8 3 The diagram shows the structure of an animal cell. S Q R P (a) (i) Which of the following is the name of the structure labelled Q? (1) A centriole B nucleus C rough endoplasmic reticulum D smooth endoplasmic reticulum (ii) These cells were cultured in radioactively-labelled amino acids. In which sequence would the cell structures in the diagram become radioactive during protein synthesis? (1) A Q S R B S P R C P R Q D P S R Turn over 9 (iii) Explain one function of lysosomes. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 10 (b) The diagram shows the development of a zygote into a blastocyst. zona pellucida trophectoderm inner cell mass Day 0 = 1 cell Day 1 = 2 cells Day 2 = 4 cells Day 3 = 8 cells Day 4 = 16 cells Day 5 = 32 cells Day 6 = 64 –100 cells The graph shows how the ratio of the volume of the nucleus to the volume of the cytoplasm of each embryonic cell changes as the blastocyst develops. 0 1 2 3 4 5 6 200 180 160 140 120 100 80 60 40 20 0 Time / days Ratio cell of inner cell mass trophectoderm Turn over 11 (i) The ratio shown in the graph can be calculated using the formula ratio = volume of nucleus total volume of cell – volume of nucleus On day 2, the volume of the cell nucleus was 900 μm3. Calculate the total volume of this cell on day 2. Give your answer to two significant figures. (3) Answer .............................................................. μm3 (ii) Comment on the changes in the ratios as the zygote develops into a blastocyst. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 3 = 10 marks) 12 BLANK PAGE