2024 Dec Revision H2 Ans ASRJC J1 H2 BIO

Anderson Serangoon Junior College Biology Department 1 JC1 December Revision Question 2024 JC1 DECEMBER REVISION–ANSWERS NAME: ………………………………………………… Class: ………………………… Topic: CELLULAR STRUCTURES AND FUNCTION Question 1 [6 marks] TJC Prelims 2009 (a) With reference to Fig. 1.1, suggest the principal function of the pancreatic acinar cell. Give two reasons to explain your answer. [3] Function • secretion of pancreatic / digestive enzymes or secretion of hormones Reasons • presence of large amount of R ER, which is the site where pancreatic enzymes are synthesized • presence of SER, which is the site where steroid hormones / lipids are synthesized • presence of large number of secretory vesicles for release of pancrea tic enzymes/ hormones outside the cell • presence of mitochondria which synthesizes ATP for o Activation of amino acids OR o Formation of peptide bonds (at ribosomes) OR o Transport / Movement of vesicles towards cell surface membrane for r elease of pancreatic enzymes/ hormones (b) (i) Describe two ways in which A is similar to B. [2] • Both are bound by a single membrane / single membrane-bound structures. • Both consist of membranous sacs called cisternae, in which newly synthesized proteins undergo processing. • Both give rise to membrane-bound vesicles which are involved in transport of newly synthesized proteins within the cell. (ii) The products of B are usually in the inactive form. Suggest the significance of this. [1] • to prevent the enzymes (of lysosomes) from digesting proteins / contents within the cells in which they are synthesized

Anderson Serangoon Junior College Biology Department 2 JC1 December Revision Question Topic: BIOMOLECULES AND CELL MEMBRANE Question 2 [11 marks] (a) Draw the resulting maltose molecule arising from a dehydration reaction. [1] (b) Label the resulting bond. [1] • Alpha (1→4) glycosidic bonds Starch, a storage molecule in plants, is a polymer made of glucose molecules joined together. It consists of two components. (c) Name these two components. [2] • amylose • amylopectin (d) (i) Give one similarity between these two components. [1] • contain α-glucose as monomers • coiled into a helix • no cross-linking (ii) Give two differences between these two components. [2] • The amylose component is unbranched whilst the amylopectin component is branched. • The glucose residues in the amylose component are linked by (1→4) glycosidic bonds, whilst the glucose residues in the amylopectin component are linked by both (1→4) glycosidic bonds and (1→6) glycosidic bonds ( at the branchpoints) (f) The following figure shows a section of a cell surface membrane. (i) Explain why membranes are described as fluid mosaic in structure. [2] ‘Fluid’ (any 1) • phospholipids and proteins free to move laterally within the membrane • phospholipids able to move transversely / flip flop ‘Mosaic’ • Different proteins randomly scattered embedded/ ref. to position

Anderson Serangoon Junior College Biology Department 3 JC1 December Revision Question (ii) Some molecules are able to pass through the plasma membrane without the facilitation of transport proteins. Describe the unique properties of these molecules. [1] • small / non-polar / hydrophobic (iii) Outline two other roles of membrane proteins apart from their role in transport. [2] • Enzymatic activity: Protein has its active site exposed to substances in the adjacent solution. → Enables the cell membrane to be involved in certain metabolic pathway • Signal transduction: Protein function as receptors for extracellular signaling molecules → allow cells to sense changes in the external environment and respond to them • Glycoproteins serve as cell identity markers → Enable cells to recognize other cells • Membrane proteins of adjacent cells may be attached → Enables cell-to-cell adhesion • A protein built into the membrane may be an enzymes with is active site exposed to substances in the adjacent solution. • Membrane proteins may be bonded to components of the cytoskeleton→ maintains cell shape Topic: ENZYMES Question 3 [ 7 marks] JJC Prelims 2009 (a) Suggest how the protein may be held in the active site of a papain while the reaction occurs. [2] • Protein substrate has shape complementary to the shape of the active site of the enzyme • enzyme interacts with the substrate via hydrophobic interactions, h ydrogen bonds and ionic bonds → temporary enzyme-substrate complex (b) Use your knowledge of enzymes to explain: (i) Why the rate at which protein is digested increases as the meat warms up in the early stages of cooking. [2] • In early stages of cooking, heating increases the kinetic energy of both papain and protein molecules in the muscle • rate of successful collisions / number of collisions per unit time between papain and protein molecules increase;→ increase rate of formation enzyme-substrate complexes/ number of E-S complexes per unit time ; (ii) Why protein digestion stops once the meat has been heated to 90oC. [3] • At 90oC, large amount of heat present resulting in denaturation of papain; • bonds ( give 2 examples: hydrogen bonds, hydrophobic interactions, ionic bonds) maintaining the 3D conformation of enzyme are broken • causing loss of active site / change in shape of active site → shape of active site no longer complementary to substrate

Anderson Serangoon Junior College Biology Department 4 JC1 December Revision Question Question 4 [ 6 marks] (i) Using the information in Fig 4.1, describe and explain the results obtained for test tubes 1 and 4. [3] • Tube 1– from 0min to 50min, percentage transmission increases from 20% to 70% and then levels off/ remains constant at 70% for the next 10mins • (increases) as more substrate had been converted/ [substrate] decreases. Levels off as all substrate has been converted • Tube 4 – remains cons tant/ remains at 20% (Reject – no transmission ) as pectinase denatured (ii) Explain why test-tube 2 was included in the experiment. [2] Control; To show that enzyme/ pectinase is the only factor responsible for cloudiness clearing/ increase in transmission (iii) Sketch on the graph the results you would expect for test-tube 3. [1] Horizontal line somewhere between 70 and 100% transmission Topic: CELL AND NUCLEAR DIVISION Question 5 [10 marks] (a)(i) Identify stages A to D. [2] A Metaphase I B Anaphase I C Telophase I D Anaphase II (ii) State the type of nuclear division shown in Fig. 5.1 [1] Meiosis (iii) Explain your answer to part (ii). [1] • 2 nuclear divisions resulting in 4 nuclei/cells formed from 1 cell (b) The graph below shows the relative amounts of DNA per cell during two successive cell divisions in a plant. (i) Describe the events occurring at X. [3] • cytokinesis occurred where amount of DNA in the cell dropped from 4.8 units to 2.4 units and then becomes a constant • DNA replication occurred: Amount of DNA then doubled from 2.4 units to 4.8 units

Anderson Serangoon Junior College Biology Department 5 JC1 December Revision Question c) Draw the behaviour of the chromosomes undergoing anaphase II during nuclear division in the cell given below where (2n = 6). [3] • Number of replicated chromosomes = 3 • Separation of sister chromatids • At least 1 pair of sister chromatids must be non-identical Topic: DNA REPLICATION Question 6 [12 marks] ACJC Prelims 2010 (a) Describe the normal function of nuclear pores. [2] • regulates the movement of substances into and out of the n