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AS and A Level: Molecules & Cells

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  1. 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.

    • Word count: 1488
  2. 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)

    • Word count: 1336
  3. 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.

    • Word count: 1055
  4. 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

    • Word count: 1372
  5. 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
  6. 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
  7. This essay will look at different types of human tissues and will describe brief characteristics of four main types of tissue

    There are four basic or primary types of tissues (Figure 1.1). These are epithelial tissue, muscle tissue, connective tissue and nervous tissue (Layman 2003). All four types of tissue have special purposes, and therefore have varying different rates of cellular regeneration .For example bone tissue and adipose connective tissue are highly vascular and therefore heal quickly, unlike cartilage tissue is almost the slowest to heal (McGuiness, 2002). By basic or primary, it is meant that all of the specific types of tissues found in living things (especially humans and animals) are modification or specialisation of these four types of tissues (Layman, 2003).

    • Word count: 1512
  8. Describe how the Organelles in the Beta Cells Work Together to Produce and Secrete Insulin

    The messenger RNA is 'read' by the ribosome. Ribosomes are made of protein and RNA in 2 subunits and they have 2 tRNA binding sites. The mRNA passes between the subunits. It selects the complementary transfer RNA which carries the corresponding amino acid. Amino acids are joined in a chain to make the protein. The function of the protein is determined by the bonds formed from its primary structure (sequence of amino acids). Ribosomes are either free in the cytoplasm or are on the rough endoplasmic reticulum. Once the amino acid chain is formed it travels through the membrane tubes of the R.E.R..

    • Word count: 1625
  9. Describe the structural compartmentation of mammalian cells and the differing functions of these compartmentations

    There are several types of organelles in a cell. Some organelles such as the nucleus and Golgi apparatus are typically solitary, while others such as mitochondria and lysosomes can be numerous. The Quantity and structure of such organelles can vary between cell types. The Nucleus is the most prominent organelle. It contains the genetic material or DNA. In the form of genes, each with a host of helper molecules, DNA determines the cell?s identity, Controls the cell?s activities, and contains the coding information for the manufacture of proteins which are essential to survival.

    • Word count: 1063
  10. Immunity. The immune system is a group of cells and organs that defend the body against invaders causing disease

    There are 2 types of defence mechanisms, Non Specific and Specific. Non specific mechanisms don?t distinguish between one type of pathogen and another, but respond to all of them in the same way. They act immediately and take two forms, a physical barrier to the entry of pathogens and phagocytosis. The second defence mechanisms are specific mechanisms that distinguish between different pathogens; the responses are less rapid but provide long lasting immunity. The response involves a type of white blood cell called a lymphocyte which takes two forms, T lymphocyte (cell mediated response)

    • Word count: 1778
  11. The effect of concentration on catalase enzyme

    Controlled variables 1. Temperature ? the whole experiment will be carried out at room temperature in a lab. over a short time. This will reduce variation in temperature to a minimum. A thermometer will be left on the bench and temperature checked after each result is recorded to ensure that temperature did not change during the experiment. 2. Volume and concentration of hydrogen peroxide solution (substrate) will be kept the same for each disc (20cm3 of the 2 vol solution)

    • Word count: 1136
  12. Outline the structure of the main tissues of the body.

    They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes. Columnar cells: These cells are much taller with slightly oval nuclei. Columnar cells may have cilia or microvilli often specialised for secretion and absorption. Columnar cells are found lining the trachea and bronchi, villi in the small intestine. Ciliated cells they posses fine hair-like outgrowths, cilia on their free surfaces. These cilia are capable of rapid, rhythmic, wavelike beatings in a certain direction.

    • Word count: 1559
  13. The Cell Surface Membrane Research Essay.

    Proteins C. Carbohydrate D. Cholesterol E. Lipids The Phospholipid Bilayer The Plasma membrane consists of a bilayer of phospholipids. Its plays an important role because its structural components provide the barrier that marks the boundaries of a cell. Phospholipids are one of the major macromolecules in all living things and are essentially fats that are insoluble in water (Open University, 2002). There are two important regions of a lipid that provide the structure of the lipid bilayer; a hydrophilic phosphate head attached to two hydrophobic fatty acid tails (ibid). The head has a strong negative charge as a result of its internal phosphate group and the tail is composed of a string of carbons and hydrogens and has a slight kink in one of the tails due to the double-bond structure.

    • Word count: 1257
  14. Childhood Leukaemia

    The majority of children diagnosed with cancer are under the age of 5 years. All of the symptoms of leukaemia are quite general. All types of leukaemia have the same symptoms. These symptoms include: 1. Frequent persistent infections 2. Unusual bleeding and bruising 3. Tiredness 4. Paleness and 5. Breathlessness. However, because these symptoms are not specific and leukaemia is quite rare, doctors often don?t realise that the child is suffering from leukaemia at first. If leukaemia is suspected, a blood test is taken which will reveal low numbers of red blood cells and normal white blood cells and high numbers of defective white blood cells.

    • Word count: 1770
  15. Principals and Limitations of Electron Microscopy

    Transmission Electron Microscopes--------------------------------------------------------------------------------------------------- The Transmission Electron Microscope or TEM was invented over 70 years ago. These electron microscopes have a higher magnification as well as a better resolution than a light microscope which is limited to a resolution of 200nm whereas the TEM is about 0.1nm. The use of TEM have helped us to understand the structure and function of cells, tissues, organelles, microorganisms and molecules. TEMs work by using a tungsten filament to produce an electron beam in a vacuum chamber. The emitted electrons are accelerated through an electromagnetic field that also narrowly focuses the beam.

    • Word count: 1403

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