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AS and A Level: Molecules & Cells

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

    Investigate the effect of temperature on dehydrogenase activity in yeast. At which temperature is tetrazolium chloride (TTC) discoloured most rapidly?

    4 star(s)

    I will be observing the speed at which the colour changes with the redox indicator that I am using, tetrazolium chloride (TTC). This indicator is an artificial hydrogen acceptor; when oxidised is colourless, but when reduced it forms red, insoluble compounds called formazans. The compound ... NH2 - N=CH - N=NH ...Is called a formazans. Enzymes of the dehydrogenase class can be revealed I their location because they convert tetrazolium salts in solution to coloured, insoluble formazans. TTC can be used to show the presence of active dehydrogenase enzymes by a change in colour.

    • Word count: 2293
  2. Marked by a teacher

    Investigating the breakdown of hydrogen peroxide using celery tissue to supply the enzyme catalyst

    4 star(s)

    This can also be related to the collision theory. If the H202 is made more concentrated it means there are more particles of reactant between the water molecules, which makes collisions between the important particles more likely. This reaction is called a 'catabolic' reaction. This is a 'breaking down' reaction, where the enzyme combines with the substance for a short time, and then two substances are produced. Hydrogen peroxide is a chemical found in our liver, with the presence of enzymes in our body the catalyst help the decomposition of the H202 and accelerates it, so water and oxygen are produced faster.

    • Word count: 2343
  3. Marked by a teacher

    An investigation into the effect of Hydrogen Peroxide concentration on Yeast Catalyse activity

    4 star(s)

    The enzyme ends up unchanged by the process, ready to repeat it many times. Hypothesis Several ideas as to the likely outcome of the investigation can be drawn from this model of the enzymes working. Firstly, the reaction depends on H2O2 molecules actually coming into contact with the active sites of the enzyme. The chances of this occurring will be affected by the proportion of enzyme to substrate to water- both the stock H2O2 and yeast cells are supplied in aqueous solution, the H2O2 at a concentration of 32moldm-3 and the yeast at 2gdm-3.

    • Word count: 2328
  4. Marked by a teacher

    Vitamin C content of fruit juices

    3 star(s)

    This is because vitamin C is required in the synthesis of collagen which is an important protein in blood vessels, skin, tendons and ligaments. Vitamin C also plays an important role in the healing of wound and the repair and maintenance of cartilage, bones and teeth. Not only that, vitamin C is also a strong antioxidant. Antioxidants are nutrients that block some of the damage caused by free radicals, which are by-products that result when our bodies transform food into energy.

    • Word count: 2861
  5. Marked by a teacher

    An investigation to see how different sugars affect the growth and respiration of yeast.

    3 star(s)

    Prediction I predict that glucose will allow yeast to produce the most respiration. This is because it is a monosaccharide Fair Test Whilst doing the experiments, it is necessary to have minimal errors. By this, each experiment must be done fairly. To make each experiment fair it is important to make sure: * The same quantities are used throughout all the experiments. * Separate syringes are used for the methylene blue, sugars and yeast; this is to avoid any contaminations. * Repeat each experiment to gain an average set of results. * The same equipment must be used * The time be used in the same units throughout the experiments Safety It is important to ensure: * All equipment is used safely and correctly.

    • Word count: 2677
  6. Marked by a teacher

    Biology Coursework Investigation

    3 star(s)

    I found this out through the preliminary work. As the pH of an enzyme increases (becomes less acidic) the enzyme activity increases until there is an optimum pH. As pH increases further (becomes more alkaline) the activity decreases. At very low pH and very high pH, the enzyme is denatured and does not work. - The type of enzyme (input variable)- The type of enzyme you use is also very significant to your results. This is due to the fact that different types of enzymes have different optimum temperatures and therefore are denatured at different temperatures.

    • Word count: 2640
  7. Marked by a teacher

    Effect of different temperatures on the permeability of beetroot cell membrane.

    3 star(s)

    therefore there is a positive significant correlation between the two values. Group 2 Site Temp (�C) Rank R1 Absorbance (Arbitrary units) Rank R2 D (R1-R2) D2 1 25 1 0.26 2 -1 1 2 35 2 0.34 3 -1 1 3 45 3 0.21 1 2 4 4 55 4 0.63 4 0 0 5 65 5 2 6 -1 1 6 75 6 2 6 0 0 7 85 7 2 6 1 1 0 8 From using the formula the rs was 0.85, which is over the critical value (0.79)

    • Word count: 2077
  8. Marked by a teacher

    The effect of temperature on catalase activity

    3 star(s)

    For this reason few cells can tolerate temperatures higher than approximately 45�C. Enzymes are specific in the reactions they catalyse, much more so than inorganic Catalysts. Normally, a given enzyme will Catalyse only one reaction, or type of reaction. The enzyme has an active site that helps it to recognise its substrate in a very specific way. Just like a key only fits into a specific lock, each enzyme has its own specific lock; each enzyme has its own specific substrate. This is called the lock and key theory. The enzymes never actually get consumed in the process; they just increase the rate of reactions.

    • Word count: 2724
  9. Marked by a teacher

    Investigation of factors affecting the enzyme Amylase.

    3 star(s)

    Therefore I have developed two similar experiments (one for each factor I am investigating). To investigate the pH effects on the enzyme amylase activity. 1. Pour amylase solution into a test tube to a depth of 2cm. 2. Half fill another test tube with a 4% starch solution. 3. With a pipette, place a drop of iodine into each dimple in a dimple tray. 4. With a glass rod lift a drop of the starch solution from the first test tube and mix it with the first drop of iodine in the first dimple in the tray. A blue/black colour should develop; this will be used as the control. 5. Rinse the glass rod.

    • Word count: 2074
  10. 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
  11. 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
  12. 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
  13. 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
  14. Peer reviewed

    Compare the structures of a cell to those of a city. Although vast differences in size, organization and infrastructures seem alike, the cell and the city may share a lot in common.

    4 star(s)

    A denser region inside the nucleus is called the nucleolus which is the site of RNA and ribosomal synthesis. Surrounding the nucleus is a nuclear envelope which contains many pores allowing it to communicate with the cytosol by permitting the passage of large molecules. (5) Analytically, in a city the control centre is the city hall, where a Mayor works and along with the elected party runs the whole city, creating rules and legislation, administering public policies and regulating industries.

    • Word count: 2191
  15. Peer reviewed

    Transport across membranes How do substances cross into and out of cells.

    3 star(s)

    It is the cell membrane which ultimately defines the boundaries of all cells and protects it from environmental changes. The membrane provides numerous functions for a cell, they exhibit protective qualities as they control and prevent and regulate the passing of molecules within to and out of cells. The transport and exchange across cell membranes is an essential and continuous feature of the life of all cells. The intake of new materials and the expulsion of waste must all occur through the cell membrane. The cell membrane acts as a selective barrier between the inside of the cell and the external fluid/molecules.

    • Word count: 2313
  16. Peer reviewed

    Measuring Vitamin C content in different substances

    3 star(s)

    the juice), > Test tubes (To contain the solutions), > Stopwatch (To measure the time for the DCPIP to turn colourless), > Glass rod (To stir the contents of the test tube to ensure that it is distributed evenly), > Test tube rack (They are needed to hold the quantity of test tubes used to accommodate the solutions) Method: 1. Measure out 15cm� of Vitamin C solution and pour into a test tube. Measure out 1cm� of DCPIP, pour it into test tube with the Vitamin C solution and stir it evenly with the glass rod.

    • Word count: 2250
  17. Peer reviewed

    "An investigation to find out the optimum temperature for the activity of Lipase".

    3 star(s)

    I expect as the temperature is lowered the rate of reaction will be slower and that at the higher temperatures the rate of reaction will be decrease as the enzyme becomes denatured. * METHOD MATERIALS USED: Electric Kettle, 250ml Beaker, 10 Boiling tubes, 2 Boiling tube racks, Milk, Sodium Carbonate, Phenolphthalein, Spirit Thermometer, 5% Lipase. PROCEDURE: STEP 1: We mixed 5cm� of milk with 7cm� of Sodium Carbonate and added 6 drops of phenolphthalein into each of 5 boiling tubes.

    • Word count: 2210

    Firstly, what happens is that an adult somatic cell is taken from the body of a patient. Then the stem cell is inserted into an empty oocyte (egg cell) and a slight electronic shock is applied to initiate nuclear transfer between the two cells, which produce a zygote; this then ultimately become a mass of embryonic stem cells known as a blastocyst; the blastocyst has an inner and outer layer of cells. The inner cell mass are rich in stem cells and these stem cells are pluripotent, meaning that they have the potential to become any one of the 216 cells within the human body.

    • Word count: 2594
  19. How does the Primary Structure of a Protein dictate its overall Structure and Function?

    This peptide bond is formed, as can be seen on the diagram, between the amine group (NH2) and the carboxylic group (COOH) as a result of a condensation reaction. However, the actual structure and function of the protein is determined by other factors as well, namely the primary, secondary, tertiary and quaternary structures of protein which all in turn have a part to play in making the protein do its job efficiently and properly. Examples of the function of proteins are as enzymes, as cell signallers and structural proteins, to name but a few. By far the most well-known job of a protein is the role it has of the enzyme.

    • Word count: 2363
  20. Osmosis Coursework. Investigation to determine the water potential of apple tissue and carrot tissue, and how they compare to each other.

    Constant variables: * Mass, shape and size of plant tissues * Volume of sucrose solution (that each piece of plant tissue will be immersed in): 10cm3 * Immersion time of plant tissues: 40 minutes * Variety of plant tissues (by buying the apples/carrots from the same market, on the same day) Risk Assessment: * Glass test tubes/beakers must be handled with care, as they may shatter into sharp shards if glass which could easily cause an injury. Safety goggles and aprons should be worn to ensure protection and any broken glass should be disposed of properly - by using a dustpan and brush, then placing the broken glass into a designated glass bin.

    • Word count: 2133
  21. Free essay

    Alzheimer's Disease causes and treatments.

    Alzheimer's brain scans [4] Neurotransmitters are responsible for carrying messages within the brain. They are vital in controlling functions such as memory, speech and movement. Without an abundant supply of these, normal brain function will be very difficult to carry out. Another potential cause of Alzheimer's is the build-up of proteins and plaque between brain cells. As a person ages the concentrations of a protein called tau, and a protein called beta amyloid increase. These proteins cause fine fibres of protein to tangle together inside of a cell until the cell eventually bursts.

    • Word count: 2784
  22. Explain transcription and translation in protein synthesis.

    (Paraphrased: Barnett et al 2008 p40), the DNA molecule will have now uncoiled at that point. Once the DNA molecule at certain specific points have been separated into two strands the nitrogenous bases residing in the polynucleotide strands become exposed-vacant. This allows now for one exposed strand to act as a template allowing a complementary copy to be made. This copy another form of nucleic acid is called messenger RNA (mRNA). This is made up from free RNA nucleotides. Individual free RNA nucleotide will align themselves opposite one of the exposed 'template' strands and following base pairing rules they will

    • Word count: 2470
  23. Anatomy and physiology - cells, tissues and systems of the body. Describe the functions of the main cell components

    It contains proteins and acts as a temporary storage area. Smooth ER has no ribosomes attached to them and is involved in the metabolism of lipids. Golgi apparatus store proteins in it flattened fluid-filled sacs to transport to other organelles or upwards away from the cell as secretion. It is also responsible for the production of lysosomes. Ribosomes are not only jus attached to the outer layer of the rough ER, they can be found on outer surface of the nuclear envelope and throughout the whole inside of the cell.

    • Word count: 2226
  24. The Effect of Starch Solution on the Activity of Amylase

    I will prepare four different concentrations of amylase solution: undiluted, diluted to a half, diluted to a quarter and diluted to one tenth of the original concentration. The volumes of amylase solution and distilled water I will be using are on this table: Volume of amylase solution/cm� Volume of distilled water/cm� Final amylase solution 5.0 5.0 0.05 2.5 7.5 0.025 1.0 9.0 0.01 2. I will then need to set up a water bath at 35oC. 3. Then I will pipette 5cm� of undiluted amylase solution into one test tube and 5cm� of starch solution into another test tube.

    • Word count: 2420
  25. Free essay

    Can stem cell research provide a cure for diabetes?

    When the blood glucose level begins to fall (between meals, or when we have no food), the level of insulin falls. Some glycogen or fat is then broken down back into glucose and some is released back into the bloodstream to keep the blood glucose level normal. Hormones such as insulin are chemicals that are released into the bloodstream and have an action on certain parts of the body. Insulin is made by special cells called beta cells which are part of little 'islands' of cells (islets)

    • Word count: 2119

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