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AS and A Level: Molecules & Cells

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  1. 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
  2. Lipids Analysis. Aim: To carry out a comparative analysis of the fat composition of two different types of milk,

    These test tubes were labeled. 5 drops of Sudan (iii) was added and the test tubes were then shaken. The tubes were filled with water (about ½ way), a cork was placed in each and then shaken vigorously several times. The contents were observed immediately after being shaken and after 10 minutes. Both observations were recorded and the necessary comparisons were then made. Precautions: To maintain the accuracy certain precaution are taken. The drops need to be at same depth in the solution so they travel the same distance. All apparatus should be cleaned before dealing with different solutions.

    • Word count: 835
  3. Is using stem cells to grow new eggs an effective alternative method of fertility treatment for infertile couples?

    Unfortunately this means the child will not biologically belong to one or both of the parents. Currently, a new method is being developed to try and give couples (who don?t have the necessary reproductive cells) the ability to produce a child that is genetically theirs using stem cells. Stem cell technology has the potential to offer an alternative to established methods of infertility treatment by growing new reproductive cells from the patient?s own tissues. This technology therefore offers couples in which one or both partners are sterile the ability to have child which is genetically their own.

    • Word count: 2310
  4. How organelles work together

    The rough ER has two functions which are to make membranes and to change proteins. Then the ribosomes? synthesising starts with the code AUG and then continues with 3 other nucleotides until it reaches the codons UAA, UGA and UAG. The codons tell the ribosomes to stop producing proteins as the protein is completed. When the polypeptide is made, it is sent to the rough ER where it folds into and 3D from amino acids. When the molecule is ready to be exported, the rough ER packages the molecule into a vesicle.

    • Word count: 578
  5. Modern solutions for Mesothelioma An Issue report

    Fig.1 A microscopic image showing asbestos fibres. On the other hand, the use of asbestos has been banned in the UK since 2006, however this does not stop the material from coming into the country, as people who may travel to the UK from another country which still uses asbestos, there is just the same amount of chance of someone getting Mesothelioma because of asbestos fibres still being in the UK atmosphere. Fig.2 shows a CXR scan of a Mesothelioma patient, from the image we can see that the bottom of the lung, the pleura (outer-lining of the lung)

    • Word count: 2806
  6. 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
  7. Vaccination and the components of the immune system

    From there the cell injects lysosomes into the phagosome. The lysosome then releases an array of digestion enzymes to destroy the phage. Finally the destroyed compounds in the phagosome are excreted out of the cell by means of exocytosis. -Describe how the specific immune system attacks pathogens The skin is thick and very hard to penetrate. In addition, the skin also produces a variety of substances that are harmful to invaders. Openings such as the eyes, nose, and mouth are protected by fluids or sticky mucus that captures harmful attackers.

    • Word count: 614
  8. Research project. Type 1 diabetes, is there a solution?

    Why is this problem? Diabetes is known to be the fifth most common cause of death in the world, and than one in ten (11.6 per cent) deaths among 20 to 79-year-olds in England can be due to diabetes, additionally reports from What is Diabetes type 1? Diabetes type 1 is an autoimmune disease (this is when the immune system is functioning abnormally normally against substances and tissues within the body). This takes place when Beta cells (which are known to metabolize and control blood sugar levels/glucose within the blood)

    • Word count: 3144
  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. Carcinogens may increase the risk of cancer by altering cellular metabolism or damaging DNA directly in cells,

    A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example gamma rays and alpha particles, which they emit. Common examples of carcinogens are inhaled asbestos, certain dioxins, and tobacco smoke. Although the public generally associates carcinogenicity with synthetic chemicals, it is equally likely to arise in both natural and synthetic substances. Cancer is a disease in which damaged cells do not undergo programmed cell death.

    • Word count: 682
  12. Antibiotics - Cure or Cause of infection?

    The main ways antibiotics work are: 1. Inhibition of bacterial cell wall synthesis ? a weak cell wall will lead to lysis of the cell. Penicillin is an example of an antibiotic which does this. The host is not affected because eukaryotic cells do not need cell walls. 2. Disruption of the cell membrane ? this causes changes in permeability of the cell and also leads to cell lysis. 3. Inhibition of nucleic acid synthesis, replication and transcription ? this prevents cell division and/or synthesis of enzymes and other proteins. 4. Inhibition of protein synthesis ? (e.g at ribosomes) Enzymes and other essential proteins are not produced.

    • Word count: 739
  13. The effect of temperature on beetroot membranes

    It would affect my results because a larger piece of beetroot would have more pigment in it, therefore more pigment could diffuse out after proteins embedded in the cell membrane have been denatured by heat, than in other pieces. This would mean a higher absorbency of light If my results were affected by incorrectly controlling this factor I would see inconsistencies in my results, and anomalies. Some would be higher than they are supposed to be when compared with repeats or other people?s data.

    • Word count: 753
  14. The Use of Water in Biological Organisms.

    Topic Four: Photosynthesis in plants, and how water is used to create energy through sunlight. The Use of Water in Biological Organisms Water is considered to be one of the most important biochemical molecules on Earth, forming the majority of all living organisms. Almost 75% of the Earth?s surface is covered in water; evolutionists believe water to be the catalyst for all life where evolution has taken place for over four billion years to create all the beings that exist today.

    • Word count: 810
  15. The effect of temperature on amylase enzyme

    Controlled variables 1. Volume of starch solution used for each temperature was constant at 5cm3 2. Starch concentration was 1% 3. Volume of amylase solution used for each temperature was kept constant at 1cm3 Hazards The main risk is irritation caused by exposure to iodine which could cause injury by entering the eye. The likelihood of this occurring can be reduced by wearing safety goggles. Other hazards are: 1. Risk of electrocution if water comes in contact with the electrical components of the thermostatic waterbaths 2. Irritation to skin or eyes if iodine solution is spilt on them 3. Allergic reaction to starch solution or enzyme. 4. Glassware breakage leading to cuts spectacles during the experiment.

    • Word count: 803
  16. 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
  17. Can Different Temperatures Affect the Cell Membrane of a Beetroot?

    The bilayer consists of phospholipids which arrange themselves so that the hydrophobic (?water hating?) tails are shielded from the surrounding water. The heads of the molecules are hydrophilic (?water loving?) and face the water. Overall, the cell membrane acts to selectively allow substances to move into and out of the cell and maintains the cell potential. Proteins within the membrane act as molecular signals allowing the cells to communicate with each other and other substances outside the cell. About 70% of the cell membrane is actually protein. The cytoplasm of the cell has a number of organelles, although there is one in particular that the vacuole.

    • Word count: 971
  18. 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
  19. The role of ATP in cells

    Most of the energy is stored in the bond of the last phosphate group and when energy is needed by cells, this bond is broken by a hydrolysis reaction catalysed by the ATPase enzyme. When one molecule of ATP is broken, adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) are produced as well as about 30KJ of energy which is released (this value is measured under laboratory conditions but it is estimated that in cellular conditions, about 50KJ will be released).

    • Word count: 479
  20. Compare and Contrast the structure and function of Prokaryote and Eukaryote cells

    To put it simply a Eukaryote is an organism whose cells contain complex structures enclosed within membranes and a Prokaryote is an organism where the genetic material is not membrane-bound, as you can see in the image below: Transmition Electron Microscope (TEM) image of Eukaryotic Cell Scanning Electron Microscope (SEM) image of Prokaryotic Cell However there are many more differences/defining features between the two, as you can see from the table below, there are many organelles absent and present in both which helps to show the difference between the two.

    • Word count: 645
  21. Types of tissue and their functions in the human body

    Therefore, the simple squamous epithelia help to determine what is able to move from the lumen and into the bloodstream the capillary bed is under the basement membrane, and vice versa. Stratified squamous: Stratified epithelium is also lining the tissue which provides protection for underlying tissues. Stratified epithelia are normally found in places where there is a great deal of wear and tear. Frequently, the outer surface of these epithelia is sloughed off and replaced by cells below it. Thus, the deeper layers of such epithelia are mitotically active.

    • Word count: 2280
  22. Diffusion of Iodine and Starch through the Semi-Permeable Membrane of a Visking Tubing.

    Bunsen Burner 2. Heatproof Mat 3. Tripod 4. Gauze 5. Beaker 6. Visking Tubing 7. Stirring Stick 8. 1g Starch 9. 200mls Water 10. 10 drops of Iodine 11. Pipette 12. Weighing Scales Methodology 1. Place Heatproof Mat on a flat surface and place Bunsen burner onto the mat, ensure the Bunsen burner is open so the flame is visible whilst lighting, close the Bunsen burner off so it becomes a blue flame and place Tripod and Gauze over the Bunsen burner. 2. Fill a beaker with 200mls of Water. 3. Weigh 1g of Starch and place into the beaker of Water 4.

    • Word count: 528
  23. How the body maintains an acid - base balance

    include bicarbonate and ammonia. A very common buffering system is the bicarbonate buffering system. It?s one of 3 major buffer systems in acid-base homeostasis. This is how it works: Carbon dioxide (CO2) combines with water (H2O) to form carbonic acid (H2CO3) which quickly splits into a hydrogen ion (H+) and a bicarbonate (HCO3-) . This can be shown in the equation below If there is a disturbance of the system, it will be compensated for by a shift in the chemical equilibrium. For example if here was a sudden rush of H+ ions into the blood and the bloods acidity was increased, the equation would work going to the left.

    • Word count: 890
  24. 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
  25. 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

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