Human Biochemistry

Fats and oils are triesters (triglycerides) formed from the condensation reaction of propane-1,2,3-triol (glycerol) with long chain carboxylic acids (fatty acids).

Structure and melting points of fatsThe functional group of a carboxylic acid is the COOH HOHOHOCCCOOORRR80Student notesStructure and melting points of fatsFats and oils are triesters (triglycerides) formed from the condensation reaction of propane-1,2,3-triol (glycerol) with long chain carboxylic acids (fatty acids).

H2CThe general formula for a fat or oil (R, R and R are long chain hydrocarbons). HCH2COOOCCCOOORRRH2OH2OH2ORemember: Alcohol + Acid Ester + Water81Student notes Part of a healthy diet?Generally polyunsaturated oils are thought to be better for health than fats as they reduce the risk of heart disease.A diet high in saturated fats can produce high levels of cholesterol in the body which can lead to blocking of arteries. 82Student notes Differences in TmNameStructural formulaNumber of Carbon atoms.Number of C=C bondsTm/ oCLauric acid44.2Palmitic acid67.2Stearic acid69.6Oleic acid10.5Linoleic acid- 5Copy the table and use the data book to fill in the rest of the data. Can you describe the trend?CH3(CH2)10COOHCH3(CH2)14COOHCH3(CH2)16COOH CH3(CH2)7CH=CH(CH2)7COOHCH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH12161818180001283Student notes Differences in TmNameStructural formulaNumber of Carbon atoms.Number of C=C bondsTm/ oCLauric acid44.2Palmitic acid67.2Stearic acid69.6Oleic acid10.5Linoleic acid- 5Copy the table and use the data book to fill in the rest of the data. Can you describe the trend?CH3(CH2)10COOHCH3(CH2)14COOHCH3(CH2)16COOH CH3(CH2)7CH=CH(CH2)7COOHCH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH12161818180001284Student notes Melting pointsStearic acid and linoleic acid both contain the same number of carbon atoms and have similar molar masses but they have a different structure.

85Student notes

Proteins7Student notesExplaining difference in Tm.The regular tetrahedral arrangement of saturated acids means that they can pack closely together, so the van der Waals forces holding the molecules together are stronger as the surface area between them is greater.

This packing arrangement is similar in fats and explains why unsaturated fats, (oils) have lower melting points.

87Student notesIn Context This seems to be a significant factor in influencing the triglyceride composition produced by different organisms.Animal fats are usually richer in saturated fatty acids than plant oils are. In warm blooded animals, body temperature is high enough to allow most fats to be above their melting temperature. This means that they can be transported around the body as liquids.These fats tend to be highly saturated, with a high content of palmitic acid and stearic acid.88Student notesIn Context Plants have no means of keeping themselves warm when faced with cold conditions.

Plant oils must therefore have lower melting points and are often highly unsaturated.They contain high proportions of oleic acid and linoleic acid.Fish oils are highly unsaturated for similar reasons. They contain long fatty acid groups with as many as six C=C bonds.89Student notesIn summary a slightly polar region or head formed from the propane-1,2,3-triol molecule and the ester groups.A triglyceride molecule consists of:a non polar tail, formed by the three long chain fatty acids.

90Student notes Addition reactions Unsaturated fats can undergo addition reactions.

The addition of iodine to unsaturated fats can be used to determine the number of C = C double bonds since one mole of iodine will react quantitatively with one mole of double bonds.Show the reaction of iodine with ethene.CH2 = CH2+I2CIHHICHH1 mol of I2

1 mol of double bondsPurpleColourless:95Student notesForming polypeptidesTwo 2-amino acids can condense together to form a dipeptide with the elimination of water.

Two 2-amino acids can react differently to form two different dipeptides.Peptide BondsThe link between them, which has the structure:

is known as a peptide bond.The dipeptides still contain a reactive functional group on each end so they can react further in the presence of enzymes to form long chains of amino acid residues linked by peptide bonds.This is an example of condensation polymerisation and the products are known as polypeptidesCNOHCondensation Polymerisation

Activity:Draw the following dipeptides:Ala ArgArg AlaGlu GlyLeu LysPhe - SerContentsDescribe and explain the primary, secondary (-helix and -pleated sheets), tertiary and quaternary structure of proteins. Structure of proteinsThere are four levels of structure to describe proteins; primary, secondary, tertiary and quaternary.Primary structure the amino acid sequence in the polypeptide chainSecondary structure the -helix (intramolecular) and -pleated sheets (intermolecular) held by hydrogen bonding.Tertiary structure overall folding of the protein molecule held by interactions between distant amino acids Quaternary structure fitting together two or more separate protein chains to give the final physiologically active protein.

Primary structureProteins are made up from a fixed number of amino acid residues connected to each other in a unique linear sequence, this is the primary structure.The primary structure is usually depicted by a three-letter short-hand notation, e.g. ala for alanine, leu for leucine and so on arranged in the appropriate sequence.

Secondary StructureThe chain of amino acids that makes up the primary structure of a protein can fold itself in two ways, depending on the sequences of amino acids that are next to each other. The alpha helix (-helix)The beta pleated sheet (-pleated sheets) Hydrogen bonds hold the folded structures in place.This folding of the primary structure is called the secondary structure

Tertiary structureThis is the overall folding of the chain held by interactions between more distant amino acids.These interactions include Hydrogen bonds Disulphide bridges (these are covalent bonds that form between sulphur atoms on the oxidation of two cysteine amino acids as well as ionic interactions and intermolecular forces.Van der Waals attraction between non-polar side groups.Ionic attractions between polar groups Peptide bonds between molecules with more than one amine or acid group.

What interactions are occurring between these adjacent polypeptide chains?

Quaternary StructureSeparate polypeptide chains can interact together to give a more complex structure; this is known as the quaternary structure.Haemoglobin has a quaternary structure that includes four protein chains (two -chains and two chains) grouped together around four haem groups.Insert picture of haemoglobinStudent notes

ContentsExplain how proteins can be analysed by chromatography and electrophoresis Analysis of ProteinsTo determine the primary structure of a protein it must be first completely hydrolysed using the reagent concentrated hydrochloric acid and boiled for 24 hours to successively release the amino acids.These can then be identified by:Paper chromatography Polyacrylamide Gel Electrophoresis PAGE.Paper chromatographyPaper largely consists of cellulose fibres, these contain a large number of hydroxyl groups, making the paper quite polar. Water molecules hydrogen-bond to these groups, so that a sheet of dry paper actually consists of about 10% water.It is this water that acts as the stationary phase, the mobile phase is a solvent, either water itself or a polar organic liquid such as ethanol, propanone or ethanoic acid.ActivityCarry out Paper Chromatography Expt: (?) on the mixture of amino acids to find out which amino acids are present in the mixture.

The container is closed in order to saturate the atmosphere within it and prevent evaporation of the solvent from the paper to give better and faster separation.Student notesPolyAcrylamide Gel ElectrophoresisIn PAGE the sample is placed in the centre of a polyacrylamide gel and a potential difference is applied across it.Depending on the pH of the buffer, the different amino acids will move at different rates towards the positive and negative electrodes.At its isoelectric point (the pH at which it forms a zwitterion), a particular amino acid will not move, because its charges are balanced.When separation is complete the amino acids can be sprayed with ninhydrin and identified by comparing the distance they have travelled with standard samples or from a comparison of isoelectric points. ContentsB7 AHL EnzymesDescribe the characteristics of biological catalysts (enzymes)Compare inorganic catalysts and biological catalysts (enzymes)Describe the relationship between substrate concentration and enzyme activity.Determine Vmax and the value of Michaelis constant (Km) by graphical means and explain its significance.Describe the mechanism of enzyme action, including enzyme substrate complex, active site and induced fit model.Compare competitive inhibition and non-competitive inhibition.State and explain the effects of heavy-metal ions, temperature changes and pH changes on enzyme activity.33Student notesEnzymesEnzymes are protein molecules that catalyse biological reactions.Each enzyme is highly specific for a particular reaction, and extremely efficient, often able to increase the rate of reaction by more than one hundred million times.Like all catalysts, enzymes work by providing an alternative pathway for the reaction with a lower activation energy, by creating an environment in which the transition state is stabilized.

How enzymes workThe specificity of enzymes depends on their particular shape.This is determined by their secondary, tertiary and quaternary structure.The part of an enzyme that reacts with the substrate is known as the active site.This is the part of the enzyme where the substrate (reactants) will bind and undergo chemical reaction.The active site is not necessarily rigid, but can alter its shape to allow for a better fit known as the induced fit theory.

How enzymes workhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.htmlExample: how enzymes hydrolises sucrosehttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__enzyme_action_and_the_hydrolysis_of_sucrose.html

Enzyme KineticsAt low substrate concentrations the rate of reaction is proportional to the concentration of the substrate.However, at higher concentrations the rate reaches a maximum, known as Vmax. This can be explained in terms of enzyme saturation. At low substrate concentrations there are enough active sites present for the substrate to bind to and react.At Vmax all the sites are used up and the enzyme cannot work any faster.Vmax was first identified by a German-born American biochemist, Leonor Michaelis (1875-1949), and a Canadian doctor, Maud Menten (1879-1960).Michaelis Menton constant KmMichaelis and Menton went on to identify a constant in enzyme substrate reactions. Km, known as the Michaelis-Menton constant is the substrate concentration when the rate of the reaction is Vmax.

Km for a particular enzyme with a particular substrate will always be the same.It indicates whether the enzyme functions efficiently at low substrate concentrations or whether high substrate concentrations are necessary for the reaction to be catalysed efficiently.Animation: V maxhttp://www.wiley.com/college/boyer/0470003790/animations/enzyme_inhibition/enzyme_inhibition.htm

Inhibition of enzymesInhibitors are substances that decrease the rate of enzyme-catalysed reactions.There are two main types of inhibitors:Competitive inhibitors which resemble the substrate in shape but cannot react. They slow down the reaction because they can occupy the active site on the enzyme, thus making it less accessible to the substrate.Non-competitive inhibitors also bind to the enzyme, but not on the active site. This is thought to cause the enzyme to change its shape so that the substrate cannot bind. Animations: enzymes inhibitorshttp://www.wiley.com/college/pratt/0471393878/student/animations/enzyme_inhibition/index.htmlhttp://www.youtube.com/watch?v=PILzvT3spCQ

Affect of inhibitors with increasing substrate concentrationAs the substrate concentration is increased, the effect of competitive inhibitors will be diminished, because there is increased competition for the active sites by the substrates.With non competitive inhibitors, increasing the substrate concentration will not increase the effectiveness of the enzyme, because the enzymes shape still remains altered by the non competitive inhibitor.

Graphs to show the effect of inhibitors on Km

For competitive inhibitors Vmax is the same but Km is increased.

For non-competitive inhibitors Vmax is lower, but Km is the same.Factors affecting enzyme activitySeveral factors can affect the efficient functioning of enzymes.The catalytic action of an enzyme clearly depends on its specific shape. Its shape can be affected by the following factorsTemperaturepHHeavy metals Affect of temperatureIncreasing the temperature will initially increase the rate of enzyme-catalysed reactions, because more of the reactants will possess the minimum activation energy.The optimum temperature for most enzymes is about 40C. Above this temperature enzymes rapidly become denatured as the weak bonds holding together the tertiary structure become broken.

Affect of pHHigh and low pH can also affect enzymes in a similar way as temperature.Initially an increase in pH increases the rate of reaction until it reaches an optimum pH, the optimum pH depends on the enzyme.

At different pH values the charges on the amino acid residues change, affecting the bonds between them and so disrupting the specific tertiary structure and making the enzyme ineffective.

The affect of heavy metalsHeavy metals can poison enzymes by reacting irreversibly with SH groups, replacing them with a heavy metal atom or ion so that then tertiary structure is permanently altered.http://www.chemguide.co.uk/organicprops/aminoacids/enzymes3.html

Carbohydrates48Student notes ContentsList the major functions of carbohydrates in the bodyDescribe the structural features of monosaccharidesDraw straight chain and ring structural formulae of glucose and fructoseDescribe the condensation of monosaccharides to form disaccharides and polysaccharides.49Student notesWhere do we get them from?Carbohydrates are produced in plants by photosynthesis, this requires energy provided by sunlight.Write the word and balanced symbol equation for photosynthesis.

When taken into the human body the process is reversed in respiration, this in turn release a lot of energy.Write the word and balanced symbol equation for respiration.

Where do we get them from?Carbohydrates are produced in plants by photosynthesis, this requires energy provided by sunlight.Write the word and balanced symbol equation for photosynthesis.

When taken into the human body the process is reversed in respiration, this in turn release a lot of energy.Write the word and balanced symbol equation for respiration.

xCO2 + yH2O Cx(H2O)y + xO2carbon dioxide + water glucose + oxygenCx(H2O)y + xO2 xCO2 + yH2Oglucose + oxygen carbon dioxide + waterWhat are they, and where do they come from?Carbohydrates are given the general formula:Cx(H2O)yCarbohydrates can be found in foods such as: bread biscuitscakespotatoesrice cereals.Major functions in the bodyThe uses of carbohydrates in the body include;Source of chemical energyEnergy store (in the livers and skeletal muscles of animals it is stored in the form of glycogen known as animal starch).Precursors for other important molecules e.g. they are components of nucleic acids and play a key role in the biosynthesis of proteins.Cellulose, hemicellulose, lignin and pectin, collectively known as dietary fibre is needed to providegood bowel movements.

MonosaccharidesThe simplest sugars are called monosaccharides.Monosaccharides have the empirical formula CH2O and contain a carbonyl group (C =O) and at least two hydroxyl, -OH, groups.They generally have between three and six carbon atoms.Monosaccharides with the general formula; C5H10O5 are called pentoses e.g. riboseC6H12O6 are called hexoses e.g. glucoseGlucoseThe most common hexose is glucose, in nature the form of glucose that is found is known as D-glucose, it can exist as both a straight chain molecule or a cyclic (ring) structure.The ring structure can have two separate crystalline forms known as -D-glucose and -D-glucose, the only difference between them is that the OH group on the first carbon atom is inverted.CH2OHCH2OHCCCCOHOHOHOHHHHHOHOHOHHOHHCH2OHHOHHOHOHOHHHCH2OHHOHHOH-D-glucose -D-glucoseOHOHOHHOHHCH2OHHOHHOHOHOHHHCH2OHHOHHOHPolysaccharidesSugars can condense together in the presence of appropriate enzymes to form polysaccharides.Sucrose is a disaccharide formed form the condensation of -D-glucose and -D-fructoseThe link between the two sugars is known as a glycosidic link.In the case of sucrose the link is between the C-1 atom of glucose in the configuration and the C-2 atom of fructose.The link is known as an -1,2 bond

Lactose is a disaccharide in which the -D-galactose is linked at the C-1 atom to the C-4 atom of -D-glucose, this is called a -1,4 linkage.

OHOHOHHHCH2OHHOHHOH453216-D-glucoseOHOHOHHHCH2OHHOHHOH-D-galactose453216O-1,4 linkageLactoseMaltose is formed when two -glucose molecules condense, forming an -1,4 linkage.

OHOHOHOHHHCH2OHHOHHOHOHOHHOHHCH2OHHOHH-D-glucose-D-glucoseOmaltose-1,4 linkage123456453216ObjectivesCompare the structural properties of starch and cellulose, and explain why humans can digest starch but not cellulose.

Starch - polysaccharidesOne of the most important polysaccharides is starch.Starch exists in two forms:Amylose (soluble in water)Amylopectin (insoluble in water)AmyloseAmylose is a straight-chain polymer of-D-glucose units with -1,4 bonds. OHOHHOHCH2OHHOHHOOHOOHHHCH2OHHOHH-1,4 linkageAmylopectinOHOHHOHCH2OHHOHHOOHOOHHHCH2HOHHOHOHHOHCH2OHHOHHOOHOOHHHCH2OHHOHH-1,4 linkage-1,4 linkage-1,6 linkageAmylopectin also consists of -D-glucose units, but it has a branched structure with both -1,4 and -1,6 bonds ObjectivesState what is meant by the term dietary fibreDescribe the importance of a diet high in dietary fibre.Compare the structural properties of starch and cellulose, and explain why humans can digest starch but not cellulose.Dietary fibre - roughageDietary fibre is mainly plant material that cannot be hydrolysed by enzymes secreted in the human digestive tract, although it can be digested by microflora in the gut.Roughage is needed to provide good bowel movements, and a lack of dietary fibre can lead to:DiverticulosisIrritable bowel syndromeConstipationObesityHaemorrhoidsDiabetesBowel cancerCelluloseCellulose is a polymer of -D-glucose which contains -1,4 linkages.Cellulose together with lignin, provides the structure to the cell walls of green plants.Most animals including all animals do not have the enzyme cellulase and so are unable to digest cellulose or other dietary fibre polysaccharides.http://pslc.ws/macrog/kidsmac/starlose.htm

Major functions in the bodyThe uses of carbohydrates in the body include;Source of chemical energyEnergy store (in the livers and skeletal muscles of animals it is stored in the form of glycogen known as animal starch).Precursors for other important molecules e.g. they are components of nucleic acids and play a key role in the biosynthesis of proteins.Cellulose, hemicellulose, lignin and pectin, collectively known as dietary fibre is needed to providegood bowel movements.

Lipids68Student notes ContentsCompare the composition of the three types of lipids found in the human body.Outline the difference between HDL and LDL cholesterol and outline its importance.69Student notesLipidsLipids are organic molecules with long hydrocarbon chains that are soluble in non-polar solvents. They are used mainly for; energy storage insulating and protecting vital organs, forming cell membranes acting as hormones.Three important types of lipids are steroids (cholesterol), triglyderides (fats and oils) and phospholipids (lecithin). Steroids (Cholesterol)Cholesterol has the characteristic four-ring structure possessed by all steroids.

It is formed in the liver, and is found in all tissues, the blood, brain and spinal cord.It is transported by lipoproteins. OHCH3CH3CHCH2CH2CH2H3CCCH3CH3HLipoproteins (503)There are two main types of lipoproteinsLow density lipoproteins (LDL) High density lipoproteins (HDL)Low-density lipoproteins (LDLs)These are in the order of 18-25 nm and transport cholesterol to the arteries, where they can line the walls of the arteries, leading to cardiovascular diseasesThe major source of these LDLs are saturated fats and in particular those derived from lauric (C12), myristic (C14) and palmitic (C16) acids High-density lipoproteins (HDLs)These are smaller lipoproteins in the order of 8-11nm.These can remove the cholesterol from arteries and transport it back to the liver.ContentsB8 AHL Nucleic acidsDescribe the structure of nucleotides and their condensation polymers (nucleic acid or polynucleotides).Distinguish between the structures of DNA and RNAExplain the double helical structure of DNA.Describe the role of DNA as the repository of genetic information, and explain its role in protein synthesis.Outline the steps involved in DNA profiling and state its use.

Nucleic acidsNucleic acids are natural polymers with Relative Molecular Masses of up to several million made up of nucleotides.All cells in the human body , with the exception of red blood cells, contain DNA

ContentsDescribe the difference in structure between saturated and unsaturated fatty acids.Compare the structures of the two essential fatty acids linoleic (omega-6 fatty acid) and linolenic (omega-3 fatty acid) and state their importance.Define the term iodine number and calculate the number of C=C double bonds in an unsaturated fat/oil using addition reactions.Describe the condensation of glycerol and three fatty acid molecules to make a triglyceride.

Most plant oils contain several carbon-to-carbon double bonds and are known as polyunsaturated.In the body, fats and oils are hydrolysed by enzymes, known as lipases, to glycerol and fatty acids.These in turn are broken down by a series of redox reactions to produce, ultimately, carbon dioxide, water and energy.Fats are in a less oxidised form than carbohydrates (they are essentially long-chain hydrocarbons with only two oxygen atoms each on the three carboxyl atoms), so weight for weight produce more energy.Linoleic acidsThe body requires two essential unsaturated fatty acids that it is unable to synthesize.These are; -6 linoleic acid-3 linolenic acid.From these the body is able to synthesise longer and more unsaturated fatty acids.Green leaves are a good source of -3 fatty acids, whereas most seeds and vegetable oils are a good source of -6 fatty acids

Naming linoleic acidsThe double bonds in linoleic acid are on the ninth and twelfth carbon atoms of the acid, but it is known as an omega () - 6 fatty acid because the first double bond is on the sixth carbon atom from the end of the hydrocarbon chain (that is, counting from the other end).

-3 fatty acids have the first double bond on the third carbon atom from the end of the hydrocarbon chain.OHCH3CH2CH2CH2CH2CH2CH2CCH2CH2CH2CH2CH2HCCCHHHCH2COThe structure of the cis, cis- form of linoleic acidPhysiologogists count from the hydrocarbon end!92Student notesSynthetic fatty acidsWhen fatty acids are made synthetically by partially hydrogenating other polyunsaturated fatty acids, then the trans- isomers may be formed.Trans-fatty acids are present in fried foods such as French fries and some margarines.They increase the formation of LDL cholesterol and thus increase the risk of heart disease.CH2CH2CH2CH2CH2CH2CCH2CCH2CH2CH2HCCH2CHHHCH2COOHThe structure of the trans, trans- form of linoleic acidThe structures of linoleic acidOHCH3CH2CH2CH2CH2CH2CH2CCH2CH2CH2CH2CH2HCCCHHHCH2COCH3CH2CH2CH2CH2CH2CH2CCH2CCH2CH2CH2HCCH2CHHHCH2COOHThe structure of the trans, trans- form of linoleic acidThe structure of the cis, cis- form of linoleic acidAddition reactions.As the iodine is added to the unsaturated fat the purple colour of the iodine will disappear as the addition reaction takes place.Often fats are described by their iodine numberThe iodine number is the number of grams of iodine, that add to 100g of the fat.ContentsDescribe the enzyme-catalyzed hydrolysis of triglycerides during digestion.Explain the higher energy value of fats as compared to carbohydratesDescribe the important roles of lipids in the body and the negative effects that they can have on health.

Major functions of fats in the bodyFats provide a very efficient way for the body to store energy.Fats contain proportionately less oxygen than carbohydrates, so when they are oxidized in the body they release more energy. Fats are stored in adipose (fatty) tissue, which provides both thermal insulation and protection to parts of the body.Fats also form part of cell membranes.

Hormones99Student notesContentsOutline the difference between micronutrients and macronutrientsCompare the structures of retinol (vitamin A), calciferol (vitamin D) and ascorbic acid (vitamin C).Deduce whether a vitamin is water- or fat-soluble from its structure.Discuss the causes and effects of nutrient deficiencies in different countries and suggest solutions.

100Student notesHormones are chemicals produced in glands and transported to the site of action by the blood stream. The glands themselves are controlled by the pituitary gland, which in turn is controlled by the hypothalamus.Hormones act as chemical messengers and perform a variety of different functions.Examples of specific hormones include adrenaline, thyroxine, insulin and the sex hormones.General PropertiesAdrenaline (epinephrine) is produced in the adrenal glands two small organs located above the kidneys.It is a stimulant closely related to the amphetamine drugs.It is released in times of excitement and causes rapid dilation of the pupils and airways and increases heartbeat and the rate of sugar release into the blood stream.It is sometimes known as the fight or flight hormone.

AdrenalineThyroxine is produced in the thyroid gland located in the neck.Thyroxine regulates the bodys metabolism.It is unusual as it contains iodine.A lack of iodine in the diet can cause the thyroid gland to swell to produce a condition known as a goitre.

Overactive thyroid hyperthyroidism symptoms of anxiety, weight loss, intolerance to heat and protruding eyesLow levels cause hypothyroidism lethargy, sensitivity to cold and dry skinThyroxineInsulin is a protein containing fifty-one amino acid residues.It is formed in the pancreas - an organ located at the back of the abdomen and regulates blood sugar levels.In diabetics the levels of insulin are low or absent and glucose is not transferred sufficiently from the blood stream to the tissues this is known as hyperglycaemia. This results in thirst, weight loss, lethargy, coma and circulation problems.Long term sufferers can suffer blindness, kidney failure, and need limbs amputated due to poor circulation.InsulinMale Sex HormonesThe male sex hormones are produced in the testes, and comprise mainly testosterone and androsterone. They are; Anabolic encouraging tissue, muscle and bone growthAndrogenic conferring the male sexual characteristics

Female Sex HormonesThe female sex hormones are structurally very similar, with just small changes in the functional groups attached to the steroid framework.They are produced in the ovaries from puberty until the menopause.The two main female sex hormones are oestradiol and progesterone.They are responsible to sexual development, and for the menstrual and reproductive cycles in women.Oral contraceptivesAt the beginning of the menstrual cycle the pituitary releases the follicle-stimulating hormone (FSH).FSH travels to the ovaries, causing the release of the ovum or egg and the build-up of the uterine wall.Vitamins108Student notes ContentsCompare the structures of retinol (vitamin A), calciferol (vitamin D) and ascorbic acid (vitamin C).Deduce whether a vitamin is water- or fat-soluble from its structure.Discuss the causes and effects of nutrient deficiencies in different countries and suggest solutions.

109Student notesVitamins are substances with very different structures. Apart from vitamin D the body is not capable of synthesizing vitamins and cannot function correctly without them, so they must be obtained from food.A poor diet may lead to deficiency diseases.Vitamins can be classified as fat soluble or water solubleGeneral PropertiesThe structure of fat soluble vitamins is characterised by long non-polar hydrocarbon chains or rings.These include vitamins A,D,E,F and K.They can accumulate in the fatty tissues of the body.In some cases an excess of fat soluble vitamins can be as serious as a deficiency.

Fat SolubleThe molecules of water soluble vitamins, such as vitamin C and the eight B-group vitamins, contain hydrogen attached directly to electronegative oxygen or nitrogen which can hydrogen bond with water molecules.They do not accumulate in the body so a regular intake is required.

Water SolubleProlonged cooking destroys most vitamins.When boiling vegetables it is better to use small amounts of water and use the stock in gravy or soups to avoid loss of water soluble vitamins.Vitamins containing C=C double bonds and OH groups are readily oxidised and keeping food refrigerated slows down this process.Part of a healthy diet

Vitamin A is also called Retinol.It is a fat soluble vitamin. Unlike most other vitamins it is not broken down readily by cooking.Retinol is stored in the liverIt is found in cod liver oil, green vegetables and fruit as well as eggs, cheese, liver and milk.Vitamin ACarotene is a vitamin A precursor, it is the yellow pigment present in green leaves and carrots and is turned into retinol by the body.Retinol is oxidised by the body to form retinal. This combines with the protein opsin to form rhodopsin, the active agent for converting light signals into electrical signals that can travel along the optic nerve to the brain. If you suffer a deficiency in this vitamin you will have:Poor night visionA serious deficiency can lead to xeropthalmia, a chronic form of conjunctivitus, which is the commonest form of blindness in the Third World.Vitamin AUsing the computers find out information on Vitamin C and D.Information must include:Structural formulaWhat food it is present in.What problems can happen if you are deficient in it or have an excess.Any other relevant notes.ActivityThis is also called Ascorbic acid.It is found in fresh fruit and vegetables.It is a water soluble vitamincan you explain why?Due to the large number of polar -OH groupsCan it be stored in the body or is it excreted? How do you know?It is broken down by cooking, so raw vegetables provide a better source than boiled vegetables.Vitamin CThe various roles played by vitamin C are not fully understood.Claims that it is effective in preventing both the common cold and cancer appear to be unfounded.It does aid the healing of wounds and helps prevent bacterial infections.It is involved in the biosynthesis of protein collagen, found in connective tissue, such as cartilage, ligaments and tendons.Functions in the bodyThe most famous disease associated with a lack of vitamin C is scorbutus (scurvy).The symptoms are swollen legs, rotten gums, and bloody lesions.It was a common disease in sailors, who spent long periods without fresh food, until the cause was recognized.Vitamin C is easily oxidised. It can help to preserve food by being more readily oxidised than the food it is preserving.Deficiency diseasesVitamin D is also known as Calciferol.

Looking at the structure do your think it is fat soluble or water soluble?Explain your reasoning.Fat soluble, as it has only one polar OH group attached to it.It is found in fish liver oils and in egg yolk. It can be formed on the surface of the skin through the action of UV light in sunlight on 7-dehydrocholesterol.Vitamin DVitamin D is involved in the uptake of calcium and phosphate ions from food into the body and especially in the formation of bone structure.A deficiency of Vitamin D leads to bone softening and malformation a condition known as rickets.Vitamin D can be destroyed through oxidation by some of the bleaching agents used in the manufacture of purified flour.Function in the body[DEFAULT]BASEURL=http://www.youtube.com/watch?v=tDaKxskUwA0[{000214A0-0000-0000-C000-000000000046}]Prop3=19,2[InternetShortcut]URL=http://www.youtube.com/watch?v=tDaKxskUwA0IDList=IconFile=http://s.ytimg.com/yt/favicon-refresh-vfldLzJxy.icoIconIndex=1