Fig. 1.1 shows the structure of the amino acid glycine. [Figure 1.1]

1. (a)(i)Name the parts of the amino acid molecule labelled A and B in Fig. 1.1. A B [2]
2. (a)(ii)Amino acids are monomers used to build proteins. Complete Fig. 1.2 by drawing a diagram to show the formation of a peptide bond between two molecules of glycine. [Figure 1.2][3]
3. (b)Plasma cells synthesise and secrete antibodies. Fig. 1.3 is a transmission electron micrograph showing a plasma cell. [Figure 1.3]
4. (b)(i)Use a label line and the label T on Fig. 1.3 to identify where the genes coding for the polypeptide chains of the antibodies are located.[1]
5. (b)(ii)Calculate the actual diameter of the plasma cell shown by the line P–Q. Write down the formula used to make your calculation. Show your working and give your answer to the nearest micrometre (μm). formula actual diameter = μm[2]
6. (b)(iii)The plasma cell in Fig. 1.3 is very metabolically active. Suggest why there are very few mitochondria visible in the electron micrograph in Fig. 1.3.[1]
7. (c)Sieve tube elements in plants have very few organelles such as mitochondria. Explain how having very few organelles is an adaptation of the sieve tube element to its function.[2]

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