2018 Collated Biomolecules & Enzymes MCQ QP+MS

2018 Biomolecules and Enzymes MCQ2018 / H2 / ACJC PRELIM / P1 Q41Proteins can be categorised as globular or fibrous, depending on their structure. How many of the following statements describes fibrous proteins only?1Monomers are linked by peptide bonds formed during translation2Long molecules which are insoluble in water3Helical molecules consisting of non-repeating sequences of amino acids4Contains hydrogen bonds between polypeptidesA0B1C2D32018 / H2 / ACJC PRELIM / P1 Q52Malic acid is produced by a series of enzyme-catalysed reactions. The addition of malonic acid results in an accumulation of succinic acid, a near absence of both fumaric acid and malic acid, and has no effect on the concentration of oxoglutaric acid.Further addition of fumaric acid results in the formation of malic acid.What does this information indicate about malonic acid?AIt is an inhibitor of enzyme 1.BIt catalyses the formation of succinic acid.CIt is an inhibitor of enzyme 2.DIt reacts with fumaric acid.

2018 / H2 / AJC PRELIM / P1 Q23Which diagram shows the linking of two monomers together to form cellulose? 2018 / H2 / AJC PRELIM / P1 Q34The diagram shows the structure of a lipid molecule. Which statements are not correct?1The fatty acid occupying the central (second) position of the lipid molecule has a molecular formula of C16H32O2, while the fatty acid occupying the other two positions has a molecular formula of C18H34O2.2More ATP can be obtained from the lipid molecule than equal mass of glycogen.

3The molecule is able to dissolve in an aqueous medium due to the presence of polar bonds.4The molecule increases fluidity of membranes as it contains a kink.A1 and 4B2 and 3 C3 and 4D1, 3 and 4 2018 / H2 / AJC PRELIM / P1 Q55Human hair is made up from bundles of a fibrous protein called keratin, which is similar to collagen.The diagram shows the folded structure of keratin polypeptide chain, which forms the basic unit of hair fibre structure. When hair is wet, it can lengthen temporarily due to the breaking of bonds in the folded keratin polypeptide chain. When it dries, the hair gradually returns to its original length.What are broken to produce this length of the keratin chain structure?Apeptide bondsBdisulfide bondsChydrophobic interactionsDhydrogen bonds

2018 / H2 / AJC PRELIM / P1 Q66The diagram shows the effect of increasing substrate concentration on the rate of an enzyme-catalysed reaction at different concentrations of an inhibitor of the enzyme. Which statements correctly explain the results of this investigation?1The inhibitor is a competitive inhibitor. 2The inhibitor is a non-competitive inhibitor. 3Adding 0.1% inhibitor lowers the effective enzyme concentration by altering enzyme tertiary structure, therefore the maximal rate of reaction cannot be restored at high substrate concentration.4Increasing inhibitor concentration results in the inhibitor being able to compete effectively with the substrate molecules to form more enzyme – inhibitor complexes, therefore higher concentration of inhibitor leads to rate of reaction not reaching maximum at high substrate concentration. A1 and 4B1 and 3C2 and 3D2 and 4

2018 / H2 / DHS PRELIM / P1 Q37Lipid membranes can be formed in the laboratory by painting phospholipids over a support (PTFE sheet) with a hole in it. Such a lipid membrane is impermeable to water-soluble materials including charged ions such as Na+ or K+. In one experiment with Na+ ions, no current flowed across the membrane until a substance called gramicidin was added.Which statement is consistent with this information and your knowledge of membrane structure?Gramicidin becomes incorporated into the membrane and is ________________.Aa carbohydrate molecule found only on the outside of the membrane.Ba non-polar lipid which passes all the way through the membrane.Ca protein molecule with both hydrophilic and hydrophobic regions.Da protein molecule which has only hydrophobic regions.2018 / H2 / DHS PRELIM / P1 Q48Which of the following is / are TRUE of triglycerides and phospholipids?1Both contain glycerol.2Both are not amphipathic.3Triglycerides have a higher carbon content than phospholipids for storage purposes.4Phospholipids have hydrophilic regions to interact with cell cytoplasm unlike triglycerides.5Triglycerides are formed from glycerol and fatty acids but phospholipids are formed from glycerol and phosphoric acid only.A1, 3 and 5B1, 2 and 3

C1, 3 and 4D2, 3 and 42018 / H2 / DHS PRELIM / P1 Q59Which set of statements correctly describes haemoglobin?AFour polypeptide chains, each containing a prosthetic groupIron ions can associate with oxygen forming oxyhaemoglobinIn each chain, hydrophobic R groups of amino acids point towards the centre of the moleculeAt 50% saturation, two oxygen molecules are transported by the moleculeBPolypeptide chains interact to produce a globular chainEach chain contains a prosthetic group of amino acids surrounding an iron ionTwo identical alpha chains and two identical beta chainsEach chain can transport an oxygen moleculeCPolypeptide chains interact to produce an almost spherical moleculeAn iron ion is present within each haem groupQuaternary structure of two alpha chains and two beta chainsEach molecule can transport a total of four oxygen atomsDPolypeptide chains produce a loose helical shape, which curls to form a spherical moleculeIron ions in the molecule can bind reversibly with oxygenIn each chain, hydrophobic R groups of amino acids surround the iron ionEach molecule can transport a total of eight oxygen atoms

2018 / H2 / DHS PRELIM / P1 Q610 The flowchart below shows part of an enzyme-catalysed sequence which involves 4 compounds (W – Z) and 3 enzymes (E1 – E3). E1 The addition of another compound M results in no change in the concentration of compound W, an accumulation of compound X, and a near absence of both compound Y and compound Z.What does this information indicate about the mode of action of compound M, and which is a method by which the production of compound Z can be increased in the presence of compound M?Mode of action of compound MMethod to increase production of compound ZAIt inhibits E1.Increase concentration of compound X in the reaction mixture.BIt activates E1.Increase concentration of E2 in the reaction mixture.CIt inhibits E2.Increase concentration of compound Y in the reaction mixture.DIt inhibits E3.Increase concentration of compound Y in the reaction mixture.

2018 / H2 / EJC PRELIM / P1 Q111A lab technician has 5 tubes containing unknown compounds. However, he knows that each tube contains only either a carbohydrate or enzyme. To determine the identities of the compounds in the 5 tubes, the lab technician conducted various tests and he made the following observations.ISample in tube 2 is soluble in water. Sample in tube 3 was insoluble in water. IITube 5 tested positive with Biuret’s test.IIIContents of all 5 samples tested negative with Benedict’s test. IVHowever, after he mixed and incubated the contents of certain tubes together, a positive result was obtained for Benedict’s test. The mixtures were also subjected to paper chromatography, and the results were shown below. Which of the following correctly shows the contents of each tube?tube 1tube 2tube 3tube 4tube 5AamylasecellulosesucrosecellulasesucroseBcellulasesucrosecellulosesucraseamylaseCcellulosesucrosecellulosesucraseamylaseDsucrosecellulosesucraseamylasecellulase2018 / H2 / EJC PRELIM / P1 Q212The graph below shows the effect of increasing substrate concentrations on the activity of an allosteric enzyme under optimum conditions.

Which of the following statements is correct?AThere is low kinetic energy at X to overcome the activation energy, thus resulting in a low rate of reaction.BRate of reaction increases at a faster rate at Y as the allosteric activator outcompetes the allosteric inhibitor to bind to the allosteric site.CAt Z, enzyme molecules are in the active state and active sites are saturated.DSubstrate conc