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AS and A Level: Molecules & Cells

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  • Marked by Teachers essays 108
  • Peer Reviewed essays 26
  1. Marked by a teacher

    Analysing the vitamin C content in different fruit juices

    5 star(s)

    We get what we need, instead, from food. Besides, man is one of the few mammals unable to manufacture ascorbic acid in his liver. Excess vitamin C is eliminated through urine once the body has used up what it needs. Therefore, it is important to consume adequate quantities of fruits and vegetables containing vitamin C on a daily basis. Vitamin C plays important role in the body in many aspects, including : boosting the immune system, healing cuts and wounds, promoting healthy teeth and gums, protecting body against lifestyle diseases, improving eye?s health and enhancing the absorption of fundamental iron and zinc.

    • Word count: 3700
  2. Marked by a teacher

    Investigating respiration of maggots

    5 star(s)

    After several minutes I will close both the three-way tap and the screw-clip and make a note of the position of the manometer fluid. I will then begin the stopwatch and record how far the fluid has travelled after 1-minute time intervals. 9. Once I have carried out the experiment I will open the screw-clip and the three-way tap to allow the fluid to return back to normal. I will then repeat the experiment twice to allow for any anomalous results.

    • Word count: 5209
  3. Marked by a teacher

    Find out if enzymes work faster or slower at different temperatures.

    5 star(s)

    In the body enzymes are used in many ways. Enzymes are produced in the small intestine, pancreas, mouth, stomach and in white blood cells. In the stomach, small intestine, and mouth, the enzymes produced are to aid the digestion (breakdown) of food. The neutrase that we are using is also used in the digestive system being extracted from a bacterium (Baccilus Subtilis). There are two types of white blood cell, one type (the phagocyte) has a 3 - lobed nucleus and will engulf any bacteria in a vacuole and then release enzymes to effectively digest them inside the vacuole.

    • Word count: 5814
  4. Marked by a teacher

    Investigating the effect of enzyme concentration on the activity of cellulase.

    5 star(s)

    is plotted against enzyme concentration. Cellulose is found in wall paper paste and makes it viscous. The enzyme cellulase breaks down cellulose reducing the viscosity of the wall paper paste. This reduced viscosity can be measured by timing how long the paste solution takes to drain through a syringe barrel when different concentrations of the enzyme are added. From carrying out this experiment the result that would be expected would be as the concentration of enzyme increases the time taken for the wall paper paste to drain will decrease i.e.

    • Word count: 4527
  5. Marked by a teacher

    The Effect Of Temperature on the Respiration Of Yeast.

    5 star(s)

    Sexual reproduction of yeast only occurs in the yeast colonies occasionally. The genetic mixing that occurs in meiosis and the random fusion of haploid cells, results in genetic variation in the offspring. Respiration: - Yeast respires aerobically and anerobically. In this experiment the yeast is bubbled to make it oxygenated therefore the experiment will be aerobic for about 20 minutes before it will switch to anerobic respiration. Aerobic respiration: - C16H12O6 + 6O2 6CO2 + 6H2O Glucose + Oxygen Carbon + Water Dioxide Anerobic respiration: - C16H12O6 Alcohol + 6CO2 Glucose Carbon Dioxide Enzymes and TTC: - Enzymes have a big role in the anaerobic respiration of yeast.

    • Word count: 6179
  6. Marked by a teacher

    Beetroot Experiment. The purpose of this experiment is to determine the effect of temperature on the permeability of cell membranes

    4 star(s)

    Figure 2 shows the complex structure that is the plasma membrane. The image shows the arrangement of membrane proteins present within the phospholipid bilayer2 The plasma membrane is a complex and important structure whose major function is to determine which substances enter and leave the cell. Each protein channel will only let a specific molecule through, this is essential for controlling what goes in and out of the cell. Cytoplasm How would temperature affect the membrane? The purpose of the cell plasma membrane is to selectively control the movement of substances in and out of the cell.

    • Word count: 3524
  7. Marked by a teacher

    effect of concentration of copper sulphate on the action of amylase to break down starch.

    4 star(s)

    Copper sulphate Copper sulphate has the formula CuSO4 and is commonly used to control fungus diseases [17], both in agriculture and medicine. According to the Turkish Journal of Zoology (source 16), copper sulphate can inhibit the activity of amylase by 5%. Enzymes- Alpha Amylase Enzymes are biological catalyst, and a catalyst is substance which speeds ups a chemical reaction but remains unchanged itself at the end. [71] Enzymes are biological catalyst because they are globular protein molecules that are made by living cells to speed up reactions inside a living organism.

    • Word count: 8508
  8. Marked by a teacher

    The effects of Hydrogen Peroxide concentration on the activity of Potato Catalase

    4 star(s)

    Enzymes are long chains of amino acids, folded to produce a three-dimensional shape [2]. These folded chains of amino acids are specific to a certain enzyme. The structure of an enzyme can be described by four main structures. Primary structure A large number of Amino Acids join together (via peptide bonds) to form a polypeptide chain. From the 20 different kinds of amino acids available to link together, the primary structure is the number, type and sequence of these amino acids within the polypeptide chain sequence [1].

    • Word count: 4036
  9. Marked by a teacher

    Factors effecting enzyme activity

    4 star(s)

    Hydrogen peroxide is a by-product of fatty acid oxidation. White blood cells produce hydrogen peroxide to kill bacteria. Enzymes are used to speed up biochemical reactions by lowering the energy level necessary to initiate the reactions. Catalase's function is to catalyse the decomposition of hydrogen peroxide to water and oxygen. It is necessary to remove hydrogen peroxide, which is toxic, and a product of metabolism. The equation for this is, H202 --> H20 + O2 Balanced: 2H2O2 --> 2H2O + O2 But why do chemical reactions occur and why do rates of reactions differ? There is a simple answer to this, the collision theory.

    • Word count: 5094
  10. Marked by a teacher

    How does the concentration of enzymes affect the breakdown of starch by a-amylase in biological washing powders?

    4 star(s)

    This is the main reason why enzymes are used in washing powders. The enzyme I will be focusing on is ?-amylase, which is an enzyme present in biological washing powders that breaks down starch deposits in food stains into maltose, which is then further broken down into glucose sub-units. I however, am only looking at the initial breakdown of the starch by ?-amylase into maltose. Aim: The aim of my investigation is to investigate the effect that changing enzyme concentration has on the breakdown of starch (i.e.

    • Word count: 12799
  11. Marked by a teacher

    Investigate the effect of copper sulphate on pepsin activity.

    4 star(s)

    An enzyme works in a similar way, using what is called a 'lock and key' mechanism. This process is illustrated below. This 'lock and key' mechanism means that a particular enzyme will only catalyse a particular reaction, as different substrate molecules have different shapes and cannot all fit into one type of enzyme. This is why different enzymes are needed to catalyse different reactions. This is called enzyme specificity. Pepsin, like all other enzymes, is affected by temperature and pH. The general trend with enzymes and temperature is that the higher the temperature, the faster the enzymes can catalyse reactions, up until a certain temperature, where the rate of reactions begins to slow down, and eventually, when the temperature gets too high, the enzymes stop working.

    • Word count: 3300
  12. Marked by a teacher

    The effect of temperature on the enzyme Catalase.

    4 star(s)

    When heating the test tubes, measuring the froth or transporting the test tubes around I need to make sure that I don't shake or tip the test tubes to much as this could effect the froth produced. Method - For this experiment I will need some Catalase enzyme which can be found in potatoes. Also I will need some hydrogen peroxide (2H2O2). I will be using a ratio of 2:1 because I found that in my preliminary investigation this was best. 2 being Catalase and 1 hydrogen peroxide. So I will need 2ml of Catalase and 1ml of hydrogen peroxide.

    • Word count: 3769
  13. Marked by a teacher

    Investigating the effect of temperature on the movement of pigment through beetroot cell membranes.

    4 star(s)

    Preliminary Experiment: EQUIPMENT- * Beetroot:5 x 2mm discs/ sample * Beakers 400cm� * Distilled water * Thermometers * 10cm� syringe * 3 sample tubes and lids * Access to colorimeter BEETROOT PREPARATION- Cylinders of beetroot obtained with a No. 6 borer and cut into 2mm discs which are washed for several hours in running water to rinse away any pigment released when the cells were cut open during preparation. METHOD- 1. Heat 200cm� of distilled water to 75?C. 2. Whilst water is heating place 10 cm� of distilled water (at room temperature)

    • Word count: 4655
  14. Marked by a teacher

    The Effect of Substrate Concentration on Enzyme Action.

    4 star(s)

    To retard the decomposition of the peroxide into water and oxygen, organic substances, such as acetanilide, are added to the solutions, and they are kept in dark bottles at low temperature. The substrate that shall be used in this experiment is hydrogen peroxide. (2) Enzymes can be builders or breakers. Breakers are enzymes, which break down large molecules. Builders are enzymes, which build up large molecules from small ones. In a chemical reaction energy is required to break chemical bonds so that new bonds can be formed.

    • Word count: 3673
  15. Marked by a teacher

    Following the Progress of an Enzyme Controlled Reaction

    4 star(s)

    The Amylase is most efficient at an optimum rate at pH 7 in the mouth this is neutral. Amylase, any member of a class of enzymes that catalyze the hydrolysis (splitting of a compound by addition of a water molecule) of starch into smaller carbohydrate molecules such as maltose (a molecule composed of two glucose molecules). Two categories of Amylases, denoted alpha and beta, differ in the way they attack the bonds of the starch molecules. Alpha-Amylase is widespread among living organisms. In the digestive systems of humans and many other mammals, an alpha-Amylase called ptyalin is produced by the salivary glands, whereas the pancreas into the small intestine secretes pancreatic Amylase.

    • Word count: 4626
  16. Peer reviewed

    Effect of enzyme concentration on rate of reaction

    4 star(s)

    The shape of the active site is determined by the 3D structure of the enzyme as aforementioned. The 3D structure is dependant the bonds in the protein molecule that are affected by the enzyme's primary structure. Enzyme work by lowering the activation energy required for a certain reaction to take place. Activation energy is the minimum energy that must be supplied (usually in the form of heat) to chemicals before a reaction can take place. Image 1: Enzyme lowers the activation energy needed for a reaction to take place3 The basic mechanism of an enzyme is that the substrate molecules bind to the enzyme to form an enzyme-substrate complex.

    • Word count: 4053

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