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AS and A Level: Molecules & Cells

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  1. An Experiment To Investigate The Effect Of Temperature on The Action Of The Enzyme Trypsin On Casein

    The temperature is read on a temperature in the range of 0- 60�C, and readings taken to the nearest increment, i.e. 0.5 of a degree. All should be turned on and left for at least 20 minutes as to allow the temperatures of each bath to equilibrate. Pipette 5 cm3 of the Casein suspension into one test tube, label this Casein room temperature, and also pipette 5 cm3 of the Trypsin solution into another test tube and label this Trypsin room temperature.

    • Word count: 1082
  2. Investigate the effect of temperature change on the rate of hydrolysis of starch catalsed by amylase

    Amylase is an enzyme; it is present in the digestive systems of many animals. Amylase speeds up the breakdown of long chain starch molecules in smaller chains of maltose. Each enzyme has a specific active site, which connects with specific substrates. It is exactly the right size and shape as part of this substrate (in the case of amylase this is starch). When a substrate molecule slots into the active site, the enzyme 'tweaks' the substrate molecule, pulling it out of shape and making it split into product molecules. This is due to the hydrogen bonds that break.

    • Word count: 1166
  3. To investigate the effect of temperature on enzyme activity

    Prediction An enzyme is a protein molecule that speeds up chemical reactions in all living things. Without enzymes, these reactions would occur too slowly or not at all, and no life would be possible. All living cells make enzymes, but enzymes are not alive. Enzyme molecules function by altering other molecules. Enzymes combine with the altered molecules to form a complex molecular structure in which chemical reactions take place. The enzyme, which remains unchanged, then separates from the product of the reaction. Therefore, an enzyme is a sort of biological catalyst. Using existing scientific knowledge, it is predicted that as the temperature is raised to 30oC, 35oC, and 40oC, this is where the greatest reaction will be seen.

    • Word count: 932
  4. Enzymes Investigation

    When the molecule is broken up the enzyme remains the same shape. ---picture of this--- Enzymes work best at low temperatures (from 5�C-45�C). The optimum temperature for enzymes is between 37�C- 40�C (body temperature). They denature at higher temperatures because there is too much energy causing too many collisions. They are important because they break up, large, insoluble, molecules into smaller, soluble molecule, which then can go on and be used by the body. This table shows some different types of enzymes and their job: Enzyme What it breaks down Lipase Fats into fatty acids Protease Protein into amino acids Amalase Starch Carbohydrase Carbohydrates into glucose The enzyme I will be using in the practical is catalase.

    • Word count: 762
  5. Amylase Investigation

    Enzymes are responsible here too; they control the absorption of radiant energy. Yeast use enzymes to levin bread and ferment sugar into alcohol. Bacteria use enzymes to break down cellulose fibre in the stomachs of cows and the stomachs of termites. Reproduction, growth, metabolism, synthesis, are all enzymes regulated reactions in living things. Enzymes are made from amino acids, and they are proteins. Because they are made up of proteins, they are sensitive to heat, pH and heavy metal ions.

    • Word count: 9104
  6. The Effect of the Concentration of an Inhibitor on The time taken for the Enzyme to Fully Breakdown the Substrate

    Amylase digests starch by catalysing hydrolysis, which is splitting by the addition of a water molecule. Therefore starch plus water becomes maltose (which is equivalent to two joined glucose molecules). There are two kinds of amylase enzymes. Alpha-amylase is found in saliva and is called ptyalin. This can carry on working in the stomach for several hours (and can digest up to 40% of starch under correct conditions of stomach acidity and food solidity). The other kind is called pancreatic amylase and is secreted in pancreatic juice, into the small intestine or ileum. Inhibitors are chemicals, which reduce the rate of an enzyme-catalysed reaction, and they do so by altering the shape of the active site.

    • Word count: 2531
  7. Enzymes in the Starch and Sugar Industry

    This was a major breakthrough, which led to the birth of a multi-billion dollar industry in the USA for the production of high fructose syrups. Using enzymes for starch modification, it is important that by choosing the right enzymes and the right reaction conditions, valuable enzyme products can be produced to suit virtually any specific need in the food industry. Syrups and modified starches of different compositions and physical properties are obtained and used in a wide variety of foodstuffs, including soft drinks, confectionery, meats, baked products, ice cream, sauces, baby food, canned fruit, preserves and more.

    • Word count: 1967
  8. Effect of Concentration of Substrate on Enzymes

    is used (or another indicator that changes at pH 7 of after) it's on the flatter part of the graph where there is little difference between each pH. It is therefore harder to see when the change occurs because it is so gradual. Each indicator has it's flaws and is better to use the most accurate and easiest to measure (screened methyl orange). This though would show a pH change at pH6 and would not show the end of the reaction. The end or rate of reaction can be measured in many ways.

    • Word count: 2436
  9. An investigation into the effect of temperature on the permeability of cell membranes

    The cell membrane also uses the process o active transport, which requires proteins with the aid of cell energy. A possible way of doing this is sown below: It is a carrier protein that rotates, transferring substances from inside the call to outside the cell. A number of things can affect the permeability of a cell membrane, for example pH and temperature. The later is what I will be investigating in this experiment. When a plasma membrane is exposed to these conditions the membrane loses it the extent of its selective permeability. This happens because when it is exposed to high enough temperatures the protein cells are denatured this makes them lose their shape and exposes holes in the lipid layer.

    • Word count: 1756
  10. Explain how a series of impulses are initiated and transmitted along a neurone and across a synapse.

    This depolarisation is known as an action potential. At the end of depolarisation the sodium channels are closed and excess Na+ ions are pumped out of the axon by a sodium pump.

    • Word count: 308
  11. Enzyme structure and function

    Globular is its quaternary structure feature, and unlike fibrous proteins, globular proteins are spherical and highly soluble. The primary structure of a protein (and likewise, an enzyme) is the type and sequence of amino acids. All amino acids share a basic structure of an amine group and a carboxylic acid group. What makes them different is a third group 'R' which can be anything from a simply hydrogen molecule to form glycine - to glutamine a slightly more complex molecule. The secondary structure is how each polypeptide chain is 'bonded' to the chain next to it, to form either an ?-helix or a �-pleated sheet.

    • Word count: 1721
  12. Investigation Into the effect of Temperature on Respiration

    Simultaneously hydrogen ions are transferred to the hydrogen acceptor NAD, which forms NADH. AcetylCoA reacts with oxaloacetate (4C). This reaction is caused by enzymes. The acetyl groups splits off, citrate (6c) is formed and coacetylcoenzyme A is released for reuse. In a series of reactions the citrate is converted back to oxaloacetate, which becomes available to repeat cycle. At certain points on the cycle two molecules are given off. This can be collected to measure the rate of reaction. A pair of hydrogens are removed and a molecule of ATP is made. The hydrogen atoms taken up by NAD, with the exception of one pair that is, are directly attached to FAD.

    • Word count: 1950
  13. Investigating The Activity Of The Enzyme Lipase On Milk

    This is called the Lock and Key Hypothesis because the enzyme (lock) and substrate (key) only fit into their own match. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. However, if an enzyme meets an inappropriate heat or pH level, it is denatured which results in a crucial change in shape so that the key (substrate molecule) can no longer fit into the lock (denatured enzyme).

    • Word count: 3587
  14. Biology Enzymes Coursework

    I will keep all these things the same, � The amount of yeast+ glucose and the amount of Methylene blue. � The amount of water used. � The apparatus, test tube, beaker, thermometer and timer. � I will use the same batch of methylene blue and yeast +glucose. I will keep all of these things the same in order to do a fair test. Scientific theory: I know that the more common enzymes work best at around 40.c. This is there optimum temperature.

    • Word count: 814
  15. The Effect of Enzyme Activity

    Trypsin digests proteins at specific points. It requires the remains prior to the cut site to be positively charged. Many things effect the enzyme activity which include the change of temperature and the change of pH scale. Aim Our aim is to find the optimum working temperature for the protease enzyme, trypsin. These enzymes will digest milk to turn it into a colourless liquid. Prediction I predict that the optimum working temperature of the protease enzyme will be 37?C, our body's average temperature. This has been predicted because the trypsin is contained, in the pancreas, in our bodies where it must work most efficiently.

    • Word count: 806
  16. The application of enzymes in industry and medicine

    In the modern textile industry enzymes are used increasingly in the finishing of fabrics and clothes. The main component of cotton and other natural fibres is cellulose. Whilst most of the fibres are arranged as long, straight chains some small fibres can protrude from the yarn or fabric. The correct application of a cellulse enzyme can remove these rough bumps giving a smoother, glossier brighter coloured fabric. This technique has become known as Biopolishing and results in not only a softer fabric but also improved colour brightness. The same process has recently been adapted and included in some laundry detergents.

    • Word count: 1534
  17. Changes in Temperature affecting Amylase and Starch

    using a pipette. Then, in two test tubes separately, heat 5ml of amylase solution and 10 ml of starch solution starch.

    • Word count: 309
  18. Osmosis Investigation

    * I left the potato strips in the tubes for 48 hours. I then came back and extracted the strips from their containers and dried off the excess solution. I then weighed the strips on the same scales and recorded the results in my table. Safety * All schoolbags must be placed under the table * Place lids on specimen tubes * Hang up all blazers and coats * Clear all tables * Make sure all containers are towards the middle of the table. * Do not run * Make sure the teacher supervises me when using the knife * Wipe up any spilt solution.

    • Word count: 1294
  19. Investigating the Effect of Glucose Concentration On the Rate of Reproduction of Yeast Cells

    In "http://esg-www.mit.edu:8001/cgi-bin/biosearch.pl?yeast", anaerobic respiration is called "http://esg-www.mit.edu:8001/cgi-bin/biosearch.pl?fermentation". These organisms are called facultative aerobes, because when oxygen is present, they respire aerobically, but if oxygen is absent, their respiration is purely anaerobic. In anaerobic respiration, as in aerobic respiration, the first step consists of breaking down glucose into pyruvic acid (see Box 1). However, the two processes differ considerably in the details of this step. In anaerobic respiration, there is no Krebs cycle. The end products of anaerobic respiration Box 1: Comparison between aerobic and anaerobic respiration (i)

    • Word count: 6363
  20. Investigating the “lock+key” hypothesis

    Amylase is an enzyme that reacts with starch converting it into glucose molecules. Aim To find out how enzyme concentration affects the rate of an enzyme controlled reaction Hypothesis I believe that the effect of increasing the concentration of the enzyme will increase the speed with which the enzyme-controlled reaction takes place. This prediction is correct according to the "Lock And Key" hypothesis explained earlier. There will be more enzyme molecules available in a given volume of amylase solution. This way more amylase molecules will be catalysed at the same time because each needs an enzyme molecule to catalyse it.

    • Word count: 1140
  21. The breakdown of hydrogen peroxide and how I can change the rate of reaction by altering the temperature.

    * Place hot plates in a safe and secure area to avoid burning oneself. Step by Step I will be altering the hydrogen peroxide to the following temperatures: 16?C, 20?C, 30?C, 35?C, 40?C, 45?C, 50?C, 65?C, 70?C I will be taking 2 results from each temperature to spot any anomalous results: 1) Set up the experiment as shown in the diagram, (including measuring 5g of celery into the conical flask.) 2) Place bottle of hydrogen peroxide in a small beaker of water and place on hot plate until correct temperature. 3) Pour 30ml of the hydrogen peroxide into the conical flask on top of the celery.

    • Word count: 2458
  22. Biology Coursework - Enzymes.

    Enzymes work by reducing the amount of activation energy required. Normally the reactions that take place need activation energy to get the molecules to react. Enzymes affect the amount of energy that is required. With enzymes, less activation energy is required to get the reaction started. Since this energy usually comes in the form of heat, the presence of enzymes means less heat is needed to spark off the reaction. This means reactions can readily take place in lower temperatures i.e. body temperature (37�c). This means there is more energy to go around so more reactions can take place at once.

    • Word count: 2206
  23. An investigation into the effect of increasing the concentration of salt solutions on potato cells.

    This process is called Osmosis. It is the diffusion of water molecules from a place where they are in a higher concentration (such as dilute sugar solution), to a place where the water molecules are in low concentration (e.g. concentrated sugar solution) through a partially permeable membrane. Cell membranes are like visking tubing. They will let some substance pass through them, but not others, working as a partially permeable membrane. This diagram illustrates a plant cell in pure water. Plant cells do not burst in pure water.

    • Word count: 3413
  24. Volume of oxygen given off in the reaction between catalase and hydrogen peroxide.

    The liquidised celery will be kept at room temperature, as this should prove warm enough for the reaction to occur, if the liquidised celery was to be heated up then you would have to be careful not to denature the catalase enzymes. Heating up the liquidised celery will cause the enzymes to move around more and increase the chance of it hitting a substrate molecule. The volume of hydrogen peroxide needs to be kept the same so that the number of substrate molecules is kept the same so as not to increase the chance of a collision between an enzyme and a substrate molecule.

    • Word count: 1828
  25. A Baker’s Problem

    Enzymes are biological catalysts produced in cells, made of protein. They have the ability to increase the rate of chemical reactions, although they are never destroyed nor altered during the reactions. Due to this aptitude, enzymes are extremely efficient, and are commonly described as being 'reaction specific'. By this, we can understand that enzymes only catalyse a specific reaction to make the product. The 'lock and key' hypothesis can be used to explain the method by which the glucose will react with the yeast enzymes.

    • Word count: 3390

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