AS-Level Biology Paper 1 Predicted Paper 2023 attached with marking scheme

AS-Level Biology Paper 1 Predicted Paper 2023 attached with marking scheme Name …………………………………………………………………… Date ………………… 1 hour 30 minutes 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 60% • B 50% • C 40% • D 35% • E 30% The diagram below shows a molecule of glucose. a) What disaccharide would two molecules of this monosaccharide form when joined together? [1 mark] b) Name the bond that forms between two monosaccharides? [1 mark] c) Describe how this bond is formed. [2 marks] d) These monosaccharides can join to make the polysaccharide amylopectin. Name and explain one feature that makes amylopectin a good storage molecule. [2 marks] The diagram below shows a micrograph of an E. coli bacterium taken using an electron microscope. The length of the bacterium is 8µm. a) Calculate the magnification of the microscope used to take the image. [2 marks] Magnification = b) What type of electron microscope was used to obtain the image shown in the diagram above? Give one piece of evidence to support your answer. [2 marks] Type of microscope: Evidence: c) In order to view the cells under the microscope a student had to dilute the bacterial culture. Describe how the student could have used a dilution series to obtain a 1 in 1000 dilution of the original bacterial culture. [3 marks] d) The student spread the E. coli bacterial culture on an agar plate in order to determine the effect of different antibiotics used to treat patients with E. coli infections. Her plate can be seen in the diagram below. Describe and explain two aseptic techniques the student would have used when preparing the plate in the image. [2 marks] The diagram shows part of the gas exchange system of an insect. A a) Identify the structures labelled A and B in the diagram above. [2 marks] A: B: b) Why is it necessary for insects to be able to close the structures labelled A? [1 mark] c) Explain how the structures in this system in insects are adapted for efficient gas exchange. [3 marks] The human body has an in-built protection system that provides resistance to diseases and pathogens. It is referred to as the body’s immune system. The immunity provided by the immune system can either be active, or passive. Including examples, explain the differences between active immunity and passive immunity. [5 marks] Catalase is an enzyme found in liver cells which breaks down hydrogen peroxide into oxygen and water. Hydrogen peroxide is a metabolic product produced in significant quantities in liver cells. It needs to be removed in order to prevent serious damage to the liver cells. Catalase has a very high turnover number. A single molecule of catalase can catalyse the breakdown of approximately 6 million H2O2 molecules every minute. Two students wanted to investigate the effect of temperature on the rate of reaction of the enzyme catalase taken from pieces of liver tissue. Catalase enzymes are found in small vesicles called peroxisomes in liver cells. a) In order to carry out their experiment the students had to chop and then blend the liver tissue to isolate the enzyme. Explain why. [2 marks] The experiment was performed at a range of different temperatures and rate of reaction was obtained. The graph below shows their results. b) Identify two variables that would need to be controlled in this laboratory investigation. [1 mark] c) How could you control the variables that you identified in (b.) in the laboratory investigation? [2 marks] d) Using your knowledge explain the change in the graph seen after 40⁰C. [3 marks] e) Using catalase as an example, explain enzyme specificity. [3 marks] f) A teacher asked the two students to state the optimum temperature for this enzyme. Student A gave the answer ‘40⁰C’ but student B gave the answer ‘somewhere between 30⁰C and 50⁰C’. The teacher said that student B had given the better answer. Explain why student B’s answer was better. [2 marks] 06 A group of cells is referred to as a tissue. In plants, groups of different cells form different plant tissues. Xylem and phloem are two such tissues in plants. a) What is the function of xylem tissue? [1 mark] b) Describe and explain three adaptations of xylem cells that allow them to carry out their function. [3 marks] c) The rate of flow of water in the xylem of a tree trunk was measured along with the average number of stomata open during a 24-hour period. The results are shown in the graph below: