Fig. 1 shows a simplified cross-section through a human alveolus. A bacterium has entered the lungs of a patient with pneumonia. White blood cells leave a c...
Question 1 Report
Fig. 1 shows a simplified cross-section through a human alveolus. A bacterium has entered the lungs of a patient with pneumonia. White blood cells leave a capillary and move towards the bacteria. Oxygen still diffuses from the air space into blood cells.
(a) Name the cells that can produce antibodies. [1]
(b) Describe how antibodies help defend the patient against bacteria. [2]
(c) Suggest why a serious lung infection can lower the amount of oxygen entering the blood. [2]
A dentist uses Fig. 1 to show why brushing teeth matters. The drawing shows bacteria in plaque on the surface of a tooth near the gum. The bacteria use sugar from food and produce acid. Over time, acid can damage the hard outer layer of the tooth.
(a) Name the hard outer layer of a tooth. [1]
(b) Suggest why eating sugary snacks many times each day increases tooth decay. [2]
(c) Use the figure to describe how brushing lowers the number of bacteria in the mouth. [2]
Answer Details
Labelled answer diagram:
Lung infection, (a) Lymphocytes are the cells that produce antibodies. [1]
Lung infection, (b) Antibodies bind to specific antigens on bacteria. This can make bacteria clump together or mark them so that phagocytes can recognise and destroy them. [2]
Lung infection, (c) A serious infection may fill alveolar air spaces with fluid or mucus. This reduces the surface available for diffusion or increases the diffusion distance, so less oxygen enters the blood. [2]
Teeth, (a) The hard outer layer of a tooth is enamel. [1]
Teeth, (b) Frequent sugary snacks give plaque bacteria repeated supplies of sugar. The bacteria produce acid more often, so enamel is damaged more frequently and tooth decay becomes more likely. [2]
Teeth, (c) Toothbrush bristles remove plaque from the tooth surface. The bacteria are removed along with the plaque, lowering their number in the mouth. [2]
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