A-LevelBiologyInfectious diseases9700/22 · Oct/Nov 2023 · Q59 Marks
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.
- (a)Name the species of bacterium causing the transmission of TB from dairy cows to humans.[1]
- (b)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.[1]
- (c)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.[2]
- (d)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.[2]
- (e)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 (bursting) 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.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [1] Mycobacterium bovis ; A M. bovis
- [1] pasteurising / drinking pasteurised, milk; I vaccines / antibiotics
- [1] A heat treatment of / sterilise / boil, milk I cook milk
- [1] A use pasteurised milk to make dairy products
- [1] A meat from (deceased dairy) cattle should be cooked, thoroughly / AW
- [2] (infected), person, coughs / breathes (out) / talks / sneezes / AW, and (uninfected) animal, inhales / inspires / breathes in ;
- [2] aerosol / droplet, infection / transmission A transmitted by aerosol
- [2] or organism/pathogen / bacteria / M. tuberculosis, in, airborne droplets / droplets in air ; A contaminated, airborne droplets / droplets in air
- [2] any two from: antibiotics / antibacterials ; I vaccines / vaccination
- [2] detail; e.g. combination treatment/combination of antibiotics I many antibiotics A many different antibiotics allow ecf e.g. if stated as drugs for mp1
- [2] named antibiotics; e.g. rifampicin / isoniazid / rifampentine / moxifloxacin / pyrazinamide / ethambutol accept other correct
- [2] four months – 12 months ; accept range or stated months allow 'must take for 6 months to more than 12 months' as this has noted a time less than 12 months
- [2] shorter time using combination than single antibiotic ;
- [3] any three from: allow elastic tissue for elastic fibres
- [3] 1 loss of/damage to, elastic fibres (and smooth muscle) from tunica media ; A scar tissue replaces, elastic fibres / smooth muscle, in tunica media A middle layer for tunica media
- [3] 2 loss of/damage to, collagen (fibres), in / damage to, tunica, externa / adventitia ; A outer layer for tunica, externa / adventitia
- [3] mp1 and mp2 if layers not named, use diagram to confirm location of elastic fibres in (thicker) middle layer and collagen fibres in (thinner) outer layer
- [3] any two from mp3-5 ; 3 cannot withstand, high pressure / increase in pressure / pressure of blood ;
- [3] 4 overstretching / over-expansion / described ; A cannot, stretch / expand
- [3] 5 impaired / poor / no / AW, recoil ; in context of loss of elastic fibres
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →