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AS and A Level: Molecules & Cells

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  1. The effect of temperature on the structure of an enzyme

    Test tubes (4): These will be used to place the amylase and starch solution in 2) Test tube rack: This will be used to place the test tubes into 3) Graduated pipettes (2): These will be used to measure the amount of Amylase/starch solution needed. 4) Glass rods (2): These will be used to place the mixture of the amylase and starch solution into the spotting tiles. 5) Water baths maintained at 100C, 200C, 300C, 400C, 500C and 600C (6): These will be used to heat up the solutions. 6) Thermometers (2): These will be used to tale the temperature reading of the solutions.

    • Word count: 1625
  2. Transport Across Plasma Membrane

    Finally, those that are on the inside surface maintains the cell's shape and motility, such as enzymes. Glycoprotiens and glycolipds are found on the surface of the cell. They form a cell coat (glycocalyx) and are important in cell protection and recognition. The bilayer is described as fluid since the lipids within it are able to slide around and exchange places with each other freely. This feature allows processes such as phagocytosis to occur. There are five main ways in which transport across cells can occur: Simple Diffusion; The only substances that can diffuse directly through the membrane are either those that are lipid soluble or those that are very small.

    • Word count: 1093

    Unlike ordinary catalysts, they are specific to one chemical reaction an ordinary catalyst may be used for several different chemical reactions, but an enzyme only works for one specific reaction Amino acids are the basic building blocks of proteins. Basically, amino acids are joined together by peptide bonds to form the basic structure of proteins. However, owing to the many 'side groups' that are part of the amino acids other sorts of bonds may form between the amino acid units.

    • Word count: 1698
  4. The Application of Enzymes In Medicine

    "are enzymes that cut DNA at specific sites," which "cut bonds in the middle of the polynucleotide chain," (2). The DNA is then modified including "degradation, synthesis, and alteration of DNA," (3, pg. 42). DNA ligase is another enzyme used and is the opposite of endonucleases. Whereas endonucleases are used to cut DNA, DNA ligase "is used to seal discontinuities in the sugar phosphate chains..." (3, pg. 44). Endonucleases are also used for genetic fingerprinting, (4, pg. 77). Enzymes are also used in analytical tests for example to test for "glucose, urea, ketones, cholesterol etc. in blood and urine," (4, pg.

    • Word count: 1132
  5. How does the Rate of a Reaction involving Amylase differ as the Temperature changes?

    We have chosen to vary the temperature, there are three other variables to change and see what effect they will have on an enzyme, therefore all other variables need to be controlled. We will need to control the pH because the pH scale represents the percentage of hydrogen ions in the solution; these H+ will react with globular protein and make hydrogen bonds with its side chains. Therefore each molecule has its own pH it works best at. At the optimum pH the active site of an enzyme will accept the substrate.

    • Word count: 1311
  6. What are 'Enzymes'?

    Since it is poisonous, the cells must either get rid of it or change it to something nonpoisonous. If they cannot do this, the cell may die; catalase solves this problem. The enzyme catalase is found in animal and plant tissues, and is especially abundant in plant storage organs such as potato tubers, corns, and fleshy part of fruits. Catalase reacts with the H2O2 to form water and oxygen: 2H2O2 + Catalase � 2H2O + O2 + Catalase What is Catalase? Enzymes are very large and complex organic molecules that are synthesized by the cell to perform very specific functions.

    • Word count: 1317
  7. Investigation into the Effect of Temperature on the rate of Respiration of Yeast

    A delivery tube with a bung was then placed into the test tube of yeast, with the bung end of the tube going into the test tube of yeast. 5. A second test tube was then filled with water and placed in a test tube rack. 6. The other end of the delivery tube was then placed into this second test tube. 7. The number of bubbles coming out of the delivery tube into the second tube per minute was then measured.

    • Word count: 1617
  8. How to measure the rate of a chemical reaction catalysed by an enzyme and then how I can change the rate at which the enzyme speeds up the chemical reaction.

    This makes collisions between important particles more likely to happen. In gas, increasing the pressure means the molecules are more compressed, so there will be more collisions. Surface area If a reactant is a solid it will have a relatively small surface area. Breaking it down into small pieces will increase the surface area, so more of the surface is exposed in the solution. There is more area to work on, and more useful collisions will happen. The factor I have chosen to investigate that will affect the rate at which the enzyme changes the rate of the reaction is concentration.

    • Word count: 1853
  9. Aim: Toinvestigate whether immobilised enzymes are less susceptible to denaturisationthan non-immobilised enzymes by measuring the time taken at differenttemperatures for the enzyme to denature.

    The quaternary structure is when two or more proteins bond together forming a biologically active molecule. The active site is able to lower the activation energy (energy needed for a reaction to take place) by placing reactants in a closer proximity, correctly aligning them thus making a reaction more likely. There are different factors affecting the activity of enzymes: Temperature This can be explained by the kinetic theory. In that as the temperature increases, the molecules vibrate faster due to the increase in energy. Therefore the number of collisions increases. However if the enzyme has reached its optimum temperature and the temperature continues to increase, the enzyme molecule starts to loose its shape, particularly the tertiary structure.

    • Word count: 1212
  10. To investigate the effects oftemperature on catalyse action?

    -Hydrogen Peroxide- 15ml -Tile -Kettle. This would be used to boil water for 80�c, in experiment. -Potato- 3 grams -Borer -Water Bath -Scales -Ice cubes- 0�c of water in experiment -Knife Method I will carry out my experiment by following these stages: -I will collect and set up apparatus as shown above -Use the borer, then cut the potato into smaller pieces. - Weigh 3 grams of this -Collect 15ml of hydrogen peroxide -Set up as shown in apparatus -Time the experiment for one minute -When time has reached measure the amount of water left in the measuring cylinder -Do this for each temperature.

    • Word count: 1492
  11. The dna structure and function compared to the rna.

    Immobilised glucose isomerase is used for the preparation of high fructose syrups from starches. Fructose is a sugar found in fruits, however, it is sweeter than other sugars like glucose and sucrose, and it contains fewer calories. Fructose is obtained from starch; therefore using the enzyme amylase starch is converted to glucose. The glucose is then converted to fructose using the enzyme glucose isomerase. This particular enzyme is used in the immobilised form because it is relatively expensive to produce, therefore it is easier to recover the enzyme and reuse them.

    • Word count: 1211
  12. The costs of cigarette smoking

    Nicotine addiction is only part of the problem of tobacco use. Analysis of smoke from burning tobacco reveals over 4000 separate compounds, including DDT, arsenic and nitro amines. One of the most damaging compounds in tobacco smoke is the poisonous gas carbon monoxide - the culprit when someone dies from fumes of a running car engine in a closed garage, witch shoes just how deadly it is. What do the free radicals, nicotine, and other tobacco compounds actually do to human cells?

    • Word count: 1503
  13. Structure and Function of Red Blood Cells and White Blood Cells

    Without a nucleus RBC's can never divide. Lacking in organelles, they can only survive for about 120 days, before being 'eaten' by white cells. Some 3 million RBC's die and are scavenged by the liver every second. Structure RBC's are biconcave shaped discs (as seen in this electron micrograph), about 7.5�m diameter. The shape gives an increased surface area, allowing the cell to contain more haemoglobin. The small size and large surface area both increase the rate of diffusion of O2 and CO2.

    • Word count: 1044
  14. Stem cells

    'It wasn't until very recently that sources of cells that might be used to regenerate other organs became available'. (James Thomson, University of Wisconsin, USA). Main body Human life is created when an egg is fertilised by a sperm, when joined the two 'gametes' create a single cell organism that eventually develops into a baby. The fertilised egg is said to be 'totipotent' meaning that its potential is total. The single cell splits within hours of fertilisation, forming two identical totipotent cells.

    • Word count: 1151
  15. Rate of catalase activity.

    I think at first the reaction will be rapid but as time goes on the reaction will slow down. This is because the hydrogen peroxide will start to be used up and there will be less hydrogen particles to collide and therefore less oxygen will be produced. I think that at body temperature (370C) the reaction will take place the fastest as the enzyme is working at the temperature it normally works at. At very high and low temperatures the reaction will not occur. 2M Hydrogen Peroxide Solution Liver (1.3 grams) Tap Water Test tube Bung Container Measuring cylinder Stop clock.

    • Word count: 1296
  16. An essay on the structure of a typical human cell.

    The nucleus has structures within it, nucleolus, genetic material (chromosomes and DNA) and heterochromatin which are the dark stained area. The nucleus is surrounded by a nuclear envelope; this has two membranes, an inner membrane and an out outer membrane and is about 10 micro meters. The nuclear envelope has nuclear pores in it which let genetic information go in and out. In addition, the nucleolus of the nucleus produces the RNA that is used to make ribosomes. Linked to the nucleus is the rough endoplasmic reticulum, which consists of compartments and these compartments are called cisternae.

    • Word count: 1095
  17. Regulation of Glycolysis.

    This is important in order to avoid wasting the energy we take in as food. ATP is not a long term energy store, so if we do not require immediate energy, it is more beneficial to store the glucose as something else such as glycogen rather than metabolise it immediately. The pyruvate created in the reaction can also be used to synthesise biological molecules, hence the abundance of these molecules in the cell also has an effect on the rate of glycolysis. In most metabolic pathways, the reactions are controlled by enzymes that catalyse non-reversible reactions.

    • Word count: 1342
  18. What can the study of after effects tell us about how the brain processes visual information?

    Different neurones may correspond to different spatial frequencies. Frequency coding is when different values on a sensory dimension may be represented by the frequency of nerve impulses in a single nerve. Bekesy (1929; as cited in Mollon, 1974) argued stimulus coded by place would show a distance paradox; that is the maximum after effect will be for stimulus some distance along the direction from the adapting stimulus. If an after effect shows distance paradox then that sensory dimension is probably coded by place. If it is coded by frequency then adaptation at any part will reduce sensitivity at all points along the dimension (Mollon, 1974).

    • Word count: 1868
  19. Use of Enzymes in Industry and Medicine

    Also bleaching is made easier by an enzyme called hemicellulase instead of using chlorine which cuts down the cost of using vast amounts of chlorine be a third and also less harm is done to environment, The advantages of using enzymes in the paper industry is that they can produce quality paper faster, also a lot less energy is needed because the enzymes require less energy. There are no disadvantages for using enzymes in paper industry. Starch Industry The starch processing industry is the second largest segment of the industrial enzyme market.

    • Word count: 1842
  20. Explain why the structure and function of proteins is essential to living organisms.

    The four levels are: Primary, Secondary, Tertiary and Quaternary. Primary structure makes up the most simple proteins, These fibrous proteins are made up of simple polymers of amino acids and are generally very long. They consist a polypeptide backbone running down the peptide bonds with the variable groups jutting out to the sides, as demonstrated in the diagram below. Secondary structure is slightly more complex than Primary. This refers to the way the polypeptide chains are twisted and folded due to hydrogen bonding. Within Secondary structure there are two types of bonding: Alpha Helix and Beta pleating.

    • Word count: 1325
  21. Nervous System

    This can result in us not being able to control our body, as well as we should. How Nerve Cells Communicate Each microscopic nerve cell, or neuron, has a blob shaped main part, the cell body, with thin, spider-like dendrites and one much longer, wire-like nerve fibre or axon. The axon's branched ends have button shaped axon bulbs, which almost touch other nerve cells, at junctions called synapses. Nerve signals travel along the axon and 'jump' across synapses to other nerves cells, at speeds of more than 100 metres per second. Although a neurone is specialised to transmit electrical impulses it has many features in common with the generalised cell.

    • Word count: 1646
  22. Investigate how varying PH affects the activity of the peroxidase enzyme.

    But the enzymes can be useless when they are denatured this happens when their active site is changed around the 40-50�c. PH can also cause denature of the enzymes, most work at neutral PH, So extreme acidic or alkaline PH will denature them, a good example of this reaction is Peroxidase. When this happens they become useless to the body. There are a lot of certain enzymes for the right job, as you will see in the prediction section. There is three parts the enzyme and a part a and b they join together at the active site the molecules of substances combine with the enzyme for a short time.

    • Word count: 1030
  23. The effect of temperature on the cell membranes of beetroot cells and amount of pigment released.

    * The beetroot piece is then placed into a tube of 5 cm of distilled water. This procedure will be repeated with the other four pieces of beetroot and the temperature should be changed accordingly. The temperatures will be using are 20oC, 40oC , 60oC and 80oC Each time a piece of beetroot is removed from the heated water, it will be left in the distilled water for exactly 30 minutes, before being discarded. The fluid in each of the test tubes will be analysed using a colorimeter and compared against the control, which is distilled water to check for any variations in the colour of the water.

    • Word count: 1209
  24. Phagocytosis and the Immune Response

    This human macrophage like its cousin the neutrophil is a professional "phagocyte" or eating cell (phago = "eating", cyte = "cell"). But eating the organisms is not enough. To insure that the organisms not grow and divide within the macrophage, the white cell must kill the organisms by some means such as the oxidative burst. This process is shown in the diagram below. Reference: John Adds - 1999 - Respiration and coordination Macrophages, which are similar to the monocytes, are also derived from the stem cells in the bone marrow. These cells are present in the liver, spleen and lungs.

    • Word count: 1307
  25. The effect of substrate concentration on the rate of decomposition of Hydrogen Peroxide when catalysed by the enzyme Catalase.

    It works very quickly to reduce levels of Hydrogen Peroxide when present. It catalyses the decomposition of Hydrogen Peroxide by liberating Oxygen gas as effervescence. Catalase is also one of the fasting working known enzymes; each enzyme can produce 1012 molecules of oxygen per second by the decomposition of 40,000 Hydrogen Peroxide molecules per second at only 0 degrees Celsius. The enzyme-substrate complex is the stage where the enzyme has joined with the substrate ready for the reaction to take place. The substrate must be of a particular size and shape to fit into the enzymes active site, once it has, the complex only lasts for a matter of seconds, and the products are formed.

    • Word count: 1806

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