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Biology of depression
Error bars or not? It involves a nearly painless finger prick to get a very small amount of blood that is dried on filter paper and mailed back to us with a completed questionnaire. Chemical Sampling Information Database " The rationale is that if you need to photocopy or fax your paper, any information conveyed by colors will be lost to the reader. Glycolysis Practice 1 page Review 1 page Concept 3: Tables present lists of numbers or text in columns, each column having a title or label.

Ethers and epoxides

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In a typical Benedicts Test shown below , approximately 1 ml of sample is placed into a clean test tube along with10 drops of Benedict's reagent CuSO 4. The reactions are heated in a boiling water bath for 5 minutes. The test solutions and Benedict's reagent are boiled in a water bath for five minutes.

Results of several solutions tested with the Benedict's test. Draw a large chart containing four equally divided columns and seven rows. In the first column, label rows with the appropriate samples below: In the second column labeled "Color of Heated Reactions", indicate the results of the Benedict's test after the reaction was heated. In the fourth column, draw the reacting functional group s of the samples that reacted with the benedict's reagent.

Iodine solution IKI reacts with starch to produce a dark purple or black color. Iodine is not very soluble in water, therefore the iodine reagent is made by dissolving iodine in water in the presence of potassium iodide. This makes a linear triiodide ion complex which is soluble. The triiodide ion slips into the coil of the starch causing an intense blue-black color. If you were to set up an Iodine test, you would perform the following: Use a wax marker to mark two test tubes 1 cm from the bottom.

Be sure to stir the starch before filling your tube. Add two drops of IKI solution to each tube and note any precipitation or color change. Design a chart and record your predictions for the starch test for reaction tubes Include in your chart the following headings: The results of a positive and negative control have been included in reaction tubes 1 and 2, respectively, for your convenience.

Is glucose a starch or reducing sugar? Is rice a starchy food or reducing sugar? Draw a potato cell in the space provided. Label the cell wall and starch granules. Although ethers contain two polar carbon-oxygen bonds, they are much less reactive than alcohols or phenols.

Epoxides are cyclic ethers that contain a three-membered ring. The simplest example is oxirane ethylene oxide. An epoxide is one of the functional groups in the insect hormone known as juvenile hormone. A thiol is structurally similar to an alcohol but contains a sulfur atom in place of the oxygen atom normally found in an alcohol. The outstanding feature of thiols is their foul smell.

The simplest thiol is hydrogen sulfide , H 2 S, the sulfur analog of water. It can be detected by the human nose at a concentration of a few parts per billion and is readily identifiable as having a rotten-egg odour.

Ethanethiol is added in trace amounts to natural gas to give it a detectable odour, and striped skunks deter predators by releasing a liquid spray containing 3-methylbutanethiol. When present as a substituent on another structural unit, the SH group is commonly termed mercapto , as in 2-mercaptoethanol. Amines are functional group compounds that contain at least one nitrogen atom bonded to hydrogen atoms or to alkyl or aryl groups.

If the substituents other than hydrogen atoms are alkyl groups, the resulting compounds are termed alkyl amines. If one or more substituents is an aryl group, the compounds are termed aryl amines. Amines are commonly categorized as primary, secondary, or tertiary, depending on whether the nitrogen atom is bonded to one, two, or three alkyl or aryl groups, respectively.

The resulting compound , called a quaternary ammonium salt , has a positive charge on the nitrogen atom and a tetrahedral arrangement of groups around the nitrogen atom. Amines are very common organic molecules, and many are physiologically active. Amphetamine , for example, is a central nervous system stimulant and acts as an antidepressant. Amines are particularly valuable because of their ability to act as bases, a property that is a consequence of the ability of amines to accept hydrogen atoms from acidic molecules.

Halides, or organohalides , are compounds that contain a halogen atom fluorine , chlorine , bromine , or iodine bonded to a carbon atom by a polar bond. The slightly positive charge that exists on the carbon atom in carbon-halogen bonds is the source of reactivity of halides.

A wide variety of organohalides have been discovered in marine organisms, and several simple halide compounds have important commercial applications. Chloroethane ethyl chloride is a volatile liquid that is used as a topical anesthetic. Chloroethene vinyl chloride is the monomeric building block for polyvinyl chloride PVC , and the mixed organohalide halothane is an inhalation anesthetic. The compound epibatidine, isolated from glands on the back of an Ecuadorian poison frog , has been found to be an especially potent painkiller.

When an oxygen atom forms a double bond to a carbon atom, a carbonyl functional group is obtained. The carbon atom of a carbonyl group is bonded to two other atoms in addition to the oxygen atom. A wide range of functional groups are produced by the presence of different atomic groupings on the carbon of the carbonyl group. Two of the most important are aldehydes and ketones. In a ketone , both atoms bonded to the carbonyl carbon are other carbon atoms, and, in an aldehyde , at least one atom on the carbonyl carbon is a hydrogen.

Many aldehydes and ketones have pleasant, fruity aromas, and these compounds are frequently responsible for the flavour and smell of fruits and vegetables. A 40 percent solution of formaldehyde in water is formalin , a liquid used for preserving biological specimens. Benzaldehyde is an aromatic aldehyde and imparts much of the aroma to cherries and almonds. Butanedione, a ketone with two carbonyl groups, is partially responsible for the odour of cheeses.

Civetone, a large cyclic ketone, is secreted by the civet cat and is a key component of many expensive perfumes. The carbonyl group has a wide variety of reaction pathways open to it. Whereas carbon-carbon double bonds are nonpolar, carbon-oxygen double bonds are polar.

The energy relationships of carbonyl addition reactions are consequently very different from those of alkene addition reactions. Other reaction possibilities of carbonyl compounds depend on the nature of the atomic groupings, termed substituents , attached to the carbonyl carbon.

When both substituents are unreactive alkane fragments, as in ketones, there are few reactions other than carbonyl additions. When one of the substituents is not an alkane fragment, different possibilities emerge. In aldehydes, the carbonyl carbon is bonded to a hydrogen atom, and reactions that involve this hydrogen atom distinguish the reactions of aldehydes from those of ketones.

The conjunction of a carbonyl and a hydroxyl group forms a functional group known as a carboxyl group. The hydrogen of a carboxyl group can be removed to form a negatively charged carboxylate ion , and thus molecules containing the carboxyl group have acidic properties and are generally known as carboxylic acids.

Vinegar is a 5 percent solution of acetic acid in water, and its sharp acidic taste is due to the carboxylic acid present. Lactic acid provides much of the sour taste of pickles and sauerkraut and is produced by contracting muscles. Citric acid is a major flavour component of citrus fruits, such as lemons, grapefruits, and oranges. Ibuprofen , an effective analgesic and anti-inflammatory agent, contains a carboxyl group. The structural unit containing an alkyl group bonded to a carbonyl group is known as an acyl group.

A family of functional groups, known as carboxylic acid derivatives , contains the acyl group bonded to different substituents. Each type of acid derivative has a set of characteristic reactions that qualifies it as a unique functional group, but all acid derivatives can be readily converted to a carboxylic acid under appropriate reaction conditions.

Many simple esters are responsible for the pleasant odours of fruits and flowers. Methyl butanoate, for example, is present in pineapples. Urea , the major organic constituent of urine and a widely used fertilizer , is a double amide of carbonic acid. Acyl chlorides and anhydrides are the most reactive carboxylic acid derivatives and are useful chemical reagents, although they are not important functional groups in natural substances.

Although each of the functional groups introduced above has a characteristic set of favoured reactions, it is not always possible to predict the properties of organic compounds that contain several different functional groups.

In polyfunctional organic compounds, the functional groups often interact with one another to impart unique reactivity patterns to the compounds. As chemistry evolves as a science , it becomes possible to understand more of the behaviour of complex molecules, and chemists are able to design laboratory syntheses of increasingly complicated molecules, basing the synthetic plan upon the reactivity trends of functional groups.

Chemical synthesis is concerned with the construction of complex chemical compounds from simpler ones. A synthesis usually is undertaken for one of three reasons. The first reason is to meet an industrial demand for a product. For example, ammonia is synthesized from nitrogen and hydrogen and is used to make, among other things, ammonium sulfate , employed as a fertilizer ; vinyl chloride is made from ethylene and is used in the production of polyvinyl chloride PVC plastic.

In general, a vast range of chemical compounds are synthesized for applications as fibres and plastics , pharmaceuticals , dyestuffs , herbicides , insecticides , and other products. Second, an enormous number of compounds of considerable molecular complexity occur naturally, in both living organisms and their degradation products; examples are proteins in animals and alkaloids alkaline materials found in plants.

The syntheses of these natural products have usually been undertaken in the context of the determination of the structures of the compounds; if a material is deduced to have a particular structure on the basis of its chemical reactions and physical properties, then the discovery that a compound synthesized by an unambiguous method for this structure is identical to the natural product provides confirmation of the validity of the assigned structure.

Third, a synthesis may be carried out to obtain a compound of specific structure that does not occur naturally and has not previously been made. This type of synthesis is performed in order to examine the properties of the compound and thereby test theories of chemical structure and reactivity.

The range of compounds that are capable of being synthesized is essentially limitless. They are not usually very selective. In contrast enzymes are usually highly selective, catalysing specific reactions only. This specificity is due to the shapes of the enzyme molecules.

Many enzymes consist of a protein and a non-protein called the cofactor. The proteins in enzymes are usually globular. The intra- and intermolecular bonds that hold proteins in their secondary and tertiary structures are disrupted by changes in temperature and pH.

This affects shapes and so the catalytic activity of an enzyme is pH and temperature sensitive. For two molecules to react they must collide with one another. They must collide in the right direction orientation and with sufficient energy.

Sufficient energy means that between them they have enough energy to overcome the energy barrier to reaction. This is called the activation energy. Enzymes have an active site. This is part of the molecule that has just the right shape and functional groups to bind to one of the reacting molecules. The reacting molecule that binds to the enzyme is called the substrate.

An enzyme-catalysed reaction takes a different 'route'. The enzyme and substrate form a reaction intermediate. Its formation has a lower activation energy than the reaction between reactants without a catalyst.

So the enzyme is used to form a reaction intermediate, but when this reacts with another reactant the enzyme reforms. This is the simplest model to represent how an enzyme works. The substrate simply fits into the active site to form a reaction intermediate. In this model the enzyme molecule changes shape as the substrate molecules gets close.

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