page 04 4. The diagram shows some interactions between amino acid R-groups in a polypeptide chain. Which letter shows hydrophobic interactions? CH2 CH2 CH2 CH2 S S CH2 CH3 CH3 CH3 CH3 CH CH CH2 CH2 CH2 H3N+ O- CH2 OH C CH2 O O- C O C D B A 5. A student is preparing media for an experiment to investigate the effect of an inhibitor on cell growth. Flask 1 contains a control medium with no inhibitor. The concentration of the stock inhibitor solution used to prepare the final solution is 80%. Flask Inhibitor volume (cm3) Glucose volume (cm3) FBS volume (cm3) Buffer volume (cm3) Final inhibitor concentration (%) 1 0·00 1·00 5·00 19·00 0 2 1·00 5·00 20 What volumes of inhibitor and buffer should be added to flask 2 to give 25 cm3 of medium with an inhibitor concentration of 20%? A 4·75 cm3 inhibitor  +  20·25 cm3 buffer B 4·75 cm3 inhibitor  +  14·25 cm3 buffer C 6·25 cm3 inhibitor  +  18·75 cm3 buffer D 6·25 cm3 inhibitor  +  12·75 cm3 buffer