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Cardiff International School Dhaka (CISD) Lost Class Make Up Assignment Class: A2/A3 Subject: Chemistry Date: 22nd (Sunday)-28th (Saturday) February 2015 Total Mark- 20 Instructions: All of your assignment must be done in A4 size paper. Mention your Name, Class, Roll and Section clearly on the top sheet of your assignment. Submission Deadline: Saturday 28th February 10.00 AM to the respective subject teacher. The deadline is strict. Name:................................................................................................................................................. Class: .........................Roll: ........................ Sec: .................. Teacher: ...................................... Sunday-Saturday 22-28 February 2015 Lesson: 28.5 Factors affecting enzyme activity Task: Study – i. Difference between competitive and non-competitive inhibitor ii. Effect of temperature on enzyme activity iii. Effect of pH on enzyme activity iv. Chemical denaturation v. Cofactors: prosthetic groups and coenzymes Worksheet/Exercise: Q1. (a) Describe three differences between a competitive inhibitor and a non-competitive inhibitor. [3] (b) Thallium is a heavy metal. i. Write an equation to show the reaction of thallium (I) ions, TI+, with the sulfhydryl group in a cysteine residue. [2] ii. What type of inhibitors are thallium (I) ions? Explain. [2] Q 2. (a) Sketch a graph to show how the activity of an enzyme varies with temperature. [3] (b) Explain the shape of the graph in terms of kinetic theory and the effect of temperature on the integrity of the enzyme’s structure. [3] (c) Sketch a graph to show how pH affects the activity of a neutral protease. [3] (d) Explain the shape of the graph in terms of changes taking place in the region of the enzyme’s active site. [4] Text Book/Reference Book: Chemistry Coursebook, Page No. 417 - 421, Chapter – 28 Answer Keys: Q1.(a) For example: A competitive inhibitor has a similar shape and distribution of charge to the normal substrate. On the other hand, a non-competitive inhibitor doesn’t have a similar shape to the normal substrate. (b) Heavy metals (Ag, Hg, TI), ions react with one or more sulfhydryl groups, replacing the hydrogen atom with a metal ion. Q2. (a) At temperatures between 0o C and about 40 o C the rate of enzyme activity increases with temperature. Enzyme activity decreases markedly above 40 o C. (b) As temperature increases the molecules move faster, a greater proportion of the molecules collide etc. (c) Extremes of pH denature enzymes by disrupting their tertiary structure. Most enzymes are active over a narrow pH range. (d) The activity of some enzymes depends on particular amino acid residues at the active site being charged, or not being charged. In these cases, a shift of pH by even 1 unit change can change the enzyme activity significantly. Help Lines: For any assistance, please contact Chemistry Teacher: Jobaida Akther, [email protected] Principal Head of School: G.M.Nizam Uddin, +88-01622181818, [email protected]