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AS and A Level: Exchange, Transport & Reproduction

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Five tips on presenting and analysing data from core practicals

  1. 1 Raw data should be presented in a table with clear headings. All table column and row headings should contain units and readings should all be recorded to the same decimal place.
  2. 2 Raw data should be processed to provide descriptive statistics such as the mean and standard deviation.
  3. 3 Present data using the relevant graph type. Ensure that you add error bars showing either standard deviation or standard error.
  4. 4 When describing trends and patterns, manipulate data to calculate the size of key changes. For example, absorbance increases by 0.09 absorbance units between 10◦C and 40 ◦C. Preferably express the change as a percentage increase or decrease. Do not simply quote points, eg at 10 ◦C absorbance was 0.01 and at 40 ◦C it had gone up to 0.1 absorbance units.
  5. 5 Discuss each phase of the graph. For example if there is a slow increase, followed by a rapid increase, and then the graph levels off and shows a decrease, discuss these four key phases. Do not give detailed descriptions of each small fluctuation. The trends and patterns are the important things.

Meiosis and Mitosis facts

  1. 1 Meiosis generates gametes/sex cells, whereas mitosis is for growth/repair and generates daughter cells identical to the parent cell.
  2. 2 During Meiosis chromosome number is halved producing haploid gametes with a single copy of each chromosome. During Mitosis chromosome number is maintained producing diploid daughter cells with maternal and paternal copies of each chromosome, i.e. homologous chromosome pairs.
  3. 3 Before mitosis and meiosis all chromosomes are copied as part of interphase. At the end of interphase there are two identical copies of every maternal chromosome and every paternal chromosome, so chromosome number has doubled (i.e. at the end of interphase a human cell contains 46 x 2 = 92 chromosomes). The identical copies of chromosomes are referred to as sister chromatids and they are joined by a centromere.
  4. 4 In meiosis, genetic variation is generated by crossing over during prophase 1, and independent chromosome assortment at metaphase 1 and metaphase 2. During crossing over maternal and paternal chromosomes cross each other, and break at points known as chiasma. Maternal and paternal alleles below the chiasma change places so that the paternal chromosome contains maternal alleles and vice-versa. During metaphase 1 and 2, maternal and paternal chromosomes align randomly on one side of the equator. As the maternal and paternal chromosomes can align on either side, different potential chromosome combinations can occur.
  5. 5 The events in metaphase, anaphase and telophase are identical in both mitosis and meiosis 1 and 2. In mitosis a single division occurs, whereas in meiosis cells undergo 2 meiotic divisions.
    a) During meiosis 1, maternal and paternal sister chromatids are separated so that 1 cell contains both maternal sister chromatids of a pair and the other contains both paternal sister chromatids.
    b) During the second meiotic division, sister chromatids are separated. The gametes that result contain only 1 chromosome from each pair, i.e. they are haploid.

How to evaluate experimental methods

  1. 1 When evaluating the reliability of experimental methods, always consider whether all variables other than the independent variable have been adequately controlled. If a variable cannot be controlled has it been monitored to establish any effect it might have?
  2. 2 All experiments must be repeated to establish reliability. Has the experiment been repeated at least three times? Preferably you should repeat it more than 3 times.
  3. 3 What does the standard deviation suggest about the spread of the data? If the mean is 5, but the standard deviation is 3, readings vary from the mean considerably. This suggests that the mean does not represent the actual readings.
  4. 4 How precise are the measurements? If a balance used to measure change in mass only measures to 0.1 g then the reading could be 0.12 g, 0.15g, or 0.18g etc.
  5. 5 How accurate are the readings? If equipment is re-used for different repeats for example, cross contamination could affect the accuracy of subsequent readings. If tubes are shaken different amounts, different volumes of gas could be released. Consider all potential sources of error and discuss how the procedure could be improved to reduce these sources of inaccuracy.

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  1. A colorimetric method for the estimation of glucose in solution

    I will then shake the test tube to mix up the liquids so that the concentration is the same through out the liquid When measuring out amounts of liquid I will make sure that the bottom of the meniscus of the circle of the top of the liquid is on the measuring line. I will use a 10cm3 pipette to put Benedict?s reagent in to 13 boiling tubes and put them in to a water bath at 100oC for 3 minutes to warm up.

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  2. the Effect of Temperature on an Immobilised Digestive Enzyme

    0.01% 0.13% seconds 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.50% 0.38% 2.00% 1.00% 1.50% Analysis Two runs of each glucose percentage were carried out. The level of glucose was measured every 30 seconds, untill no more glucose was produced. Then the mean glucose concentration was worked out to ensure a fair test. To improve this experiment furher more runs could have been made of each temperature and more temperatures could have been included.

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  3. Diabetes is a common disorder of metabolism in which the amount of glucose or sugar in the blood is too high, suffocating the bodys cells, and damaging the sufferers health. Discuss this illness.

    Though there is no cure for diabetes, proper insulin intakes and other cures together with a correct diet enable most diabetics to live virtually normal lives with few side effects, although their mortality rate is higher. A common symptom of diabetes is weight reduction caused by the loss of fluids and fat in the body's cells due to high sugar levels suffocating the cells. Other symptoms are passing high amounts of urine, amplified thirst, vision problems, limb numbness, genital itching, ceased menstruation in women; and a frequent boils and skin infections.

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  4. To investigate the effect of sucrose solution on osmosis.

    I am doing this experiment in room conditions. Potatoes must be cut very carefully to get a correct result. I shall cut 6x5cm bars using a scalpel to cut and a ruler to measure. Then I shall number each bar, 1, 2, 3, 4, 5, or six. I shall then number each test tube in the same way. Carefully, I shall use the pepite to measure 10ml of each kind of solution into each test-tube. I shall put the different solutions in this order: Test-tube 1: 0.0 mol of sucrose solution Test-tube 2: 0.2 mol of sucrose solution Test-tube 3:

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  5. Drinks For Diabetics

    This increase causes a change in blood water potential and harmful increases in blood pressure. The amount of glucose in solution can be determined using Benedict's reagent, an alkaline copper solution that reacts with the reducing carbonyl group (C=O) in some carbohydrates. All monosaccharides and the disaccharides maltose and lactose are reducing. The concentration of reducing carbohydrate can be determined from standard solutions of known glucose concentration. Aim: To carry out an experiment to determine which drinks would be safest for a diabetic person to drink without them having to worry about insulin levels.

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  6. An experiment to find out the effect of different sucrose solutions on the growth of yeast.

    Volume of the solution - The volume of solution in each of the test tubes and chronicle flasks must be all the same as other wise the experiment would not be a fair test. iii) The amount of yeast - The amount of yeast put into each of the chronicle flasks must be the same as it would not be a fair test. iv) The sucrose concentration - It must be a known concentration varying from a high concentration to a low concentration of sucrose between the six test tubes, so it is able to see in which concentration the yeast grows best in.

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  7. Diffusion and osmosis

    Very few particles leave an area of low concentration to go to an area where the concentration is higher. * This creates a diffusion gradient - the result is that particles diffuse from an area of high concentration to an area of low concentration. Diagram Of Diffusion 2. Examples of diffusion Have a look at these examples of a diffusion gradient.You need to learn at least one example. Place Particles move From To Gut Digested food products Gut cavity Blood in capillary of villus Leaf Oxygen Chloroplast Air spaces in mesophyll Example Particles continue to move from high to low concentration for as long as there is a concentration gradient.

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  8. Blood - Its structure and components

    It might seem like plasma is less important than the blood cells it carries. But that would be like saying that the stream is less important than the fish that swims in it. You can't have one without the other. Besides water, plasma also contains dissolved salts and minerals like calcium, sodium and magnesium and a complex mixture of proteins, vitamins and hormones. Microbe-fighting antibodies also travel to the battlefields of disease by hitching a ride in the plasma. Without plasma, the life-giving blood cells would be left without any transportation. Never underestimate the importance of plasma.

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  9. How does changing sucrose concentration affect the process of osmosis and therefore plant material?

    As the water passes through the membrane into the tube, the level of sugar solution in the tube visibly rises. A semi-permeable membrane that may be used for such a demonstration is the membrane found just inside the shell of an egg, that is, the film that keeps the white of the egg from direct contact with the shell. In this demonstration, the water moves in both directions through the membrane; the flow is greater from the vessel of pure water, however, because the concentration of water is greater there, that is, fewer dissolved substances exist in this solution than in the sugar solution.

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  10. Investigating Anaerobic Respiration in Yeast

    Factors to Consider I will carry out an investigation into one of the following factors to see how it effects the amount of anaerobic respiration that the yeast performs. Factors affecting rate of respiration: * Concentration of glucose solution * Temperature that fermentation is carried out under * Quantity of yeast Concentration of Glucose solution - this will not speed up the Temperature that fermentation is carried out under - yeast breaks the glucose down using enzymes and enzymes work most efficiently at certain temperatures.

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  11. To Investigate the Effect of Substrate Concentration On Yeast Respiration

    A graph will be plotted of the different concentrations against the time taken. The gradient of the graph will determine the rate of respiration. Background Information Yeast is a fungi Formula Yeast is able to respire in Glucose because the shape of its active site matches the shape of the Glucose molecule. This type of reaction where a molecule is broken down into smaller pieces is called an Anabolic Reaction. Apparatus. 1. 250 cm3 Glass Beakers 2. Glass Thistle Funnel 3. Graduated Measuring Cylinder 4. Cork Borer 5. 250 cm3 Glass Cylinders. 6.

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  12. Water Potential of Potato Tuber Cells: The Density Method

    Then, using a separate graduated syringe in each case, place 5cm3 of the appropriate solution in each test tube. Pipette 3cm3 of sucrose solution with each sucrose concentration into other test tubes and label them. Place one drop of methylene blue in each of these test tubes. This will colour the solution but not affect its water potential. These are to be shared among the class. Next, using a cork borer and a razor blade, prepare a solid cylinder into thirty discs of approximately equal (2mm) thickness. Note the time and place four of the potato discs into each of the seven 3 cm3 test tubes of sucrose solutions.

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  13. The Importance of Controlling Blood Glucose

    They affect liver, fat tissue and muscle. Insulin is released when blood sugar is too high. It stimulates the removal of glucose in the blood. Glucagon is released when blood sugar is too low. It stimulates the release of glucose into the blood. Insulin controls the conversion of glucose to glycogen; glucagon controls the conversion of glycogen to glucose. Glucose is a simple sugar which is soluble in blood plasma and the cells cytoplasm.

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  14. Dissolving Sugar

    We will do the experiment at 20?c, 30?c, 40?c, 50?c, 60 ?c, 70?c and 80?c. Each experiment will be completed as quickly as possible to make the experiment a fair test, as the temperature will quickly drop. Once the solution is saturated we will measure the weight of the remaining sucrose and take that number away from the original 25g, this will then tell us the amount of dissolved sucrose. To keep the test as fair as possible, all the variables will remain constant (except for the temperature). As I previously stated it is important to complete the experiment as quickly as possible so the results are as accurate as can be.

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  15. Factors that Affect the Rate of Yeast of Activity

    In this experiment the yeast and substrate (glucose) will stay constant in all five beakers. The five beakers will be filled with 50ml of water, with the same amount of yeast. We will then add the substrate. The amount of glucose will be 2 molar, which is equal to 19.8g. I worked this out by the following calculations; Mr 198.17 Molecular mass of glucose 198.17 - X 20ml = 3.9g = 1 molar 1000 3.9 x 2 = 7.9g � 20ml, 2 molar My five different temperatures will be 0�c, room temperature, 30�c, 40�c and 50�c.

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  16. Investigating Osmosis In Potato Cells

    Next we labelled 6 boiling tubes: 1 to 6. Then we patted the chips dry, measured their length with a ruler and measured their mass on an electronic scale and recorded these measurements in a table (results). We filled the tubes with the required solution: Tubes 1 and 2: 0.4 M sucrose Tubes 3 and 4: distilled water Tubes 5 and 6: 1.0 M sucrose After leaving them for 3 hours we recorded how the mass and the length of the chips had changed and compared these measurements with the initial recordings.

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  17. Lymphedema development in the human body

    It can progress into a troublesome disorder in time however at first it will seem to come and go. For example in the mornings it may be at minimal stage and during the day time it will become larger.

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  18. The Process of Osmosis and its Importance to Living Organisms.

    If blood cells, for example, are placed in contact with an isotonic solution, they will neither shrink nor swell. However, if the solution is hypertonic, the cells will lose water and shrink. A real life example of such an event occurring is the consumption of saltwater. Saltwater from the ocean is hypertonic to the cells of the human body; the drinking of ocean water dehydrates body tissues instead of quenching ones thirst. If the solution is hypotonic, for example deionised water, the cells will swell; the osmotic pressure that is developed may even be great enough to rupture the cell membrane.

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  19. Excretion and the functioning of the kidneys

    Urea is then transported by the blood from the liver to the Kidneys where it forms part of urine. The Kidney The Kidney has two main functions, it removes metabolic waste from the body through the process of excretion and it regulates the water and ion content in the blood. The excretion is of a dilute solution called urine which contains urea, mineral ions, water and other foreign chemicals from the blood. The two kidneys have a very extensive blood supply and the whole blood supply passes through the kidneys every five minutes ensuring that the waste materials don?t build up.

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  20. Histology of Blood vessels

    The wall of the arterioles contains less elastic fibers but more smooth muscle cells than that of the aorta. Arteries carry oxygen-rich blood at high pressure, so they are tough on the outside and smooth on the inside. The arteries have three layers and the smoothness of the inner layer enables blood to flow easily with no obstacles. Arteries carry oxygen-rich blood at high pressure, so they are tough on the outside and smooth on the inside.

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  21. Should We Adhere To A Mediterranean Diet or An UK Diet In Order To Obtain A Healthy Heart?

    After many researchers and biologists proved that the Mediterranean diet was much healthier, they conducted trials and studies on many different people. A study called PREDIMED-Reus was conducted on 418 non-diabetic Spanish people. (1) They were aged 55 to 80 years old. They required a yearly oral glucose tolerance test and they were put into randomized groups. The groups were: 1. A low fat diet (Control Group) 2. A Mediterranean diet with virgin olive oil- 1 litre per week 3.

    • Word count: 497

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