A-LevelBiologyCell structure9700/21 · Oct/Nov 2021 · Q111 Marks

Fig. 1.1 is a transmission electron micrograph of cells from the leaf of a plant. [Figure 1.1]

(a)(i)Name the cell structures X, Y, and Z. X Y Z[3]
(a)(ii)State two ways in which the structure of an animal cell differs from plant cells such as those shown in Fig. 1.1. 1 2[2]
(b)(i)Cell structure Y in Fig. 1.1 contains a large starch granule (grain). Name the chemical reagent used to test for starch and state the colour change that will be seen if starch is present. reagent colour change[2]
(b)(ii)Starch granules contain amylose and amylopectin. Describe the similarities and differences between the structure of amylose and the structure of amylopectin.[4]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[3] X nucleus ;
Y chloroplast ;
Z vacuole ;
[2] any two from: no, large / permanent, vacuole / (temporary) small vacuoles ;
this is in context of large permanent vacuole
no, chloroplast/ chloroplasts;
no cell wall;
no plasmodesmata ;
glycogen granules or no, starch, granules / grains ;
nucleus, (more) central / AW; A nucleus not at, periphery / edge, of cell
centrioles (present);
AVP; e.g. fewer Golgi bodies
[2] iodine solution; A iodine in potassium iodide solution / I in KI solution
(change in colour from) orange / brown, to, blue / black / purple ;
[4] any four from: similarities to max 3 polymers / polysaccharides / described ;
composed of α-glucose ;
(monomers joined by) glycosidic bonds ;
contain 1-4 (glycosidic) bonds / linkages ; A glucosidic
differences to max 3 amylose molecules are unbranched / amylopectin molecules are branched ;
amylopectin molecules contain 1–6 (glycosidic) bonds ;
amylose helical;
amylose is a smaller molecule ;
amylopectin is more compact;

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