AQA A-Level Biology Paper 2 Predicted Paper 2023 with marking scheme attached

AQA A-Level Biology Paper 2 Predicted Paper 2023 Name …………………………………………………………………… Date ………………… 2 hours allowed. You may use a scientific calculator and a ruler with millimetre measurements. Grade boundaries These are VERY rough guesses! Getting a B on this paper does not guarantee you the same mark in the exam. • A* 65% • A 55% • B 45% • C 40% • D 35% • E 30% 01 The image below shows a transmission electron micrograph of a longitudinal section of skeletal muscle viewed at x40 000 magnification. a) Name structures T, U and V. [3 marks] T: U: V: b) What is the name of the structure between points V and W? [1 mark] c) Explain what causes the banding pattern seen. [2 marks] d) Glycogen granules can be seen labelled in the image. In which type of muscle fibre would you expect to find high concentrations of glycogen granules? Explain your answer. [2 marks] e) During a contraction, muscle fibres shorten on average by around 28%. Estimate the distance between points V and W in µm if this muscle was contracted. [3 marks] f) Some toxins and venoms produced by predators prevent muscle contraction, paralysing their prey. The molecular structure of a kind of snake venom is very similar to the molecular structure of acetylcholine. Explain how this venom could prevent muscle contraction. [2 marks] 02 Farmers often use inorganic fertilisers on their fields to increase the amount of nutrients available to growing crops. These fertilisers contain a mixture of nitrates and phosphates. a) Describe the molecular processes that require phosphates in a growing plant. [4 marks] b) Explain why it is important for a farmer to try and reduce the possibility of these fertilisers running off the fields. [2 marks] Arbuscular Mycorrhizal Fungi (AMF) grow on and into the roots of plants forming a natural association. They can support plants in low nutrient soils to obtain more inorganic ions including phosphate. c) Suggest one way in which the AMF may benefit from the plants they grow on in this relationship. [1 mark] d) Some scientists wanted to investigate the benefits of AMF on increased biomass of plants in low nutrient soils. They took samples of soil from low nutrient fields and soil from a fertilised (high nutrient) field. They filled pots with these soils and grew some lettuce with two different species of AMF. In each of the experiments they also added a control group soil. Their results after leaving the plants to grow for 8 weeks can be seen in the graph below. i. Suggest what the scientists would have done to create the control pots? [1 mark] ii. Explain why the shoots were dried before they were weighed. [1 mark] iii. Explain why shoot biomass increase can be used to demonstrate net primary productivity. [2 marks] iv. Using the graph, evaluate the effect of adding the AMF species on plant growth in the different soils. [4 marks] 03 The diagram below shows a pressure receptor from the skin attached to its sensory neurone. a) What is the name of this type of receptor? [1 mark] Microelectrodes were used to measure the membrane potential of the axon at points A and B. The time between depolarisations of the axon at the two points was also recorded. The results are shown in the table below: Type of pressure applied to skin Membrane potential measured (mV) Time between impulses (ms) Point A Point B None -75 -75 0 Light -52 -75 0 Medium +30 +38 0.8 Heavy +38 +38 0.8 b) Explain how the receptor produces the changes in membrane potential at point A when pressure is applied. [3 marks] c) Explain why the membrane potential does not increase at point B between medium and heavy despite more pressure being applied. [2 marks] d) The distance between points A and B is 8cm. Use the information from the table to calculate the speed of the impulse along the sensory neurone in meters per second. Show your working. [2 marks] e) What would you expect to happen to the speed of the impulse if the diameter of the axon of the sensory neurone was increased? Explain your answer. [2 marks] 04 a) Define phenotype [2 marks] In horses coat colour is controlled by two different genes B and C. The two genes are not linked but the effects of the alleles interact to produce different coat colours. The table gives some examples of genotypes and which coat colour they produce: Genotype Phenotype BbCc Brown bbCc Tan Bbcc White/No pigment bbcc White/No pigment b) What colour would you expect the coats of horses with the following genotypes to have? [2 marks] i. BBCc _ ii. bbCC _ c) Genes B and C are not linked. Complete a genetic diagram to show all the possible genotypes and the ratio of phenotypes expected in the offspring of the following cross: [3 marks] Genotypes of parents BbCc x BbCc Genotypes of offspring Phenotypes of offspring Ratio of phenotypes d) Explain the gene interaction that has produced the phenotypic ratio shown by the cross. [2 marks] 05 A student measured the rate of photosynthesis in an aquatic plant when exposed to different wavelengths of light. The results are shown in the graph. a) Give one dependent variable the student could have measured in order to determine the rate of photosynthesis in the aquatic plant. [1 mark] b) Use the graph to identify which wavelengths of light would have been from green light. Give a reason for your answer. [2 marks] Wavelength range: nm Reason The student then extracted chloroplasts from the aquatic plant and added a buffer to form a chloroplast suspension. They added a dye called DCPIP. DCPIP is blue when oxidised and colourless when reduced. In order to investigate the light dependent reactions of photosynthesis, the following experiment was conducted. The student set up the test tubes as follows:  Tube A – buffer with no chloroplasts and DCPIP under a lamp  Tube B – chloroplast suspension and DCPIP under a lamp  Tube C – chloroplast suspension and DCPIP wrapped in black paper The colour of the mixture in the tube was recorded after 30 minutes. The results are shown in the table below. Colour of solution in tube after 30 minutes Tube A Blue Tube B Green Tube C Blue c) Explain why the buffer used to make the chloroplast suspension was isotonic. [2 marks] d) Use your knowledge of the light dependent reactions to explain the results in Tube B. [2 marks] e) DCMU is used as a weed killer as it inhibits electron transfer. The student set up another tube in the same way as Tube B but added some DCMU. What would you expect the colour of solution to be after 30 minutes? Explain your answer. [2 marks] f) Explain how DCMU works to prevent the growth of weeds. [2 marks] Explain why an increase in blood pressure causes heart rate to decrease. [6 marks]