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AS and A Level: Molecules & Cells

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  1. Effect that the temperature has on the rate at which the Amylase (enzyme) can breakdown its starch (substrate)

    This is because the enzyme can not catalyse the reaction as the shape of the active site has become distorted therefore it can no longer combine with the substrate this is known as "lock and key " theory. I also predict that the more amylase (controlled variable) there is the quicker the reaction will take I know this because amylase catalyses the hydrolysis of starch. Preliminary Work Preparing the calibration curve experiment 1. Switch on the colorimeter to warm it up.

    • Word count: 1118
  2. An Experiment to Investigate the The Factors Affecting The Rate at Which Starch is Broken Down into Maltose.

    As soon as I mixed them I started the timer. After every 10 seconds I added 3 drops of the solution to 3 drops iodine in a well in a dropping tile. I counted how many wells I had used before the iodine had returned to its original colour I multiplied that number by 10 to find the number of seconds the amylase took to break down the starch into maltose. Table of results for preliminary work 1:1 ratio of starch to amylase 1:2 ratio of starch to amylase 1:2 ratio of amylase to starch Time in seconds 40 Before 10 seconds 150 Prelim conclusion The ratio of 1:2 starch to amylase was to quick to recorded therefore I could obviously not use ratio in my experiment.

    • Word count: 1905
  3. An investigation into the effect of temperature on the rate of reaction, on the enzyme Amylase.

    Proteases - digest proteins into amino acids. Digestive enzymes digest food by breaking down into chemicals, which are soluble. Food then passes through the gut wall into the bloodstream. A process known as absorption. Properties of enzymes: * They are all proteins * They are all catalysts * They all have active sites * Enzymes are denatured by high temperature. (40?c) * Enzymes work best at 37?c, (normally body temperature) * Enzyme work best at pH7. Except stomach enzymes. (pH2) * Enzymes are specific and only produce certain things. The specificity of enzymes. Enzymes have a specific shape that fits with their substrate, known as the "lock and key theory".

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  4. Effect of temperature on effectiveness on the Enzyme Pectinase

    It must be outlined that enzymes are specific: each enzyme usually catalyses only one reaction. It has been made clear that different enzymes can only catalyse different substrates, but this applies to the majority only. Some enzymes like amylase may catalyse grated apple, but only slightly. * Enzymes combine with their substrates to form temporary enzyme-substrate complexes. * Enzymes are sensitive to surrounding factors such as: temperature. Another fact about enzyme structure (enzyme-substrate structure) is that the Michaelis Constant (Km or Vmax/2)

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  5. To find the optimum temperature that the enzyme catalyse works at.

    The reaction that takes place creates gas and another liquid. Once I have timed the reaction at the vast variety of temperatures I can then establish at which temperature the enzyme catalase works best at. # The first part of the experiment involves cutting the pieces of liver to the same sizes so that there would be equal amounts of catalase in each. Each piece will be about 1.1 grams. That is the chosen weight that I have chosen since it is a reasonable mass. Then I will create 2 water baths, one for hot temperatures, and one for cold.

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  6. Investigating The Rate Of Enzyme Activity With Varying Enzyme Concentration.

    The first problem I came across was the matter of taking liver samples. It was far too difficult to accurately cut the liver, as it is too slippery. Instead I prepared a stock solution (I will detail this later) and reacted varying concentrations of the solution with hydrogen peroxide in a boiling tube and measured the frothy progress up the tube, I reacted 10ml of the stock solution with 5ml of hydrogen peroxide. After a few measurements it was clear that this was inaccurate as the results were so varied so I devised a new method of measuring the oxygen output.

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  7. Permeability of Cell Membrane in Beetroot Cells

    can be main factors affecting this. An excessive pH range (very acidic or very alkaline solution) could damage the ionic bonds in the proteins present in the membrane, therefore causing the shape of the protein to change preventing the membrane from functioning properly. Chemicals such as organic solvents e.g. ethanol, cause the membrane to dissolve effectively killing the cell as everything in the cell is released this is because the molecule is turned inside out therefore exposing the hydrophobic interactions which will readily dissolve in them.

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  8. To investigate the factors of the enzyme hydrogen peroxidase (catalase)

    The commonest secondary structure is a right-handed spiral shape, called an a-helix' Microsoft Encarta, 1997, describes proteins as 'any of a large number of organic compounds that make up living organisms and are essential to their functioning... Whether found in humans or in single celled bacteria, proteins are composed of units of about 20 different amino acids, which, in turn are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. In a protein molecule these acids form peptide bonds - bonds between amino and carboxyl (COOH)

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  9. How does an individual mammal distinguish its own cells and proteins from those of its invading enemies?

    Any material that can trigger the immune system into action is called an antigen. Antigens are foreign macromolecules not usually present in the body; they are the proteins, polysaccharides or glycoproteins that are on the surface of invading bacteria or viruses. Some of these invading pathogens produce harmful chemicals, called toxins. Toxins may also be antigens (http://www.bhs.berkeley.k12.ca.us/departments/Science/anatomy/anatomy97/immune/html/antibodygen.html). White blood cells (lymphocytes) play an important part in the immune response. Production of lymphocytes starts in the bone marrow. Once mature, the cells circulate through the blood and lymphatic vessels. Lymphocytes fall into two groups-the B cells and the T cells (Alberts et al 1983 p.952).

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  10. The Role of Proteins

    Also any other type of group ((r)) could join onto the central carbon in the molecule resulting in different types of amino acids. Due to the amino and carboxyl groups, amino acids are amphoteric which means that they have both acidic and basic properties. The amino group is alkaline and the carboxyl group is acidic therefore amino acids can act as good buffers in the human body. Buffers are essential in the body to keep conditions such as pH constant for efficient metabolic reactions.

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  11. Food Test. Aim: To conduct tests for reducing and non-reducing sugars, starch, lipids and proteins

    Also, in this experiment, the observations during each food test would be recorded and the colour changes would be observed to identify whether each food contain any of the macromolecules which are being tested. Materials/Apparatus: * Glucose solution * Sucrose solution * Starch solution * Iodine/ Potassium Iodide solution * Copper Sulphate solution * Sodium Hydrogen Carbonate solution * Ethanol (90%) * Potassium Hydroxide * Cold water * Vegetable oil * Egg albumen * Bread crumbs * Crushed potato * Test tubes * Test tube holders * Test tube rack * Measuring cylinder * Water bath * Pasteur pipette (dropper)

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  12. The effect of alcohol on the stability of cell membranes-plan for an experiment.

    If and when for any reason the tonoplast is damaged, the various parts of the vacuole will leak out into the surrounding environment. The sharpness of the red color within the environment must be similar to the amount of cellular damage of which the beetroot has gained. This experiment enables me to test the effect of three very different alcohols (methanol, ethanol, as well as 1-propanol) on cell membranes. These alcohols are found within alcoholic beverages of which are taken in social environment.

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  13. The lymphatic system during ill health

    * Lymph leaks out of the blood vessels * Accumulates in the spaces between the cells of body tissues. * Microorganisms are neutralised * Destroyed in the lymph nodes by white blood cells. * The lymph nodes are not swollen like how they do be whilst the body is fighting an infection * All sinuses are clear, however in the nose there is still mucus lining it to trap foreign particles from the air.

    • Word count: 414
  14. Classifying Microorganisms by Experiment

    On the other hand, due to the fact that gram negative bacteria have a strong outer membrane the crystal violet is not absorbed. Usually a counter stain - generally Safranin- is added to the slides after the crystal violet, all gram negative bacteria have a red or pink colour due to the Safranin. Also, according to the gram staining results along with the shape combination, the bacteria species could be identified. In this case, the observation we made was purple and long rod in appearance.

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  15. Report comparing different growth media, aseptic techniques and laboratory safety with own experiences

    Contact with broken glassware is prohibited and decontamination of sharp material before disposal is strictly required. Therefore, category 2 laboratories are required to provide special safety facilities and equipment such as the laminar flow cabinet which provides a sterile - particle-free- working environment with the help of air projecting through a system of filtration and carrying it across a working surface in a laminar air stream. There are three classes in biosafety cabinets, class I & II can be used in group 1,2 & 3 Microbiology Laboratories; whereas a class III cabinet will be used in a group 4 Microbiology Laboratory.

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  16. Protein Synthesis and Chemotaxis in Bacteria

    Here, the amino acid sequence is read and the guidelines are translated to form polypeptide chain (protein). Some modifications could occur in the Rough Endoplasmic Reticulum; these could be the addition of carbohydrates on to certain amino acids in protein. A few sugar groups could be attached to the chain of protein. This helps the folding process of protein to occur correctly and helps to stabilize the structure of it.

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  17. Organelles in animal cells and bacteria cells

    The layer of peptidoglycan in the cell wall differs from gram-positive bacteria (thick- multi layered) to gram-negative bacteria (thin- single layered). Capsule: Not all bacteria cells possess a capsule. It is an additional layer and surrounds the cell wall. Its functions are; shielding and protecting the cell when engulfed by another organism, aiding in the maintenance of the moisture of the cell, and helping the cell to bind to surfaces and nutrients. Mesosome: These structures are formed by the infolding?s of the plasma membrane in prokaryotic cells which perform aerobic cellular respiration and they are distinctive structures from eukaryotic cells. The enzymes linked with respiration are placed within these folding?s and they perform cellular respiration.

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  18. Isthe drug Levodopa the best option to fight Parkinson's disease?

    In Parkinson?s disease degeneration of the dopaminergic neurons producing dopamine means that lewy bodies form. This is when abnormal proteins develop inside nerve cells. The image on the right shows the difference of dopamine levels in a nerone between a healthy and Parkinson affected person. For an impulse to travel across synapses through the nervous system neurotransmitters are needed. They are released by vesicles and travel across the synapse to the receptors in the dendrite in an adjacent nerve cell where it recognises the neurotransmitter and continues the message by passing down the message in a similar way.

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  19. Cell Structure Revision Notes

    Their secondary cell wall is absent and they are lined with membrane. Plant cell organelles: Chloroplasts: * Enable plants to produce their own food * Large organelles- biconvex shape, 4-10mm long * Double membranes are present * Many internal membranes, some are arranged as stacks called grana * Loop of DNA found in the stroma Amyloplasts: * Double membrane present * Contains one type of starch called amylopectin * Amylopectin sometimes shows concentric rings Vacuole: * Surrounded by a single membrane called the tonoplast * Contains cell sap Plant stem structure and function: Epidermis: * Outer layer of the stem

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  20. Molecules and cells - Edexcel GCE Biology Revision Notes

    The rough ER is similar to sER but is covered in ribosome. They both contain a network of flattened, membrane-enclosed sacs / tubes known as cisternae. rER folds (folds the polypeptide chain into its 3D shape) and processes proteins. * Golgi apparatus is a group of fluid filled sac (consists of flattened membrane disks - cisternae) and vesicles are often seen at the end of the sacs. It processes and packages new lipids and proteins i.e. add carbohydrates to the protein chain to make glycoprotein. Lysosome is also produced here http://xarquon.jcu.cz/edu/uvod/04organels/043golgi/images/golgikomplex2.jpg * Centrioles are hollow cylinders containing a ring of microtubules (protein cylinders)

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  21. We are going to find out how different enzymes (in this case, trypsin) concentration in a solution would affect the rate of which solute (Casein) is broken down.

    This helps to explain why enzyme are so specific that they only catalyse one reaction. Rate of reaction of enzyme is directly linked to enzyme concentration, (given that the factors which affects enzyme activity remains constant at a point where trypsin is at active condition) as concentration of enzyme increases, so does the rate of reaction. This is due to the increased possibility of enzyme colliding with a substrate to form the enzyme-substrate complex (because there are more enzyme molecules present in a given value.). Independent variable in this investigation is the concentration of trypsin (2%, 1%, 0.5% and 0.25%)

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  22. Colorimetry Experiment - I will investigate and observe the amount of concentration of food dye in cherryade.

    The more concentrated the solution is, the more light will be absorbed, which can see be seen in the difference between the light at its origin and after it has passed through the solution. To get the concentration of an unknown sample, then several samples of the solution in which the concentration is known are first tested. These will be plotted on a graph such as scatter with the concentration at one axis and the absorbance on the other side to create a calibration curve.

    • Word count: 1929
  23. Experiment Aim: To investigate the effects of placing onion epidermal cells in different solutions.

    The slide was then labeled. The other piece of tissue was mounted in 1.0 moldm-3 sucrose solution and was examined using the light microscope. An objective was found which was appropriate for making measurements on the cell. This objective was used to measure the dimension A ( the maximum length of the cell) and B ( the maximum length of the plasmolysed cells immersed in 1.0 moldm-3 sucrose solution. The measurements were also made for five plasmolysed cell of the epidermis in 0.6 moldm-3 sucrose solution.

    • Word count: 633
  24. Influenza is a viral infection which attacks the respiratory system.

    Every year the World Health Organisation predicts the three strains of influenza virus that will affect people most and recommends that these are put in vaccines for that influenza season. For example The World Health Organisation (5) states that the vaccination last given out in the UK for the 2010-2011 season contained the; N1H1 strain (Swine flu), H3N2 strain and B strain. As explained in BBC Focus magazine (6) the vaccination works by containing a small amount of the influenza virus, shown in figure 1, containing the different strains recommended for that year.

    • Word count: 2445
  25. How the protein insulin is made.

    The cell membrane (fig. 1) is made up of various components, the main one being the phospholipid bilayer. Phospholipids are made up of fatty acid hydrophobic tails which are aligned in two layers to face inwards, leaving the hydrophilic heads to face the outward surfaces of the cell. This structure is described as the fluid mosaic model. Fig. 1 (www.tutorvista.com) This selectively permeable barrier is essential to the cells daily function as it allows substances in such as amino acids, oxygen and glucose.

    • Word count: 1090

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