A-LevelBiologyCell structure9700/21 · May/June 2021 · Q69 Marks

Lysosomes are cell structures that contain enzymes known as acid hydrolases. Fig. 6.1 shows some processes that occur in animal cells. [Figure 6.1]

(a)Name the cell structures labelled A and E. A ........................................................................................................................................ E ........................................................................................................................................[2]
(b)State the function of the structures labelled F.[1]
(c)Name the process by which bacteria are taken into the cell at C.[1]
(d)With reference to the processes occurring at B and at D in Fig. 6.1, outline the role of acid hydrolases in lysosomes.[3]
(e)Carrier proteins in the membranes of lysosomes maintain a lower pH than the surrounding cytoplasm by moving hydrogen ions. Suggest how the carrier proteins maintain the lower pH within the lysosomes.[2]

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Mark scheme

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

[2] A rough endoplasmic reticulum ;
E Golgi, body / apparatus / complex;
[1] transport from, (R)ER / ribosomes, to Golgi ; A from A to E
A transport from Golgi to, cell surface membrane / phagosome
A separate, acid hydrolases / enzymes, from, rest of cell / AW
[1] phagocytosis / endocytosis ;
[3] any three from
1 break down / digest / destroy, bacteria / pathogen(s) ;
2 break down / digest / destroy, (worn out / defective / AW), organelles / named organelle (in animal cell) ; A autophagy
3 catalyse / speed up, hydrolysis ;
4 any two named substrates ;
e.g. (any named) polysaccharides / proteins / (phospholipids / (named) nucleic acids
5 idea that recycle / reuse, biological molecules within cell ;
6 (macrophage / phagocyte) cut up to present antigen ;
[2] moves / pump(s), hydrogen ions / protons, into the lysosome against concentration gradient ;
active transport / uses ATP / energy from respiration / ref to conformational change of carrier ;
R if a ref to facilitated diffusion

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