2025 NYJC H2 Chem Biomolecules and Enzymes Remedial QP 1

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 1 Remedial Practice: (Topic A & C: Biomolecules & Enzymes) Name: Class: Date: 1 Fig. 1.1 shows five different biological molecules. Fig. 1.1 Fig. 1.1

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 2 (a) Complete Table 1.1 by indicating which molecule matches each statement. You may use each letter (H to M) once, more than once, or not at all. You should write only one letter in each box. Table 1.1 statement letter contains peptide bonds part of the molecule forms the hydrophobic part of cell membranes contains 1,4 and 1,6 glycosidic bonds forms the primary structure of a protein forms a helical structure the sub-unit molecule is β-glucose [3] (b) Fig. 1.2 is a diagram of part of an α-helix of a polypeptide chain commonly found in many types of protein. (i) Name the repeating monomer of a polypeptide chain. [1] Fig. 1.2

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 3 (ii) Explain what would happen to the α- helix if the polypeptide chain was heated to a temperature above 60 °C. [3] The primary structure of a collagen polypeptide has a repeating pattern of three amino acids. Fig. 1.3 shows the two forms of this pattern. Fig. 1.3 (c) Glycine makes up approximately 30% of the total amino acid composition of collagen. Fig 1.4 shows the molecular structure of glycine. Fig. 1.4 (i) On Fig. 1.4, draw a box around the R-group of glycine. [1]

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 4 (ii) Explain how glycine plays an essential role in the structure of collagen. [2] Collagen and cellulose are structurally similar and both provide structural functions. Collagen is a key biomolecule found in the skin, bone, connective tissue and tendons in animals while cellulose is found in plant cell walls. (d) (i) Describe how the similarities in their structures that allow them to perform structural and supportive functions. [3] (ii) Describe how, other than the chemical bonds and the names of the monomers present, the structure of a cellulose differs from that of collagen. [2] [Total: 15]

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 5 2 Monosaccharides may be used to build a wide variety of biological structures. Fig. 2.1 shows two simplified β-glucose molecules. Fig. 2.1 (a) (i) Draw a diagram in the space below to show how these molecules can bond together. [2] (ii) State the name of the bond you have drawn. [1]

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 6 (b) State one similarity and one difference between the structure of ribose and the structure of β-glucose. similarity difference [2] (c) Another form of glucose is α-glucose. (i) Describe the advantages to a plant of condensing α-glucose molecules into starch. [4] (ii) Suggest why mammals store α-glucose as glycogen rather than as starch. [1] [Total: 10]

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 7 3 Starch phosphorylase is an enzyme found in plant cells. In potato tuber cells, the enzyme takes part in the breakdown of starch when the tube begins to grow. Starch phosphorylase can be inhibited by competitive inhibitors like cyclodextrin. Fig. 3.1 illustrates the model of enzyme action of starch phosphorylase. Fig. 3.1 (a) Using Fig. 3.1, (i) describe how the enzymes take part in chemical reactions. [3]

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 8 (ii) explain competitive inhibition. [3] A student investigated the effect of pH on this reaction using two buffer solutions. The student prepared three test-tubes, A to C, as shown in Table 3.1. The enzyme extract was made from potato tissue. A solution of potassium dihydrogen phosphate was added to some tubes as a source of phosphate ions. The test-tubes were left for ten minutes in a water bath at 30 oC and then samples were tested with iodine solution. Table 3.1 (b) Suggest why the student boiled some of the extract in this investigation. [2] test- tube contents results with iodine solution after ten minutes volume of starch solution/cm 3 volume of glucose-1- phosphate solution/cm 3 volume of potassium dihydrogen phosphate solution/cm 3 pH of buffer solution enzyme extract A 2 0 0.5 6.5 unboiled negative B 2 0 0.5 2.0 unboiled positive C 2 0 0.5 6.5 boiled positive

NANYANG JUNIOR COLLEGE H2 Biology Biomolecules & Enzymes J2 9 (c) Explain the results of Tube B shown in Table 3.1. [3] [Total: 11] 4 Explain the mode of action of an enzyme in relation to its protein structure. [7]