Name: ________________________________ Deadline: 01/15/19’ TOPIC 8 PAST IB QUESTIONS TAKE HOME QUIZ FOR 12C 1. What process occurs during the light-independent reactions of photosynthesis? A. Oxygen is released into the atmosphere. B. Protons are pumped from the thylakoid space to the stroma. C. RuBP is carboxylated then regenerated in the Calvin cycle. D. Triose phosphate is converted to glycerate 3-phosphate. 2. Compare competitive and non-competitive enzyme inhibition. 3. The electron micrograph below shows an organelle in a eukaryotic cell. What is the area labelled X and what is the type of reaction occurring there? 4. Where is chlorophyll found in a plant cell? A. Thylakoid membranes B. Stroma C. Matrix D. Cristae 5. Where is ATP synthase located? 6. What occurs during the light-independent reactions of photosynthesis? A. ATP is produced. B. Ribose reacts with carbon dioxide to form glucose. C. Energy for the cycle is provided by the light-dependent reaction. D. Darkness stimulates the conversion of glucose to starch. 7. Which of the following is a role of ATP in photosynthesis? A. It provides the energy to make carbohydrate molecules. B. It splits water molecules to form oxygen and hydrogen. C. It breaks down pyruvate into carbon dioxide. D. It converts light energy into chemical energy. 8. Metabolic pathways can be controlled by end-product inhibition of the enzyme-catalysed reactions. KAS III is the initial enzyme of fatty acid production in plants and bacteria. The substrates for this reaction are acetyl CoA and malonyl-ACP. Three different strains of plant were generated, each with a different mutated KAS III gene: M1, M2 and M3. The enzyme activity of the normal (wild-type) and the three mutant strains was tested without and with the addition of the inhibitor, dodecanoyl-ACP. Dodecanoyl-ACP has a similar structure to malonyl-ACP. The graph shows the mean activity of the enzymes. a. State the activity of the wild-type enzyme without the inhibitor and with the inhibitor. Without inhibitor: With inhibitor: b. Distinguish between the enzyme activity without the inhibitor in the wild-type and the mutant strains. c. Explain why the activity of the enzyme from wild-type plants changes when the inhibitor is added. 9. Trypanosoma brucei is a parasite which causes sleeping sickness. The parasites rely exclusively on glycolysis for energy production. Peptides acting as inhibitors of an enzyme from the glycolytic pathway are being studied as possible drugs to kill the parasite. The glycolytic enzyme triose phosphate isomerase was incubated in the presence of various concentrations of three different peptides and the remaining activity was measured. As a control, the enzyme was incubated without inhibitor peptides. a. State the remaining activity of triose phosphate isomerase when 8 μmoldm−3 of peptide 1 is used. ..................% b. Compare the effect of increasing the concentration of peptide 2 and peptide 3 on the remaining activity. c. Identify, with a reason, which of the peptides is the most effective inhibitor of triose phosphate isomerase. d. Deduce, with reasons, whether the peptides act as competitive or non-competitive inhibitors of triose phosphate isomerase. 10. a. State the site of the light-independent reactions of photosynthesis. b. Explain the relationship between the structure of the chloroplast and its function. 11. A substrate undergoes a series of enzyme-catalysed reactions to form intermediate substances X, Y and then the final product. What would be the effect on the reaction of adding a competitive inhibitor to enzyme 2? A. The substrate would not react to form intermediate X. B. The concentration of intermediate X would increase. C. The activity of enzyme 3 would increase to compensate. D. No final product would be formed. 12. Where precisely in the cell do the reactions of the Krebs cycle take place? A. In the cytoplasm B. In the space between the inner and outer membrane of the mitochondria C. On the surface of cristae in the mitochondria D. In the fluid matrix of the mitochondria 13. In the mitochondrial electron transport chain, what is the last electron acceptor? A. CO2 B. H2O C. O2 D. NAD 14. The following graph shows energy changes with and without enzymes during a chemical reaction. Which letter represents the activation energy required to carry out this reaction without an enzyme catalyst? 15. The diagram represents components of the cristae in mitochondria. Which arrow indicates how protons (H+) move to generate ATP directly? 16. a. State the location of high proton concentration caused by electron transport in the mitochondrion. b. Outline the role of oxygen in cellular respiration. c. Explain how any two structural features of the mitochondrion are related to its function. 17. The Haberlea rhodopensis plant is capable of tolerating extreme dryness. Chlorophyll levels and CO2 assimilation were evaluated during dehydration and rehydration using plants grown in shade and sunlight. Graph A shows the changes in chlorophyll content with increasing dehydration and during rehydration. Graph B shows the changes in CO2 assimilation with increasing dehydration and during rehydration. a. State the level of chlorophyll at 50 % water content for plants growing in sunlight, giving the units. b. Outline the effect of sunlight and shade on CO2 assimilation during dehydration. c. Compare the effect of rehydration on chlorophyll levels in plants grown in shade and sunlight. d. Using the data, deduce, with a reason, two stages of photosynthesis that may be limited during dehydration in a plant. 18. What is chemiosmosis? A. Coupling of ATP synthesis to the electron transport and proton movement B. Phosphorylation of glucose in the mitochondrial matrix C. H+ ions moving down a concentration gradient into the mitochondrial matrix D. Activation of ATPase in order to synthesize ATP 19. The graph shows an example of an enzyme-catalysed reaction. What does the curve labelled X represent? A. No inhibition B. Competitive inhibition C. Non-competitive inhibition D. Reversible inhibition 20. The diagram represents the Krebs cycle. What processes are occurring at I and II?