A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+, Exams of Nursing

Download A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ and more Exams Nursing in PDF only on Docsity! A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ RP01 - Rate of an Enzyme Controlled Reaction - correct answers What are the factors that affect enzyme activity (4)? - correct answers 1. Enzyme concentration 2. Substrate concentration 3. Temperature 4. pH How is a control set up in a practical measuring enzyme activity? - correct answers Replace the enzyme solution with distilled water or boiled enzyme solution. How can the results of the practical measuring enzyme activity be used to find the initial rate of reaction? - correct answers Plot your results on a graph of 'rate of reaction' against 'time'. Draw a tangent at time = 0 to find the initial rate. Outline the practical procedure used to measure the effect of temperature on enzyme activity, using trypsin and milk. - correct answers Immerse equal volumes of trypsin and milk, stored in different test tubes, in a water-bath for 5 minutes for the temperature to equilibrate. Mix together and immediately start timing, record the time taken for the milk to be completely hydrolysed (become colourless/ same as the control standard set up). Test at least 5 temperatures, with at least 3 repeats at each temperature. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ How is the rate of reaction calculated from time? - correct answers Rate of reaction = 1/time What is the effect of temperature on enzyme activity? - correct answers As temperature increases, kinetic energy increases so more ES complexes form. The rate of reaction increases up to the optimum temperature. Beyond that, bonds in the enzyme tertiary structure break, which changes the shape of the active site. The substrate and enzyme are no longer complementary, so rate of reaction decreases. What is the risk and level of risk associated with handling enzymes? - correct answers Students may have allergic reactions to enzymes, so avoid contact with skin and eyes, wear eye protection. Low risk. RP02 Calculating Mitotic Index using Plant Cells - correct answers Where in plants can cells undergoing mitosis be found? - correct answers Meristem tissue at shoot and root tips. What is the mitotic index? - correct answers The ratio of cells undergoing mitosis to the total number of cells in a sample. Outline the procedure to prepare a root tip slide. - correct answers Warm 1M HCl to 60°C in a water bath. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ Add 5 cm3 to 5 different test tubes. Cut a potato into equal sized chips and weigh. Place a chip in each test tube and leave for 20 minutes. Take out, dab the excess water and weigh them again. (using a 2dp balance) Calculate the percentage change in mass. Why is the percentage change used rather than the actual change in mass? - correct answers Potato chips may not all have same starting mass. Percentage change allows comparison. What is indicated by the x-intercept of the calibration curve? - correct answers The concentration that is isotonic to the solution tested. Explain the change in mass in the potato chips. - correct answers The potato chips with concentration lower than the sucrose solution (higher water potential) lose mass as there is a net movement of water out of the cells. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ The potato chips with concentration higher than the sucrose solution (lower water potential) gain mass as there is a net movement of water into the cells. Why are the potato chips dabbed dry after removing from the sucrose solution? - correct answers To remove any excess water clinging to its surface that may add mass to the potato. What are the controlled variables of this practical? - correct answers Volume of sucrose solution Size of potato chips Length of time left in solution Dab each potato disc with paper towels RP04 - Investigating Cell Membrane Permeability - correct answers State 2 factors that affect the permeability of cell membranes. - correct answers Temperature Concentration of solvents (ethanol) How is beetroot used to measure the permeability of cell membranes? - correct answers The higher the permeability, the more red pigment that leaks out into the surrounding solution within a given time. A colorimeter can be used to determine the absorbance, hence concentration of pigment. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ Outline the procedure to investigate the effect of temperature on permeability of cell membrane. - correct answers Cut beetroot into 6 identical cubes with a scalpel. Place each cube in a different test tube with equal volumes of distilled water. Place each test tube into water baths ranging from 30-80° C. Leave for 20 minutes. Filter each solution out into a cuvette and measure the absorbance using a colorimeter. What are the safety hazards involved in testing the effect of ethanol concentration on membrane permeability? - correct answers Ethanol is an irritant and is flammable, keep away from naked flames, wear eye protection. Keep sharp scalpel away from fingers. Handle hot liquid with care. What is the effect of temperature on membrane permeability? - correct answers Increasing temperature results in increase membrane permeability. What is the effect of ethanol concentration on membrane permeability? - correct answers Increasing ethanol A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ Why should the lid not be completely taped to the petri dish? - correct answers To allow oxygen to enter the petri dish, preventing the growth of harmful anaerobic bacteria. Describe the graph that can be plotted from the results of this practical. - correct answers A bar chart of zone of inhibition against antibiotic. RP07- Chromatography of photosynthetic pigments - correct answers What is the purpose of chromatography? - correct answers To separate different components in a sample. State the factors affecting the rate of migration of different pigments. - correct answers Solubility Mass Affinity to the paper What is the formula of the RF value? - correct answers Distance moved by pigment / Distance moved by solvent What is the purpose of finding the RF value of a pigment? - correct answers Experimental RF value can be compared to a standard value in a database to identify the pigment. The standard value should be measured A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ using the same paper and solvent. Outline the procedure of using chromatography to separate photosynthetic pigments. - correct answers Draw a horizontal pencil line 1cm above the bottom of the filter paper. Add some acetone and use the mortar and pestle to grind up the leaf sample and release the pigments. Use a capillary tube to transfer the pigment onto the pencil line. Suspend the paper in the solvent so that the level of the liquid does not lie above the pencil line and leave the paper until the solvent has run up the paper to near the top. Remove the paper from the solvent and draw a pencil line marking where the solvent moved up to. Calculate the Rf value for each spot. State the hazards and precautions in this practical. - correct answers Solvents are irritant and flammable. Keep away from naked flames, wear eye protection and avoid contact with skin. Leaf extract may be a biohazard. Wash hands after use. RP08 - Dehydrogenase Activity in Chloroplasts - correct answers A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ What is the function of dehydrogenase in chloroplasts? - correct answers It catalyses the acceptance of electrons by NADP in the light dependent reactions. What is the purpose of DCPIP? - correct answers It is a redox indicator dye and acts as an alternate electron acceptor instead of NADP. It turns from blue to colourless when reduced. Why is the plant extract chilled in an ice-water bath? - correct answers To lower the activity of enzymes to prevent them from breaking down the chloroplasts. How is the control set up? - correct answers Fill a cuvette with chloroplast extract and distilled water. How is light intensity controlled? - correct answers Adjust the distance of the lamp from the set up. Perform the practical in a dark room so that the only light source is the lamp. What is the function of the muslin cloth? - correct answers To filter out any debris in the ground leaf mixture but allowing chloroplasts to pass through. Why are the stalks of leaves removed before grinding? - correct answers The stalks do not contain many chloroplasts. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ What is the effect of temperature on the rate of respiration? - correct answers As temperature increases, the rate of respiration increases to an optimum. This is because the rate of enzyme activity increases. Beyond the optimum, enzyme activity decreases as enzymes denature with high temperature. RP10 - Investigating Simple Animal Responses - correct answers How can a choice chamber be used to measure the favourable environment of a small organism? - correct answers By setting up chambers in different quadrants with different environmental conditions: dark + dry, dark + damp, light + dry, light + damp Organisms will move to the quadrant they find favourable What factors must be controlled when repeating the experiment? - correct answers Number of animals Environmental conditions Time allowed for animals to choose Which statistical test is used to analyse the results of this practical and why? - correct answers Chi squared test. It compares the expected and observed values, and tests if there is a significant difference. A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ What is the conclusion drawn if the calculated value is greater than the critical value? - correct answers Null hypothesis is rejected. Less than 5% probability that the difference is due to chance alone. There is a statistically significant difference between the expected and observed values. What do animals do when they are in unfavourable environments? - correct answers They move faster and change direction more frequently to increase their chances of survival. State the hazard and precaution involved in this practical. - correct answers The live organisms used are a biohazard. Wash hands after handling. RP11 - Measuring the Concentration of Glucose using a Calibration Curve - correct answers How can Benedict's solution be used to measure the concentration of glucose in a solution? - correct answers Use a colorimeter to measure the absorbance of a series of solutions of known concentrations to create a calibration curve. Compare the absorbance of an unknown sample to the calibration curve. What is a serial dilution? - correct answers A dilution where successive concentrations increase/decrease in a logarithmic fashion A level Biology paper 3 exam questions and answers latest update 2023/2024 graded A+ Outline the procedure of this practical. - correct answers Make a serial dilution of glucose, ranging from 0 to 10 mmol dm-3 . Place 2 cm3 of each of the unknown samples in separate boiling tubes. Add 2 cm3 of Benedict's solution to all boiling tubes. Place boiling tubes in a water bath at 90°C for four minutes. Zero the colorimeter using a cuvette with distilled water and set to red filter. Place known samples into cuvette and measure the absorbance of each using the colorimeter. Make a calibration curve. Measure the absorbance of the unknown samples using the colorimeter. Use the calibration curve to determine glucose concentrations. What are the axes in a calibration curve? - correct answers Absorbance against glucose concentration. What would a high glucose concentration in urine suggest? - correct answers It may suggest diabetes. Lack of insulin leads