2018 Collated Biomolecules & Enzymes STQ MS.pdf

2018 Collated Biomolecules and Enzymes (DNA, Gene Expression) 2018 / H2 / AJC PRELIM / P2 Q11Fig. 1.1 shows the effect of pH on the activity of a protease enzyme at the optimal temperature of 37oC. Fig. 1.1(a)Draw, on Fig. 1.1, the approximate shape of the curve if the same experiment is conducted at 25oC.Similar shape to Fig. 1.1 but lower than curve in Fig. 1.1;[1](b)Explain with reasons the shape of the curve you have drawn.At lower temperature, lower kinetic energy of molecules;Less effective collisions between enzyme and substrates, less enzyme-substrate complex formation per unit time / lower rate of enzyme-substrate complex formation;[2]

(c)Using information from the graph, explain why proteases stored in vesicles with pH 7.2 cannot break down vesicular membrane proteins and suggest how these proteases can be activated through increase in pH.(At least one)With low activity of just 200 U/ml, enzyme is inactive at pH 7.2;Optimal enzyme activity of 900 U/ml (accept reasonable figure quoted, correct units quoted) is highest at pH 9;At pH 9 (accept argument at pH 7.2): charges on acidic and basic R-groups altered;Contact and catalytic residues has the correct charge to catalyse the reaction at pH 9 (accept converse);R-group interactions such as ionic and hydrogen bonds are altered;Tertiary structure / 3D conformation / configuration of enzyme is that of an active enzyme;Active site shape is complementary to shape of substrate;Maximum rate of enzyme-substrate complex formation;[max 4m](At least one)pH can be increased to optimum pH by pumping of H+ ions out of the vesiclesVesicle membrane has proton pumps;[6][Total: 9]

2018 / H2 / EJC PRELIM / P2 Q1 ( Cancer Eukaryotic Cell Structure)2The synthesis of collagen is shown in Fig. 1.1. ACProcess B(tropocollagen)Fig. 1.1(a)(i)Describe two important functions of structure A in the synthesis of collagen. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ...…………………………………………………………………………………………………[2]Structure A is the nuclear pore;

1.Allows mature mRNA to leave nucleus and enter cytosol for translation into collagen by ribosom2.Allows RNA polymerase/ ribonucleotides to enter nucleus to synthesise mRNA/tRNA durtranscription of collagen gene;3.Allows exit of mRNA to ribosomes to be translated; 4.Allows tRNA to leave nucleus for amino acid activation/ amino acid attachment for use translation during collagen synthesis;(any 2)(ii)Tropocollagen leaves the cell to be assembled to form collagen fibrils via Process B. OutProcess B. ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………[3]1.Process B is exocytosis;2