RI Nov 15 H2P2 ans

Raffles Institution Nov 2015 (H2 Biology) Paper 2 (for 9744 syllabus) 2017 Nov 2015 H2 Bio Paper 2 N15P2Q1 (a) Identify the structures A and B, as shown in Fig.1.1. [6] For each structure, state two features that can be seen in Fig.1.1. structure A: mitochondrion (R: mitochondria) feature 1: double membrane feature 2: highly folded inner membrane/cristae structure B: rough endoplasmic reticulum feature 1: flattened sacs called cisternae studded with ribosomes feature 2: continuous with outer membrane of nuclear envelope (b) Describe two functions of the Golgi body.[2] 1. To glycosylate proteins and lipids to form glycoproteins and glycolipids respectively; 2. To modify existing glycoproteins and glycolipids by modifying/cleaving the existing sugar chains; 3. To sort and package proteins into different vesicles and target the proteins to different parts of the cell or for secretion; 4. To form lysosomes; 5. To synthesise polysaccharides such as pectin which is transported in vesicles to the cell membrane; (c) Suggest two advantages to eukaryotic cells of having membrane bound organelles.[2] Membranes allows for compartmentalisation which allow 1. unique environments to be formed for highly specialised activities (e.g. acidic environment in lysosomes for hydrolytic enzymes to work); 2. spatial separation of biochemical processes & thus their sequential operation within a cell (e.g. protein modification in RER and further protein modification, sorting and packaging in the GA) ; 3. accumulation of ions to high concentrations (e.g.accumulation of a high concentration of H+ in the intermembrane space of the mitochondria enable a proton gradient to be established for chemiosmosis); 4. Membranes act as a surface for chemical reactions to occur in a sequential manner membranes may have functionally -related proteins grouped together so that sequential biochemical processes can occur (e.g. the thylakoid membranes of the chloroplast have electron carriers & ATP synthetase for chemiosmosis to occur); 5. Membranes increase surface area for chemical reactions (e.g. inner mitochondrial membrane is highly folded to hold more electron transport chains and ATP synthetase); (d) Explain the role of glycogen in animal cells.[2] 1. Glycogen is an large energy store found in the liver and muscles; 2. which can be hydrolysed to many glucose molecules that can be used as a respiratory substrate which oxidized during respiration to produce ATP. [Total :12]

Raffles Institution Nov 2015 (H2 Biology) Paper 2 (for 9744 syllabus) 2017 N15P2Q2 (a) Describe how replication of the lagging strand template occurs. [2]