O-LevelBiologyRespiration5090/21 · May/June 2020 · Q411 Marks

Explain the importance of the production of carbon dioxide in bread-making.

(a)Explain the importance of the production of carbon dioxide in bread-making.[1]
(b)The diagram shows a flow chart for some of the chemical reactions that occur during bread-making. H starch → maltose → glucose → carbon dioxide + ethanol G Name the processes occurring at G and H. G H[3]
(c)Explain what is causing the changes at G.[3]
(d)(i)State the name of the microorganism used in bread-making and the group of organisms to which it belongs. name group[2]
(d)(ii)State two characteristics of organisms in this group. 1 2[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[1] rise / texture ;
[3] G digestion; H respiration; anaerobic;
[3] amylase; starch to maltose (linked to amylase); maltase; maltose to glucose (linked to maltase);
[2] yeast; fungi;
[2] cell wall; cytoplasm; hyphae / mycelium ; cell nuclei;

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