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AS and A Level: Molecules & Cells

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  1. Investigating the break down of Hydrogen Peroxide using celery tissue to supply the enzyme - Catalase

    There are many factors that affect the speed of the collision between the enzyme and substrate. The higher the concentration of the substrate the greater the number of collisions, which take place with the enzymes. If there is a large number of substrates then there is a higher chance that they will collide with an enzyme and result in a successful reaction. With more successful reactions taking place, there will be a larger volume of product given off. Collision theory Collision theory is used to predict the rates of chemical reactions, particularly for gases. The collision theory is based on the assumption that for a reaction to occur it is necessary for the reacting atoms or molecules to come together or collide with one another.

    • Word count: 4499
  2. An experiment to test the effect of different temperatures on the permeability of cell membrane.

    A plant cell The dye would have no trouble passing through the cell wall by diffusion as it is fully permeable, but the tonoplast and the cell membrane are only partially permeable, and would only allow non polar substances to pass through. As anthocyanin is a polar substance, it cannot leave the cell by diffusion. Active transport is the next possible way for the dye to leak out, but this process requires energy, and so it is not likely to occur.

    • Word count: 3571
  3. The aim of this investigation is to investigate the enzyme activity by using Catalase and Hydrogen Peroxide. I will add Hydrogen Peroxide with Catalase and use a variable which will have an affect on the enzyme activity, so that it can be investigated.

    But as more and more enzymes are added, the reaction will soon become saturated therefore no matter how much more enzymes are added, it will not speed up the reaction any more. (As no more substrates are to be broken down into products) pH and enzymes Enzymes work best at a pH of seven (neutral). If the enzymes become too acidic or to alkaline, then they will denature or become inactive. Like for an example inside our stomach. When amylase is digesting the food in our mouths, and then we swallow it, the amylase becomes denatured by the pH scale of the stomach.

    • Word count: 3004
  4. Effects of Copper Sulphate on the Activity of Catalase

    Inhibitors that compete for the active site are called competitive inhibitors. a b Figure 3 The greater the concentration of substrate, therefore the more likely it is to occupy the active sites and the less likely the effect of the inhibitor. It is said to be competitive because of this reason. Non-competitive inhibitors (Fig 3b) tend to attach themselves to a sight other than the active site. In doing so, they alter the shape of the active site in such a way that the substrate is unable to occupy the enzyme.

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  5. The human body - Action and control

    They can be used over and over again. Digestive Enzymes are made inside cells but then are released into digestive system. They work outside of cells and are therefore called "Extra Cellular Enzymes". There are thousands of enzymes inside living organisms *37 degrees is the optimum (best) temperature for enzymes in a human. They work best then. *Graph-rates go up because of collision theory and then go down because the enzymes denature (destroyed by heat - change of shape) Enzymes usually stop working after 45 degrees. Enzymes are sensitive to pH, each enzyme works best at a particular or optimum pH *Enzymes can - build up lots of small molecules into a large molecule.

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  6. To Investigate the effect of changing temperature on the action of the enzyme catalyse, by measuring the volume of gas produced in 20 seconds

    The correlation of the points made it possible to draw a line of best fit onto my graph. By looking at the graph it is possible to find the optimum temperature for enzyme activity, by looking at where the line peaks. What I Have Found Out By looking at the graph you can see that the line of best fit shows a clear relationship between temperature and the rate of enzyme activity. At first, the rate of enzyme activity is increased, the higher the temperature. The rate of enzyme activity peaks somewhere between 37?c and 40?c although the lack of points makes this hard to be sure of, as we cannot really be certain about what is happening

    • Word count: 3629
  7. The Effect of Temperature on the Rate of Reaction of the Enzyme Catalayse and Hydrogen Peroxide

    Planning Due to a preliminary experiment I found an optimal temperature range of about 0-60�C because I realise that enzymes denature at about 50�C and beyond. This decision was also based upon our preliminary experiment. From my reading in 'Biology - a functional approach, (Nelson)' the following points can affect enzymes and so can be listed as possible variables; 1. The effect of temperature on enzyme activity. 2. The effect of pH or substrate on enzyme activity. I have chosen temperature as a variable.

    • Word count: 4112
  8. Locusts will be affected by temperature

    There are tubes (Bronchioles) along the side of the insects abdominal clearly visible with the naked eye, which is the passageway into the centre of the insect. These create a larger surface area that means the Insect can exchange gasses with the environment Easily. Also the Bronchioles are moist to assist diffusion since the Gasses are dissolvable in water easily so the chemicals then just travel through the liquid and the membrane, which is very thin. First of all I need a Locust and A Boiling tube to with hold the locust.

    • Word count: 3244
  9. The effect of osmosis on weighed potato chips

    Bellow is the animal cell: As you can see from this diagram, the animal and plant cell both have a cell membrane but the animal cell is different to the plant cell in other ways, which are all listed below: PLANT CELLS ANIMAL CELLS Have tough cellulose cell walls Do not have cellulose cell walls Have chloroplasts Do not have chloroplasts Have a large permanent Vacuole containing cell sap Sometimes have small vacuoles but they never contain cell sap Many have a box-like shape Shape varies Have a nucleus to the side of the cell Have a nucleus in the

    • Word count: 3190
  10. Investigate how concentration of the enzyme catalase in celery tissue alters the rate of reaction with hydrogen peroxide.

    and by otherintermolecular forces (Nuffield Advanced Chemistry, p.209). Secondary, tertiary and quaternary-structured protein molecules (haemoglobin is an example) are in increasing order of complexity. A tertiary-structured protein molecule is recognised by the supercoiling of the ?-helix (the secondary protein structure, an example is the DNA double helix). The three dimensional shape of the protein is stabilised by a "series of interactions between -R groups on the polypeptide chain". The '-R groups' are unspecified molecules which vary from protein to protein and are the 'active site' of an enzyme.

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  11. To what extent has genetic manipulation of the Calvin cycle forced the reappraisal of our understanding of the control of metabolic pathways in plants. What do studies of transgenic plants reveal about the integration of metabolism?

    carbamylation of rubisco). Longer-term "coarse" changes, such as those incurred during development, require the amounts of enzymes to be altered, through modification of the transcription of the gene or by protein turnover. Original thinking behind regulation of flux in a pathway has been that enzymes catalysing steps far from thermodynamic equilibrium (i.e. irreversible) are best suited for regulation as they provide a bottleneck for the pathway that relies on their catalytic abilities. Enzymes that catalyse steps that are at or near thermodynamic equilibrium (i.e.

    • Word count: 4193
  12. Factors that affects the rate of breakdown of a substrate by an enzyme

    I have chosen this over the other factors because firstly, temperature will be very difficult to control with the basic equipment used in schools. Therefore, without spending a large amount of money, in specially controlled environments, the results that I would obtain would be inconclusive or incorrect. I could use water baths set at different temperatures to conduct the experiment, but again, this would be inaccurate and ineffective. b) Secondly, pressure. For the same reasons, I am not investigating how pressure will affect the rate of catalysis.

    • Word count: 3746
  13. Investigating How the Concentration of the Enzyme Catalase in Celery Tissue Alters the Rate of Reaction with Hydrogen Peroxide.

    Like all globular proteins, enzymes possess hydrophilic R groups, the group which varies in different amino acids and determines their characteristics. H R GROUP O All amino acids (which join to form proteins) have a central carbon \ | // with an amine group (NH2) and a carboxylic acid group (COOH). N - C - C The only thing which differs is this R group and it thus determines / | \ the characteristics of the amino acids which make up the protein or H H OH enzyme.

    • Word count: 4520
  14. To investigate one of the factors that affects the permeability of cell membranes.

    The higher the temperature, the more the membrane will be damaged, and therefore the more the amount of pigment which leaks out. You can measure the permeability by seeing how dark the surrounding water is, or by measuring the amount of light which will transmit through. As the permeability increases and more pigment leaks out, the surrounding water will become a darker red, and the amount of light that will transmit through will decrease because there are more pigment molecules in the way.

    • Word count: 3743
  15. Amylase Investigation

    Enzymes are responsible here too; they control the absorption of radiant energy. Yeast use enzymes to levin bread and ferment sugar into alcohol. Bacteria use enzymes to break down cellulose fibre in the stomachs of cows and the stomachs of termites. Reproduction, growth, metabolism, synthesis, are all enzymes regulated reactions in living things. Enzymes are made from amino acids, and they are proteins. Because they are made up of proteins, they are sensitive to heat, pH and heavy metal ions.

    • Word count: 9104
  16. Investigating The Activity Of The Enzyme Lipase On Milk

    This is called the Lock and Key Hypothesis because the enzyme (lock) and substrate (key) only fit into their own match. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. However, if an enzyme meets an inappropriate heat or pH level, it is denatured which results in a crucial change in shape so that the key (substrate molecule) can no longer fit into the lock (denatured enzyme).

    • Word count: 3587
  17. Investigating the Effect of Glucose Concentration On the Rate of Reproduction of Yeast Cells

    In "http://esg-www.mit.edu:8001/cgi-bin/biosearch.pl?yeast", anaerobic respiration is called "http://esg-www.mit.edu:8001/cgi-bin/biosearch.pl?fermentation". These organisms are called facultative aerobes, because when oxygen is present, they respire aerobically, but if oxygen is absent, their respiration is purely anaerobic. In anaerobic respiration, as in aerobic respiration, the first step consists of breaking down glucose into pyruvic acid (see Box 1). However, the two processes differ considerably in the details of this step. In anaerobic respiration, there is no Krebs cycle. The end products of anaerobic respiration Box 1: Comparison between aerobic and anaerobic respiration (i)

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  18. An investigation into the effect of increasing the concentration of salt solutions on potato cells.

    This process is called Osmosis. It is the diffusion of water molecules from a place where they are in a higher concentration (such as dilute sugar solution), to a place where the water molecules are in low concentration (e.g. concentrated sugar solution) through a partially permeable membrane. Cell membranes are like visking tubing. They will let some substance pass through them, but not others, working as a partially permeable membrane. This diagram illustrates a plant cell in pure water. Plant cells do not burst in pure water.

    • Word count: 3413
  19. A Baker’s Problem

    Enzymes are biological catalysts produced in cells, made of protein. They have the ability to increase the rate of chemical reactions, although they are never destroyed nor altered during the reactions. Due to this aptitude, enzymes are extremely efficient, and are commonly described as being 'reaction specific'. By this, we can understand that enzymes only catalyse a specific reaction to make the product. The 'lock and key' hypothesis can be used to explain the method by which the glucose will react with the yeast enzymes.

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  20. Hydrogen peroxide (H2O2) an Enzymes Investigation

    Enzymes are used in solution, but many are immobilised to prevent losses. Enzymes are globular proteins, which catalyze metabolic reactions. Biochemical reactions in living organisms are essentially energy transfers. Often they occur together, "linked", in what are referred to as oxidation/reduction reactions. Enzymes allow many chemical reactions to occur within the homeostasis constraints of a living system. Enzymes function as organic catalysts. A catalyst is a chemical involved in, but not changed by, a chemical reaction. Many enzymes function by lowering the activation energy of reactions.

    • Word count: 4585
  21. Peroxide Investigation

    There comes a point however that the molecules are moving so fast that the enzyme becomes fractured and denatured when it collides with the substrate. Also if the temperature is too low there is virtually no molecular movement so no reaction is present. Therefore we could change the temperature in the experiment and record the oxygen production (hydrogen peroxide breakdown) at different specific temperatures. 3) Peroxide concentration - The more substrate molecules there are present in the solution, the more bonding will take place, assuming there are enough enzyme molecules to bond with them, as each substrate will bond with one of these enzyme molecules and so increase the reaction rate compared to when there were fewer substrate molecules.

    • Word count: 4206
  22. The effect of Electromagnetic Fields on Enzyme Activity

    These are produced by any object whose temperature is above absolute zero (-273 C ). Infra-red rays have many uses in our society, they are, in fact, utilized by fire-fighters to search for unconscious people, or by doctors to detect circulation problems and cancers. Lastly we encounter Radio waves which have the longest wavelength and the lower frequencies on the spectrum. Radio waves are the ones which interest us the most for this research. They are categorized in five groups: Microwaves, Ultra High Frequency waves, Very High Frequency waves, Medium waves and long waves. Microwaves have the highest frequency and are used in microwave ovens, for communication with satellites and for radars.

    • Word count: 9710
  23. Catalyse Investigation

    The more oxygen, the more catalyse activity and the less oxygen, the less catalyse activity. I will be able to measure the oxygen using the measuring cylinder. I will be using pureed potato to provide the enzymes for this experiment. This is the best kind of potato to use because it has more surface area than whole potatoes and this means more active sites for the substrate to react with.I will be change the enzyme concentration(amount of pureed potato) in order to measure its effects on the rate of catalyse activity. I will perform the experiment using 0cm3, 1cm3, 2cm3, 3cm3, 4cm3, 5cm3 of pureed potato.

    • Word count: 16451
  24. Investigating the permeability of plant cells.

    All membranes have this basic structure, which is shown in the diagram, Figure 1. Membranes are held together by very strong covalent bonds, as well as the large number of weak interactions resulting from properties of lipids and water which give the membrane its strength, and at the same time flexibility. In membranes the lipids are amphipathic, I.e., they have two sides to their nature. They are predominantly hydrophobic because of the tail part but have a hydrophilic head portion which is attracted to water. The head of the phoshpholipid is hydrophilic because its phosphate group and the terminal alcohol are charged and interact easily with water.

    • Word count: 5710
  25. 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.

    • Word count: 3230

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