consisting of only subunit B. This can be combined with inactivated bacterial cells to produce a vaccine against cholera. Suggest why subunit B, rather than subunit A, is used in the vaccine. Outline how this vaccine can give protection against cholera.
9700_m17_qp_22
THEORY
2017
Paper 2, Variant 2
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Questions Discovered
290