2024 TJC H2 Bio P2 MS

1 JC2 PRELIMS 2024 H2 PAPER 2 1 (a) Fig. 1.1 is a diagram of a section through a mitochondrion. Fig. 1.1 (i) On Fig 1.1 , use label lines and letters to label the positions where the following reactions take place: [3] X - Link reaction Y - Krebs cycle Z - Oxidative phosphorylation [occurs in inner mitochondrial membrane] 1 mark each (ii) The four arrows, A, B, C and D, show the movement of molecules and ions. Use the letters to identify all the arrows (one or more) that show: [2] Active transport of protons D Diffusion of carbon dioxide C and D (b) Compare the process of oxidative phosphorylation with photophosphorylation. [2] SIMILARITIES (Any 1): S1. Electrons passed down electron carriers of decreasing energ y level in electron transport chain in both processes. S2. Pumping of H+ across membrane to create steep proton gradient in both processes. S3. D i f f u s i o n of H+ via hydrophilic channel of ATP synthase (stalked particle) to synthesize ATP in both processes. S4. Use of energy released from electrons transported down energy level i n electron transport chain to pump H+ to create proton gradient in both processes. DIFFERENCES (Any 1): X and Y Z [occurs in matrix of mitochondrion] O2 and pyruvate (from glycolysis) enter the mitochondrion CO2 leaves the mitochondrion CO2 leaves the mitochondrion & H+ pumped from matrix to IMS H+ diffuses from IMS into matrix

2 Feature of comparison Photophosphorylation Oxidative phosphorylation D1. Location  Thylakoid of chloroplasts  Inner mitochondrial membrane D2. Source of electrons  [Non-cyclic] Water  [ C y c l i c ] PS I  NADH  FADH2 D3. Final electron acceptor  [Non-cyclic] NADP+  [ C y c l i c ] PS I  O2 D4. Products formed  NADPH  H2O D5. Requirement of light energy  Yes for photolysis of water  No D6. Source of energy  Light  Oxidation of glucose D7. Direction of H+ pumped to generate steep proton gradient  Pumped from stroma to thylakoid space  Pumped from matrix to intermembrane space D8. Direction of H+ diffusion to synthesize ATP  Diffusion from thylakoid space to stroma  Diffusion from intermembrane space to matrix (c) Apart from channel proteins that allow transport of ions , plant and animals cells also have channel proteins such as aquaporins which permits the movement of water across membranes. Explain why aquaporins are necessary. [3] 1. Cell surface membrane is made up of phospholipid bilayer 2. Has a hydrophobic boundary/core due to presence of non-polar fatty acid tails 3. Water molecules are small and polar 4. Onl