Biology A-Level: Pre Study Information

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1 Biology A-Level: Pre Study Information The minimum entry requirements for this course are: 1. Five or more A* to C GCSEs including English Language and Maths, 2. PLUS at least a B in English 3. PLUS at least a B in either Biology or Additional Science. It is a requirement that over the summer vacation prospective A-Level Biology students work through the Head Start study guide and complete the sample assessment. This must be submitted at the first Biology lesson. 1. CGP Head Start to A-Level Biology ISBN max cost 5.00 (may be cheaper on Amazon) Additionally, students must purchase the first of the two text books required for next year at the earliest opportunity: 2. Salters-Nuffield AS/A level Biology ISBN max cost (may be cheaper on Amazon) There will be an admission test after the first two weeks of the course that will also test the aspects of GCSE Biology. If students do not pass this assessment they will be asked to leave the course. The test will be a mixture of multiple choice questions and structured long answer questions. The material examined has been covered in GCSE Biology and is reinforced in the CGP Head Start to A-Level Biology workbook.

2 Summary sheet 1: Cell structure Prokaryotes are single celled organisms, including bacteria. They are simpler and smaller than Eukaryotic cells. Bacterial cells have: no nucleus with circular DNA free in the cytoplasm cell wall made from peptidoglycan no membrane-bound organelles small ribosomes. Eukaryotic cells include animal and plant cells. They are larger and more complex than prokaryotic cells. Animal cells have: linear DNA contained inside a nucleus no cell wall larger ribosomes and many membranebound organelles including mitochondria where aerobic respiration occurs and endoplasmic reticulum and golgi which are involved in the processing of proteins. Plant cells have the same organelles as animal cells but they also have: a cell wall a large vacuole containing cell sap chloroplasts for photosynthesis. greater detail Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 21

3 Summary sheet 2: Mitosis Mitosis results in the production of two genetically identical diploid body cells. It occurs during growth, repair and asexual reproduction. Mitosis occurs during the cell cycle. The cell cycle consists of a period of cell growth and DNA replication known as interphase and then a period of cell division called mitosis followed by cytokinesis where the cytoplasm divides and the cell membrane constricts to form the two daughter cells. Mitosis is broken down into stages prophase, metaphase, anaphase and telophase, followed by cytokinesis. 22 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

4 Summary sheet 3: Microscopy Magnification is how much bigger the image is than the specimen on the microscope slide. The size of the specimen can be calculated using the formula: length of the specimen = length of the image magnification With a light microscope the magnification is the combination of the magnification of the objective lens and the eye piece lens. For example a 40 objective lens and a 10 eye piece lens produce a total magnification of 400. When you are doing magnification calculations you must have all the lengths in the same units. 1 cm 10 mm 1 mm 1000 m 1 m 1000 nm Calculation Calculate the actual size of a cell with a diameter of 8 mm using 100 magnification. Actual size = = 0.08 mm = 80 m Resolution is a measure of how easy it is to distinguish between two points that are close together i.e. how much detail can be distinguished. Electron microscopes have a better resolution than light microscopes so they can see more detail. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 23

5 Summary sheet 4: Diffusion, osmosis and active transport Diffusion Liquid and gas particles are constantly moving which causes particles to move from an area of high concentration to an area of low concentration. Observing the process of diffusion. If the beaker is left to stand the random motion of both the water and the purple manganite(vii) ions will ensure they are eventually evenly mixed. Small particles can diffuse across cell membranes and no energy is required. Some molecules, such as glucose, are too large to diffuse across the cell membrane so they must be helped by carrier proteins. Each molecule has its own carrier protein that allows the molecule through the cell membrane without the need for energy. This is known as facilitated diffusion. Facilitated diffusion acts as a ferry across the lipid membrane sea. But this is a boat with no oars, sails or engine it can only work when the tide (the concentration gradient) is in the right direction. Osmosis Osmosis is the diffusion of water molecules from an area of higher concentration of water molecules to an area of lower concentration of water molecules across a partially permeable membrane. Active transport Active transport uses energy to transport substances across membranes from an area of lower concentration to an area of higher concentration 24 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

6 Summary sheet 1: Protein synthesis A gene is a sequence of DNA which codes for a protein. Proteins are synthesised in a two-step process transcription and translation. Transcription takes place in the nucleus and translation takes place at the ribosome. A complementary mrna strand is made using the DNA as a template. The mrna leaves the nucleus and attaches to the ribosome in the cytoplasm. A triplet of bases on the mrna (a codon) code for specific amino acids. The amino acids are delivered to the ribosome by trna. Peptide bonds are formed between the amino acids to make the polypeptide. The DNA gene sequence is ACA CGG AAA CCT GAC. The mrna sequence is UGU GCC UUU GGA CUG. This codes for the amino acid sequence is: Cys-Ala-Lys-Gly-Leu The protein folds into a specific structure. For enzymes this means that the active site forms a specific shape that binds specific substrates. 34 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

7 Summary sheet 2: Enzymes activity Enzymes are biological catalysts that speed up chemical reactions. Enzymes work by reducing the amount of activation energy needed for the reaction to occur. The active site of the enzyme is where the substrate binds. It has a specific shape which means enzymes can only bind to a specific substrate. The substrate binds to the active site forming an enzyme-substrate complex. The reaction is catalysed and the products released. Different factors can affect how quickly the enzymes work. These include temperature, ph, enzyme concentration and substrate concentration. As temperature increases there is more chance of a collision between the enzyme and substrates, as they have more kinetic energy. This continues until the optimum temperature where the rate of reaction is highest. As the temperature continues to rise the enzyme denatures, as the active site changes shape, when bonds holding the protein together break. Enzymes also have an optimum ph, above and below the optimum ph the enzyme denatures. As the substrate concentration increases there is more chance of a collision between the substrate and the enzyme. The rate of reaction increases until all the actives sites are occupied. The rate of reaction increases as enzyme concentration increases until all the substrate is bound to an enzyme. In practical situations you can sometimes measure the amount of product formed over time. The initial rate of the reaction for an enzyme can be calculated by measuring the gradient of the graph. If the line is curved a tangent to the curve can be used : gradient = y x. Amount of product x y Time Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 35

8 Summary sheet 1: Heart and lungs The left side of the heart pumps oxygenated blood from the lungs around the body. The blood enters the left atrium from the pulmonary vein. It flows through the atrioventicular or bicuspid valve to the left ventricle. The blood is then pumped into the aorta, through a semi-lunar valve, and around the body. The right side of the heart pumps deoxygenated blood from the body back to the lungs. The blood returns from the body to the right atrium via the vena cava. It flows through the atrioventicular or tricuspid valve to the right ventricle. The blood is then pumped into the pulmonary artery, through a semi-lunar valve, and to the lungs. The atrioventricular valves between the atrium and ventricles open to allow blood to flow from the atrium into the ventricles and close when the pressure in the ventricles rises to prevent back flow. The semi-lunar valves in the aorta and pulmonary artery open to allow blood from the ventricles to flow into the arteries. They close to prevent backflow into the ventricles as the heart relaxes. Oxygen enters the blood in the alveoli of the lungs. Oxygen in the alveolus is at a high concentration and it diffuses down the concentration gradient into the blood which has a low concentration of oxygen. This low concentration is maintained because the blood is moving and carries the oxygen away. The walls of the alveolus and capillaries are only one cell thick. This creates a short diffusion distance between the alveolus and the blood allowing a high rate of diffusion. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 43

9 Summary sheet 2: Circulatory system Blood flows around the body via a network of arteries, veins and capillaries. The double circulation system of mammals means that blood flows through the heart twice in one complete cycle of the body. The pulmonary system pumps blood around the lungs and the systemic system pumps blood around the rest of the body. Arteries carry blood away from the heart. The vessel walls are thick and muscular with elastic fibres to withstand the high pressure generated by the heart. Veins carry blood from capillary beds back to the heart. The blood is at low pressure and the walls of the vessels are relatively thin with less elastic fibre. The contraction of muscles help push the blood though veins and the vessels have valves to prevent backflow. Capillaries are thin vessels that form capillary networks around tissues. They allow the exchange of substances such as oxygen, glucose and waste materials between cells and the blood. 44 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

10 Appendix 3: Exam practice These are higher exam questions from the Biology GCSE specification. They relate to the topics covered in AS Biology and can be used to refresh the knowledge from KS4. 1 Mutations can occur in genes. Mutations can cause genetic disorders in humans. Phenylketonuria (PKU) is a genetic disorder caused by a gene mutation. People with PKU produce an inactive enzyme. The normal base sequence and the mutated base sequence which can cause PKU are shown below. normal base sequence... C T C G G C C C T mutated base sequence...c T T G G C C C T a Describe how the changes that have occurred in the mutated base sequence produce an inactive enzyme. b Explain how the mutated base sequence will result in an inactive enzyme being produced during protein synthesis. (6 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 79

11 2 A DNA molecule consists of two strands coiled to form a double helix. a Describe how the two strands of a DNA molecule are linked together. b The bar chart shows the percentage of guanine and thymine in a sample of DNA. Complete the bar chart to show the percentage of adenine and cytosine in the sample. c The diagram shows part of one DNA strand. i Complete the empty boxes to show the mrna strand coded for by this DNA strand. 80 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

12 ii State the maximum number of amino acids that are coded for by this DNA strand. d Name the structure where translation occurs. 3 Proteins are made up of amino acids. a The table shows the DNA bases that code for some of the amino acids found in proteins. DNA bases AAA AAC CAA TAC TTC Amino acid Phe leu val met lys Part of the DNA coding for a protein is: T A C C A A T T C i State the order of amino acids coded for by this sequence of DNA. ii These amino acids will be joined together during protein synthesis. During which stage of protein synthesis will this take place? iii Complete the sentence by putting a cross ( ) in the box next to your answer. Amino acids are joined together A at the membrane B in the mitochondria C in the nucleus D at the ribosome Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 81

13 b DNA can code for the amino acids in the active site of an enzyme. Explain the role of the active site of an enzyme. c Mutations can occur in DNA. Describe what effect a mutation could have on the action of an enzyme. (3 marks) 4 There are many different types of cell in the human body. a Complete the sentence by putting a cross ( ) in the box next to your answer. An embryonic stem cell can A differentiate into any type of cell B differentiate into only one type of cell C only be obtained from embryos D only produce haploid cells b Describe how the structure of a red blood cell is related to its function. (3 marks) 82 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

14 c Describe the function of platelets. d Mitosis and meiosis are types of cell division. Compare these two types of cell division. (6 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 83

15 5 Yeasts are microorganisms that are used in the brewing and baking industries. The diagram shows a yeast cell. a i State two ways in which the structure of this yeast cell differs from the structure of a bacterial cell. ii Plant cells can produce glucose. Suggest why yeast cells cannot produce glucose. 84 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

16 b The table shows the number of different components found in the blood of a healthy person and the blood of two other people. i Calculate the difference in the number of white blood cells per dm 3 of blood between the healthy person and person A. ii Describe the functions of white blood cells. iii Person B has a low number of red blood cells compared to the healthy person. Suggest an effect this may have on person B. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 85

17 6 Corals are animals that live on the sea bed. The photograph shows some species of coral. After fertilisation, mitosis takes place to form an embryo. The embryo develops into new coral. a Describe mitosis. (3 marks) b Describe how the embryo develops into new coral. (3 marks) 86 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

18 7 Cells in a human body can be haploid or diploid. When an egg cell combines with a sperm cell a fertilised egg, known as a zygote, is formed. a Which row of the table gives correct information about the egg cell, the sperm cell and the zygote? Put a cross ( ) in the box next to your answer. egg cell sperm cell zygote A diploid diploid haploid B diploid haploid diploid C haploid diploid haploid D haploid haploid diploid b The single cell of the zygote divides into two cells in 15 hours. These cells continue to divide in this way to form an embryo. This diagram shows an embryo with 32 cells. Calculate the length of time it takes the single cell of the zygote to form an embryo with 32 cells. c The cells of this embryo are genetically identical. Explain how these genetically identical cells are produced. (3 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 87

19 8 a Tigers are classified as vertebrates. The binomial name for the tiger is Panthera tigris. i Complete the sentence by putting a cross ( ) in the box next to your answer. The word Panthera in the tiger s binomial name refers to its A class B genus C order D species ii State the phylum that includes mammals such as tigers. b Bacteria are classified as prokaryotes. State two characteristics of prokaryotes Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

20 c Explain why it is difficult to classify some living organisms. d Describe how scientists classify vertebrates into different groups. (6 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 89

21 9 Charles Darwin studied the variety of finches on the Galapagos Islands. He used this information to develop his theory of evolution. Some of the finches are shown in the diagram. a i State the genus and the species of the large cactus ground finch. ii Suggest how the size and shape of their beaks enabled all of these types of finches to survive. 90 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

22 iii Complete the sentence by putting a cross ( ) in the box next to your answer. Darwin's finches are an example of speciation due to A selective breeding B geographic isolation C hybridisation D the development of ring species b Suggest how these species of finches could have evolved. (3 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 91

23 10 a Gas exchange in the air sacs of the lungs takes place in a similar way to gas exchange between body cells and capillaries. Each of these air sacs are surrounded by blood capillaries. The diagram shows one air sac. i Describe how oxygen is transported from the air sac into the surrounding blood capillary. ii Complete the sentence by putting a cross ( ) in the box next to your answer. The blood transports oxygen to body cells. Oxygen is used by body cells when A energy is released during respiration B energy is released from carbon dioxide C glucose is produced during respiration D energy is taken in during respiration 92 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

24 b The graph shows how the heart rate of a person changes during and after aerobic exercise. i The volume of blood leaving the heart during one heart beat at 25 minutes is 0.07 dm 3. The person s cardiac output can be calculated using the equation: cardiac output = stroke volume heart rate Calculate the cardiac output of this person at 25 minutes. (3 marks) ii Explain the trend shown by the graph between 5 and 25 minutes. (3 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 93

25 c Anaerobic respiration takes place when the muscle cells are not supplied with enough oxygen. Give the word equation for anaerobic respiration. 11 This diagram shows a human heart. a i Draw an arrow onto the diagram to show where oxygenated blood enters the heart. ii Suggest how the blood flowing through the pulmonary artery would be different from the blood flowing through the aorta. iii Describe the role of the valve labelled on the diagram. 94 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

26 b Heart disease can significantly reduce cardiac output. i Complete the sentence by putting a cross ( ) in the box next to your answer. Cardiac output is the volume of blood leaving the A atrium every heart beat B atrium every minute C ventricle every heart beat D ventricle every minute ii A reduced cardiac output would affect the performance of an athlete. Explain the effects that a reduced cardiac output would have on the muscle cells of an athlete. (6 marks) Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 95

27 12 In an investigation, a person ran at different speeds. The graph shows the concentration of lactic acid in the blood and the heart rate of this person while running. a When the running speed is 22 km h 1, the stroke volume of the runner is 0.18 dm 3. Calculate the cardiac output in dm 3 per minute of the runner using the equation. cardiac output = stroke volume heart rate b Complete the sentence by putting a cross ( ) in the box next to your answer. When the heart rate is at its maximum the concentration of lactic acid in the blood is A 11.2 mmol dm 3 B 12.8 mmol dm 3 C mmol dm 3 D mmol dm 3 96 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

28 c Complete the sentence by putting a cross ( ) in the box next to your answer. The graph shows that A as the heart rate increases the concentration of lactic acid increases B as the concentration of lactic acid increases the heart rate decreases C the concentration of lactic acid increases as running speed increases D the concentration of lactic acid is not dependent on heart rate d Explain why the concentration of lactic acid changes at running speeds greater than 18 km h 1. (3 marks) 13 The photograph shows a blood smear from a healthy person. a Name the two types of blood cells, X and Y, shown in the photograph. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 97

29 b Complete the sentence by putting a cross ( ) in the box next to your answer. The function of the cells labelled X is to A engulf bacteria B produce antigens C transport carbon dioxide D transport oxygen c Measure the diameter of the cell labelled Z to the nearest mm. d The cell labelled Z is magnified 900. Calculate the actual diameter of the cell labelled Z in m. 98 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

30 14 a Substances in the soil are taken up by plant root hair cells. The diagram shows the direction of movement of two substances A and B across the cell membrane of a root hair cell. i Name process X. ii Name process Y. iii Mineral ions are taken up by the root hair cells of plants. Name the type of vessel that transports these mineral ions through the plant. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 99

31 b A student investigated osmosis in a courgette. The photograph shows a courgette. The student weighed pieces of courgette and placed them in five different concentrations of sugar solution. After one hour she dried and reweighed the pieces of courgette. She calculated the percentage change in mass. The graph shows the results of this investigation. i Draw a line of best fit on the graph. ii Use your line of best fit to estimate the concentration of sugar solution in moles per dm 3 that would result in no change in mass. 100 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

32 iii Explain why there was an increase in the mass of the courgette in the sugar solution at 0.2 moles per dm 3. (3 marks) 15 Photograph A shows a Coleus plant that has wilted due to lack of water. If this plant is given some water it will recover and stand upright again. Photograph B shows the plant after it has been watered. a Describe how a plant takes in water from the soil. Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 101

33 b The soil surrounding the roots of the Coleus plant contains water with a higher concentration of dissolved mineral ions than the plant cell vacuole. Which row of the table gives the method of transport of mineral ions into the plant cell of this Coleus and the type of vessel which transports mineral ions to its leaves? Put a cross ( ) in the box next to your answer. Method of transport into the plant cell Type of vessel which transports mineral ions A Active transport Phloem B Active transport Xylem C Diffusion Phloem D Diffusion Xylem 16 This diagram shows three duckweed plants in a beaker of distilled water. a Explain how the water moves into these plants. (3 marks) 102 Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free.

34 b Salt was added to the water in the beaker to form a salt solution. Explain how the salt solution would affect the movement of water into and out of the plant. c Complete the sentence by putting a cross ( ) in the box next to your answer. When the concentration of mineral ions in the soil is greater than in the root hair cell, mineral ions are transported into the root hair cells by A diffusion B osmosis C respiration D transpiration Pearson Education Ltd Copying permitted for purchasing institution only. This material is not copyright free. 103