Biology 9700 · AS & A Level · The gas exchange system

The gas exchange system — practice question

Certain tissues in the gas exchange system contain cells that are able to make and release mucins. These mucins are kept in vesicles inside the cells, ready to be secreted. After they leave the cell, mucins absorb water and form mucus.
(a)[2]

Name the structures in the gas exchange system that make and secrete mucins.

(b)[1]

Mucins are described as glycosylated proteins. Glycosylation is the addition of sugar components after polypeptides are synthesised. Suggest one cell location where glycosylation of mucin could take place.

(c)[2]

The processes involved in making and secreting mucins are given here: translation, exocytosis, glycosylation, transcription. Finish Table 2.1 by arranging the processes in the order in which they occur.

(d)[3]

Chloride ions move out of the mucin-producing cells at the same time as mucin is secreted. Suggest and explain how the loss of chloride ions helps mucin to form mucus.

(e)[3]

The gas exchange system contains some cells that can divide by mitosis. Explain why having these cells in the gas exchange system is important.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: mucous gland cells or mucous glands

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