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AS and A Level: Molecules & Cells

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  1. Marked by a teacher

    Discuss how the structure of cell organelles is related to their functions.

    3 star(s)

    There are two main functions of the nucleus. Firstly, it segregates all the DNA molecules from the cytoplasm. Secondly, the nuclear membranes administer as a boundary where cells control the movement of substances to and from the cytoplasm. The nucleus is made up from a few constituents. The nuclear envelope is a double-membrane system that has two lipid bilayers in which many protein molecules are firmly established. This prevents water-soluble substances to move without restriction into and out of a nucleus. The second component is nucleolus, which is a highly packed cluster of RNA and proteins, which construct to make subunits of ribosomes.

    • Word count: 1023
  2. Marked by a teacher

    Beetroot Experiment.

    3 star(s)

    In the cells of a beetroot plant, a substance called anthocyanin is contained within the plasma membrane. Anthocyanin, gives the beetroot its characteristic colour. If a cell is damaged in a beetroot plant and the membrane is broken, the anthocyanin 'bleeds' from the cells. It is this characteristic that can be subjected to test which conditions influence the cell membrane. We are experimenting with the effects of temperature on the membrane, so we will place the samples of beetroot into a water baths of varying temperatures and measure the colour change in the water.

    • Word count: 1040
  3. Marked by a teacher

    Effect of temperature on the enzyme pectinase in fruit juice production.

    3 star(s)

    At this point the enzyme is saturated and the reaction remains at the saturation level. 3. TEMPERATURE: More information on this particular factor is going to be presented a little later. Pectin is a molecule which has a structure similar to starch, the only difference is that the repeating unit of pectin is galacturonic acid instead of glucose as in starch. Galacturonic acid has a similar structure to glucose apart from the fact that one of the carbons has a carboxylic acid group (-COOH)

    • Word count: 3978
  4. Marked by a teacher

    An investigation into the inhibiting effect of tomato juice on the germination of cress seeds.

    3 star(s)

    If the inhibitors of the tomato juice are to inhibit germination there are various factors they can affect. For instance, the inhibitors can affect the enzyme amylase. Amylase is used to convert starch into glucose. The glucose is then used as a respiratory substrate to produce ATP. Without respiration the seed cannot germinate (because energy/ATP is needed for metabolisms for growth). So by inhibiting the enzyme amylase the inhibitors will prevent germination. The presence of inhibitors in tomatoes can provide benefits for the tomatoes.

    • Word count: 6218
  5. Marked by a teacher

    I am going to investigate the ability of Pepsin on Gelatin. I aim to investigate the effect of temperature on the rate of action of Pepsin on Gelatin.

    3 star(s)

    The volume of the pepsin was chosen to be 20ml. Variables * The volume of pepsin that is used * The amount of filmstrip that is used * Temperature of the pepsin * The concentration of the pepsin solution that is used * The apparatus that is used. * The method that is used. * Quality of film * pH of pepsin The variable will be temperature. This will be measured with a thermometer. The following non-variable parameters will be used (determined by preliminary work) - 20ml of pepsin 2cm by 2cm of filmstrip 2% solution of pepsin Black and white film The student has elected to perform the following

    • Word count: 2080
  6. Marked by a teacher

    How long does it take for the action of the enzyme 'amylase' (a type of carbohydrate) to break down the carbohydrate 'starch'?

    3 star(s)

    Factor to be investigated: The temperature factor will be investigated. This will indicate whether by increasing the temp, or decreasing the temp, will have any effect on the speed at which the starch is broken down by the enzyme. Prediction It is expected that as the temperature increases, starch molecules will be broken down more quickly. However, the temp may reach a point the enzyme de-natures, or stops working. This can be expected to be above 37.5�C. (At this temp enzymes and other biological materials may become damaged/ destroyed). The activation site may become wobble-like, and unusable, so stopping starch molecules from being broken up (see diagram).

    • Word count: 659
  7. Marked by a teacher

    Pectinase investigation.

    3 star(s)

    I believe this due to collision theory, this theory states that substances react together when their particles (atoms/molecules) collide with sufficient energy. These are called effective collisions. At higher temperatures the particles move faster because they have more energy therefore there are more effective collisions. When the reactants are more concentrated the particles are closer together and collisions are again more frequent. When substances react the products often have less energy than the reactants. Plan of Method 1. I will start off by setting up the equipment as shown below.

    • Word count: 1005
  8. Marked by a teacher

    How Does Temperature Affect the Action of Amylase on Starch?

    3 star(s)

    When the amylase is heated too much, it will stop the amylase molecules working because they will die. The optimum temperature for enzymes is about 37�C because this is body temperature, and this will produce the best results. Variables: * Temperature - The changed will be changed during this experiment. I will be changing the temperature at 5�C intervals starting at 20�C. * Time - The time taken to break to break the starch down according to the temperature will be recorded. Method: 1) The spotting tile will have the different temperatures of the amylase written on.

    • Word count: 591
  9. Marked by a teacher

    To investigate the effect of temperature on the enzyme catalase.

    3 star(s)

    7.Take the first conical flask containing the celery extract; arrange the apparatus as above and empty the syringe into the flask closing the 3-way tap start the stopwatch. 8.Measure the volume of oxygen released every 30 seconds for 2 minutes or until it is constant. 9.Repeat the experiment at 15, 35, 45 and 55�C. 10.Record the results in a suitable results table. Gas syringe (collect O2) Boss & Clamp 3-way tap Syringe (Contain catalase) Bung Clamp & boss Conical flask (Contain hydrogen peroxide)

    • Word count: 1317
  10. Marked by a teacher

    The Effect Of pH On Invertase Activity.

    3 star(s)

    Furthermore, there is a most favorable pH for enzyme - the point where the enzyme is most active. This point is known as the optimal pH. The aim of this experiment is to find out the range of pH which invertase is effective. Method This experiment was based on the premise that activity of invertase will be affected by different pH. Benedict solution was used as an indicator to determine whether the invertase had been denatured or not. If invertase was not denatured, glucose and fructose were produced. Benedict solution then would react with glucose and change its colour from blue to red.

    • Word count: 852
  11. Marked by a teacher

    To determine the effect of Detergent on the Permeability of Cell Membranes.

    3 star(s)

    They can be cationic or anionic. They exist in solution as the hydrophobic regions on the inside and hydrophilic regions on the outside make then soluble. They are able to penetrate lipids and make them soluble in water. The phospholipids in the cell membrane, as explained earlier also have long hydrophobic (non-polar) side chains and a polar (hydrophilic) head but they are arranged in a bilayer with the polar heads on the outside and the hydrophobic tails directed inwards. If a detergent comes into contact with the cell membrane, the non-polar, hydrophobic side chain of the detergent molecule penetrates and is taken up by the bi-layer of the cell membrane, and the polar head repels the individual phospholipids.

    • Word count: 3933
  12. Marked by a teacher

    To investigate the effect of Diastase on Starch

    3 star(s)

    Research in to Enzymes Enzymes are biological catalysts made up from protein that control vital biological processes. As we know catalysts are substances that speed up a rate of a reaction without itself being used up. An enzyme has an active site, which has a unique shape into which only a substrate of the exact same unique shape can fit. When this substrate fits into the active site it forms an enzyme-substrate complex. Enzymes can be denatured at certain conditions. These conditions are high temperatures and extreme levels of pH. The bonds that hold enzymes together are quite weak and so are easily broken by the above conditions.

    • Word count: 1325
  13. Marked by a teacher

    The effect of amylase concentration on the breakdown of starch

    3 star(s)

    Because the thing I am trying to test in the effect of the concentration of the enzyme, the only thing that I should be changing in each experiment is the concentration of the enzyme and nothing else. This will make all of the tests identical (apart from the enzymes concentration) which means the experiment should be accurate and fair. Because of this any differences in the results of my experiment I will be able to put down to the concentration of the enzyme.

    • Word count: 2298
  14. Marked by a teacher

    The Effect Of Temperature On Trypsin Enzymes

    3 star(s)

    The active site is an area on the surface of an enzyme where the substrate binds to and then the enzyme helps break up the substrate. An active site is for a specific substrate only and the shape of the active site is complimentary to the shape of the substrate. The diagram below should help explain this. Safety - Wear safety goggles because it could be dangerous if any substances were to make contact with your eyes. - Have something ready to wipe up any spillage's.

    • Word count: 1535
  15. Marked by a teacher

    Enzyme Investigation

    3 star(s)

    At first the rates increase, but when the enzymes begin to approach the maximum rate at which it can work (make the products), the effects of increasing substrate concentration goes away, because the enzymes are working at full pace and more substrate is useless. Biology Coursework Enzyme Concentration: Prediction: Reason - I predict that an increase in the concentration of urease will lead to a corresponding increase in the rate of reaction up to a point. For when there is enough enzymes to hold every molecule of substrate, an increase in enzyme concentration will have no effect.

    • Word count: 1319
  16. Marked by a teacher

    The Effect of pH on Pectinase

    3 star(s)

    Commercial pectinase may contain cellulase and other cell wall degraders. Pectin, which is found inside the apple puree I will be testing the pectinase on, can form gels that will bind up liquids. They do this by binding water. However they can only do this when the pectin molecules are very large, for example in fruits such as apples. In fruits pectin naturally functions as a type of 'glue' to help hold the cell wall together. The middle lamella in plant cells, which is between two cells, is densely packed with pectin, indicating that pectin helps hold cells together.

    • Word count: 3495
  17. Marked by a teacher

    Effect of Mouthwash on E-Coli Bacteria

    + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 24.23 = 130.77 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 39.07 = 115.93 Smaller Value = 115.93 Critical Value for U = 23 115.93 > 23 Comparison of Mouthwash A against C: U1 = ( n x n ) + (0.5n ) (n + 1) - ?

    • Word count: 1240
  18. Marked by a teacher

    Discuss the Biological Importance of Water

    Water is a very cleverly designed molecule. Hydrogen bonds can be formed with every atom in the molecule. Water is a polar molecule as the electrons are not held evenly. The oxygen atom is more electronegative so the electrons are held closer to the oxygen atom. This makes the oxygen atom ?- and the two hydrogen atoms ?+. Hydrogen bonds form between the oxygen and hydrogen atoms. This intermolecular bonding in the water molecule means it has a high boiling point and melting point.

    • Word count: 1039
  19. Marked by a teacher

    Beetroot practical

    * I left the beetroot pieces in a beaker of distilled water for one night. * Next day I placed the beetroot pieces into tubes of 5 cm of distilled water and placed them into different baths with different temperatures between 0-70. * After 30 minutes I collected 2cm3 fluid from each water baht. * The fluid in each of the test tubes was analysed using a colorimeter The variables kept constant * ?The same diameter corer is used so to keep the surface area of each beetroot piece the same size.

    • Word count: 769
  20. Marked by a teacher

    Enzyme concentrations using trypsin enzume and casein solution

    In five of the boiling tubes, different concentrations of trypsin are going to be used. By using a syringe measure out: - * 1st boiling tube - 10ml of trypsin by 0.0ml distilled water - 10% trypsin * 2nd boiling tube - 7.5ml of trypsin by 2.5ml distilled water - 75% trypsin * 3rd boiling tube - 5.0ml of trypsin by 5.0ml distilled water - 50% trypsin * 4th boiling tube - 2.5ml of trypsin by 2.5ml distilled water - 25% trypsin * 5th boiling tube - 0.0ml of trypsin by 10ml distilled water - 0.0% trypsin Label each boiling tube with the correct concentration.

    • Word count: 1769
  21. Marked by a teacher

    Discuss the proposition that plant and animal cells are fundamentally alike

    Animal and plant cells also contain cytoplasm. Cytoplasm is a clear jelly-like material that fills the volume of the cell. It is compiled of two parts: liquid cytosol, a concentrated aqueous gel that contain large and small molecules, and 'insoluble suspended particles', which include ribosomes. [1] The presence of ribosomes enable for protein synthesis to occur. The cytosol is the site for all chemical reactions that are required for the cell to exist. Apart from the nucleus, another important organelle present in a eukaryotic cell is mitochondria.

    • Word count: 824
  22. Marked by a teacher

    Aim: To estimate the solute potential of a plant tissue.

    Another factor that contributed to the errors in this investigation was that all of the data was approximated. Every single cell that appeared in the microscope was not accounted for and therefore all collected data is not exact, but instead a rough calculation. Another error that could have occurred, and that would explain what happened to the cells that were put in the solution with .4M, is that onion skin dried out before it was placed in the sucrose water.

    • Word count: 718
  23. Marked by a teacher

    Investigating the effect of temperature on the breakdown of starch by amylase.

    In this experiment, as the temperature increases, the enzyme and starch molecules collide more frequently (Brownian motion) and with more energy which will cause them to react more efficiently. At low temperatures, the molecules will not collide very frequently and the starch will not be broken down as quickly. It was predicted that the amylase would break down the starch most effectively at 40oC, and with decreasing efficiency towards 0oC, at which the amylase would be unable to break down the starch at all.

    • Word count: 2717
  24. Marked by a teacher

    Investigation of the Influence of a Variety of Treatments On the Permeability of Plasma Membrane.

    Charged molecules require ion channels for transport. Facilitated diffusion of a solute molecule uses a carrier protein by binding and causing a structural change in the protein such that the solute molecule can be discharged on the other side. Facilitated diffusion occurs down an electrochemical gradient and therefore requires no input of ATP unlike active transport which requires energy input in order to change the carrier protein's conformation and allow a solute molecule to be transported against a concentration gradient.

    • Word count: 1559
  25. Marked by a teacher

    Effect of temperature and inhibition on the rate of pepsin digestion.

    The enzyme pepsin, secreted by the chief cells in the stomach [2], is responsible for splitting proteins into peptides, or chains of fewer than 50 amino acids. However, many factors can affect the activity and rate of reaction of enzymes such as pepsin. pH, temperature, tile concentration of substrate, and the presence of inhibitors can alter the effectiveness of an enzyme [1]. It was already determined by Yang, et al, that pepsin requires the presence of HCl in order to adequately function [5].

    • Word count: 2107

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