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

AQA A-Level Biology Paper 1 Predicted Paper 2023 attached with markingscheme 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 To look for the presence of starch in potatoes, a student decided to observe potato cells under a microscope. The image below shows starch grains present in potato cells viewed at a magnification of x400. a) Describe how the student could have prepared the sample to view under the microscope. [2 marks] b) Describe how the student identified that these grains contained starch. [2 marks] c) Calculate the actual length in µm of the starch grain between points A and B. [2 marks] Actual length = d) Plants store excess glucose as starch in their cells. Glucose can also be used to make cellulose to make cell walls. Explain how the structure of cellulose make it adapted for its function. [3 marks] a) Explain how water assists in metabolic reactions inside cells. [2 marks] b) The image below shows a freshwater pond. State and explain three properties of water that help organisms that live in the pond to survive. [3 marks] Sugars made in the leaves of plants must be transported to other tissues. One theory states that a pressure gradient is created from the leaves to the roots and that sugars are transported in the phloem under high pressure down the pressure gradient. a) Describe how high pressure in the phloem of leaves is created. [3 marks] Experiments have been carried out to find evidence which supports this hypothesis. A scientist wanted to observe the effect of ringing on the movement of substances in the phloem of apple trees. An experiment was devised and 10 specimen apple trees were picked by the scientist. She took 3 branches of equal diameter from below the leaves of each of the 10 trees and treated them under the following conditions: She then took tissue samples from branch areas below each treated section after 10 days. The analysis of the tissue samples is shown in the table below: Treatment A Treatment B Treatment C Sucrose Concentration (mg/cm3) 118.2 5.32 2.79 Amino Acid Concentration (mg/cm3) 5.3 0.04 0.19 Water content % 91 94 89 b) Explain how the scientist used control treatment A. [2 marks] c) The scientist observed swelling in the bark above the removed ring in treatment B. Explain this observation. [2 marks] d) Describe how the scientist could have calculated the water content of the tissue samples. [3 marks] e) The scientist concluded that both treatment B and C provide evidence for the mass flow hypothesis. Evaluate whether the information from this investigation supports this hypothesis. [6 marks] f) Some fruit growers use similar techniques of damaging bark to promote fruit growth in trees in their orchards. Explain why. [2 marks] 04 As a source of amino acids, proteins are an important part of the mammalian diet. Humans are also mammals and therefore consume and digest proteins. a) Describe how proteins are digested in the small intestine of humans. [4 marks] In ruminants like cows and sheep, protein is not only digested in the small intestine. Their digestive systems include a specialised chambered stomach that contains a group of special microorganisms. These microbes digest proteins and break amino acids down to obtain ammonia that they use for their own protein synthesis. The proteins produced by these microorganisms can also be used by the animals themselves. b) What part of the amino acid do the microorganisms remove to obtain ammonia (NH3)? [1 mark] The amount of amino acids was measured from different sections of the gut of cows when fed three different diets. The graph shows the results below: c) Does the data support the idea that microorganisms in the stomach are using the cow’s food to produce proteins? Support your answer with evidence from the information in the graph. [3 marks] d) Explain, using evidence from the graph, how having these microorganisms can be beneficial to the cows. [2 marks] e) Ammonia can be toxic in high concentrations. Suggest why it is important that cow feed includes a high carbohydrate content? [2 marks]