Chiral Drugs What is chirality? Chirality is the property possessed by a molecule with such spatial arrangement of atoms that it cannot superimpose on its mirror image.

Chiral Drugs What is chirality? "Chirality" is the property possessed by a molecule with such spatial arrangement of atoms that it cannot superimpose on its mirror image. The object and mirror- image pair of molecules has the same constituents and structural formula. Their relationship with each other is similar to our left and right hands. The carbon atom of a simple chiral centre has four different groups arranged tetrahedrally (Fig. 1). Isomers of such nature are called enantiomers. Fig.1: A chiral molecule with tetrahedral arrangement and its mirror image. There are three types of stereoisomers, namely enantiomers, diastereomers and geometrical isomers. . Enantiomers are two stereoisomers containing asymmetric carbon atoms related as non-superimposable object and mirror images. If an enantiomer rotates polarized light to the right or in a clockwise direction, it is said to be the (+) or the dextrorotatory isomer. On the other hand, if the plane polarized light is rotated to the left or in a counter-clockwise direction, the isomer is called as the (-) or the levorotatory isomer. Enantiomers are identical in chemical and physical properties except for the direction of rotation of plane polarized light. 2. Diastereomers are stereoisomers that are not related as object and mirror images. They contain at least two asymmetric carbon atoms. Unlike enantiomers, the

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Cellular Structure and Function

Cellular Structure and Function Introduction Cells are organised together into functioning groups called tissues. These groups of cells organise together to perform a specialised task. There are four basic types of tissues found in the human body; these are epithelial, connective, muscular, and nervous. The following text aims to explain the structure and function of these tissues as well as ovum and sperm cells. Epithelial Tissue Epithelial tissues, as with all different types of tissue, can be found all over the body, they generally line the inside or outside of a body cavity. The cells are anchored down by basement membranes and form in different shapes such a flat, cuboidal, and columnar. The below text details several different types of epithelium cells that can be located around the body. . Stratified Squamous Epithelium Stratified squamous epithelium cells are present in areas of the body that are very moist and subject to abrasion, such as the mouth, esophagus and vagina. The cells are packed densely together and are very flat and irregular in shape. The tissue functions to provide a barrier to entry to inside the body and protects underlying tissues from friction and drying. Figure A. above shows a drawing of the epithelia from an overhead point of view, in shape they are very similar to that of a fried egg. Figure B. shows the cells from a side-on point of

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effect of temperature on the rate of respiration in yeast

Effect of temperature on the rate of respiration in yeast Aim: My aim is to investigate the effect of temperature on the rate of respiration in yeast by using a universal indicator. Background theory: Enzyme: Enzymes are organic catalysts that speed up the rate of a chemical reaction without being permanently altered in the process. Enzyme Characteristics * Lower the energy of activation * Form reversible complex with substrate. * Not consumed in the reaction therefore they are effect in small amounts * Very specific - (Induced fit hypothesis) react with only a single substrate. * Many need cofactors, such as certain vitamins, to be activated. * 2000+ enzymes per cell, different cells have different enzymes. * Enzymes are produced by genes. * Genetic disorders are the result of faulty enzymes. * Operate best in optimum conditions of pH, temperature, etc. * Are controlled by feedback mechanisms. Enzyme mechanism: Key and theory: The substrates (reactants) are attracted to the enzyme molecule. They join forming an enzyme-substrate complex. The reaction occurs on an area of the enzyme molecule known as the active site producing new substrates(s) or products. Induced fit hypothesis: The attraction of the substrate and enzyme form an enzyme-substrate complex. It was originally referred to as the Lock and Key Enzyme Theory. The current theory

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The Synthesis Of Phenacetin From p-Acetamidophenol

CH1751B - EXPERIMENT 15 The Synthesis Of Phenacetin From p-Acetamidophenol Introduction: "Phenacetin is an analgetic and an antipyretic reagent which acts in the body by temporaririly inhibiting prostaglandin synthesis in the central nervous system". Aim: * To synthesise Phenacetin from p-Acetamidophenol and purify it by recrystallisation. * Analyse purity of Phenacetin produced, by comparing the melting point with the literature values, the appearance and the Infrared Spectrum. Method: Sodium metal (0.6g, cut into small pieces) was cautiously placed into a dry 100cm3 round flask by taking the flask to the "sodium" balance and placing the sodium directly into the flask. A dry reflux condenser was attached and industrial methylated spirits (IMS, 15cm3) was added. A vigorous reaction occurred for 5-10 minutes under reflux until most of the sodium had dissolved. Once the solution had cooled 3.8g of p-acetamidophenol was added. Through the top of the condenser ethyl iodide (3.0cm3) was introduced to the pale green mixture and the mixture boiled at reflux temperature (20-25°). Ethyl iodide was obtained from a burette in the fume hood few minutes before its use, due to its flammable nature and harmful vapour. A darkening green colouration occurred while p-acetanilide dissolved changing through to brown and then yellow. Once the reflux was completed 40cm3 of water was

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chemistry OCR-open book 2008

Section1: Discuss with the use of examples the main difference between Alpha decay and Beta decay: An alpha particle consists of 2 protons and 2 neutrons (He- nucleus), which is emitted as the nucleus looses 2 protons and 2 neutrons to become more stable. In this process a new chemical element is produced and this process is called transmutation, and this is a spontaneous reaction. For example the decay of Uranium-238 into Thorium- 234 E.g. 1 Beta decay: A beta- particle is a high energy electron, emitted when a neutron in the nucleus decay to form a proton and an electron. E.g. 1 E.g. 2 The differences between alpha and beta decay: Alpha decay Beta decay It's a form a nuclear fission reaction, where the atom splits in to two daughter nuclei. An energetic negative electron is emitted, producing a daughter nucleus of one higher atomic number and the same mass number. Alpha decay is restricted to heavier elements; an element only emits an alpha particle is it atomic number is less than 82. Beta particle is emitted when a heavy element decays with atomic number of above 82 decays. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus. A beta particle is emitted when there is too many neutrons, a neutron decays into a proton, an electron and an antineutrino. Difference between nuclear fission reaction and

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Effect of Anaerobic Respiration On Yeast

The Effect of Temperature on the Anaerobic Respiration of Yeast Aim: To investigate the effect of temperature on the rate of respiration in a suspension of yeast Saccharomyces cerevisiae. Background Knowledge: Yeasts are a form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species known. They reproduce asexually by budding mainly, although some species reproduce by binary fission. They are unicellular, although some species with yeast forms may become multicellular due to way in which they normally reproduce. Typically the size of a yeast cell is approximately 3-4 µm in diameter but this can vary greatly depending on the species. The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years. It is also extremely important as a model organism in modern cell biology research, and is the most thoroughly researched eukaryotic microorganism. Researchers can use it to gather information into the biology of the eukaryotic cell and human biology. These microbes are thought to be one of the first domesticated organisms. People have used yeast for fermentation and baking throughout history. Archaeologists digging in Egyptian ruins found early grinding stones and baking chambers for yeasted bread, as well as drawings of 4,000-year-old bakeries and breweries. It has many

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Electrochemical Cells

Electrochemical Cells Tam Paul-Worika Contents Aim of the Investigation.....................................................3 Background.....................................................................3 * Redox Reactions * Electrochemical Cells * Salt Bridge * Nernst Equation Plan.................................................................................5 * Equipment * Risk Assessment * Instructions * Making the solutions Analysis...........................................................................7 Evaluation......................................................................17 Aim of the Investigation In my investigation, I will observe how changing the concentration of a solution can affect the electrode potential in an electrochemical cell. I will also see if there is a trend when the concentration is changed. Background Redox Reactions Redox reactions are reactions where the oxidation states of the atoms change[1]. The atoms are either oxidised or reduced, depending on if they lose or gain electrons. Electrochemical Cells Electrochemical cells (also known as Galvanic cells or Voltaic cells[2]), are devices that cause a current from chemical reactions. These reactions occur through redox. An electrochemical cell is set up so that the electrons lost from one of the reagents can travel to another reagent. This creates a voltage, which

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Stereochemistry of Butenedioic acid

Name: Tonny, Chan Kar Yu, Student ID: 10297729 Date of Experiment: 19th February 2005, Group: B1 Title: Stereochemistry of Butenedioic acid Objective: To study the interconversion of two geometric isomers, maleic acid (cis isomer) to fumaric acid (trans isomers), the differences in physical properties between this pair of cis-trans isomers and determine the stereochemistry of addition of bromine to butenedioic acid. Chemicals and Apparatus: 2 grams of maleic acid, 10 cm3 of concentrated hydrochloric acid, 10 cm3 of bromine water1, one 50 cm3 beaker, one 100 cm3 beaker, one 250 cm3 beaker, one 10 cm3 measuring cylinder, one piece of spatula, one piece of water glass, one glass rod, a few pieces of filter paper, a set of Buchner funnel, a filter flask with side tube, three glass capillary tubes, a set of melting point apparatus, one long hollow glass tubing, one electronic balance, one heater and the oven Background: Stereochemistry is always encountered throughout organic chemistry. And stereochemistry isomerism can be divided into two classes, geometrical isomerism and optical isomerism. Although these categories are not mutually exclusive, it is not uncommon to find compounds that exhibit only one or the other of the two types. Most geometrical isomers result from cyclic systems or restricted rotation about double bonds. The preparation of fumaric acid by

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Making Aspirin

In this task we were asked to synthesise aspirin from salicylic acid (2 - hydroxybenzoic acid) and ethanoic anhydride (CH3COOCOCH3) in a laboratory scale and prepare a pure silver chloride sample from the solutions of silver nitrate (AgNO3) and sodium chloride (NaCl) of known concentrations. Now I am going to describe the preparation of these two items and estimate the purity of one of my samples. Preparation of aspirin: Now I am going to explain the preparation of the aspirin; Materials : (a) ethanoic acid (b) ethanoic anhydride (c) salicylic acid (d) water cooled condenser (e) filter paper (f) Buchner funnel (g) vacuum oven (h) melting point recorder machine etc. Procedure ) Firstly we mixed 5 ml of ethanoic acid with 5 ml of ethanoic anhydride in a 50 ml round bottomed flask. 2) After that we added 5 g of 2- hydroxybenzoic acid and a few anti - bumping stones . 3) Then we attached a water cooled condenser and reflux the mixture for 30 minutes over a Bunsen and gauze. 4) Then we pour the mixture slowly into 100 ml of cold water which is being stirred vigorously. 5) After that we removed the 2 - ethanoyloxybenzoic acid by filtration through a Buchner funnel. 6) Then we removed the product from the fume cupboard and dried it in a vacuum oven at about 80 degree Celsius. 7) Then we weight the dried product and recorded its melting point. Chemical reaction:

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Investigation of Enzyme Activity

An Investigation of Enzyme Activity with different Substrate Concentrations. Aim To investigate how different concentrations of substrate affects the rate of enzyme activity. Objective My objective is to determine how different concentrations of substrate, affects the rate of enzyme activity. I will do this by using different concentrations of Hydrogen Peroxide, and mixing it with the enzyme catalyse. Then I will measure how much gas is produced. Theory What is an Enzyme? Enzymes are proteins which are biological catalysts. A catalyst in chemical terms substantially reduces the energy barrier which exists between atoms and which prevents the atoms from getting close enough to react and form a bond with one another. An enzyme lowers the energy of activation of a reaction but the catalyst is not changed in any way in the process .Therefore, when the atoms of molecules are acted upon by enzymes, an identical reaction occurs as would have occurred without the enzyme but, the energy hill required to overcome the getting-close barrier, is much, much smaller than would have been true without the enzyme's help. The structure of the enzyme is such that atoms of molecules can get close enough to interact, but the energy required to allow this closeness is relatively small. Its like going into an empty closet with someone relative to going into an empty auditorium with someone.

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