2 OBJECTIVESAll should : be able to describe the structure of a water molecule,the H bonds that hold them together & and understand this is responsible for its unusual properties. Be able to describe some of the properties of water and link some to its structure and importance to living organismsSome may: be able to take this a stage further and give detailed explanations of how the H bonds in water control the properties that are so important for living organisms
6 The Elements of life 92 naturally occurring elements The atoms of only 16 are commonly found in living organisms4 account for 99% of the atoms found in living organisms,these are in order of abundance:H hydrogenC carbonO oxygenN nitrogenThis is because living organisms are made up of organic moleculesOthers are calcium(Ca),iron(Fe),potassium(K),sodium(Na), chlorine(Cl),sulphur(S) & magnesium(Mg)
7 Bonding Atoms are joined together to make molecules and compounds This is done by chemical bondsMost of the molecules making up living organisms have atoms joined by covalent bondsCovalent bonds are shown by lines.They can be single,double or treble.They are formed by sharing electronsGlycine – an amino acid
8 Covalent bondingCarbon always has 4 covalent bonds with other atoms. Terrestrial life forms are carbon based. This multiple bonding allows carbon to be a framework atomAll the biological molecules we will learn about use carbon as a framework atom.Other bonds formed are: Oxygen 2 ,hydrogen 1 & nitrogen 3ethanolethene
10 The building blocks of life Living organisms are mainly made up of macromolecules (giant molecules)These are polymers made up of many smaller monomers by a process called polymerisationThe main macromolecules are:PolysaccharidesNucleic acidsProteins (polypeptides)Lipids (fats)
11 The Building Blocks of life MONOMER POLYMEROrganic base, sugar & phosphateAmino acidsFatty acids & glycerolmonosaccharidenucleotidesNucleic acidspolysaccharidelipidsproteins
12 Carbohydrates All contain the elements carbon, hydrogen & oxygen The name comes from hydrated carbon!For every carbon atom there is a waterGeneral formula for carbohydrate isCn(H2O)nQ. Fructose has 6 carbons, what is it formula? What about ribose which is a pentose sugar?There are 2 types of carbohydrate:1. Simple sugars: Monosaccharide & Disaccharides2. Polysaccharides
13 Simple sugars: Monosaccharides Sugars – all end in -oseWhite,crystalline substances,dissolve easily in water to give sweet solutions.Single sugar molecule – mono = oneGeneral formula (C H2O)n where n is the number of carbon atomsSo if 6 carbon atoms(a hexose sugar) the molecular formula is C6H12O6What about pentose sugars(C5) or triose sugars(C3)?
14 Glucose Most important and widespread monosaccharide. Hexose sugar The 6 carbons are numberedFunction:Transported around in the blood and used in cells as a source of energy in respiration. The energy is released in the form of ATPStructural formula123456Molecular formula C6H12O6
15 The ring form of glucose The chain of carbons in hexose(and pentose) sugars is long enough to close up and form a more stable ring structureCarbon atom 1 joins to the oxygen on carbon atom 5
16 Glucose isomersThe new OH formed in the reaction can be above the ring - β glucose or below - α glucoseThese are isomers-two forms of the same chemical.
18 Roles of monosaccharides in living organisms A source of energy for respiration.Due to large number of C-H bonds which when broken release a lot of energyThis energy is used to make ATP(adenine triphosphate) from ADP(adenine diphosphate)Also used as building blocks to make larger molecules for example:Deoxyribose(pentose) used to make DNARibose used to make RNA and ATPGlucose makes up starch,cellulose and glycogen.
19 Disaccharide formation Two glucose molecules are held close together by an enzyme.Water is lost and a 1-4 glycosidic bond(link) formed .This is a condensation reactionThe new molecule is a disaccharide - maltose
23 Chemical test for saccharides(sugars) Reducing SugarsHeat the sugar solution with an equal volume of blue benedict's solution for 2-3 minutes at about 90°CA positive result is a brick red precipitateBenedicts solution contains blue Cu2+ ions, the sugar reduces this to the insoluble brick red Cu+ compoundCu Cu+ElectronFrom sugar
24 Non reducing sugar test Some sugars are non reducing.They do not reduce benedict's solutionOne example is sucrose, it must be hydrolysed(broken-down by adding water) to form glucose and fructoseThis can be done by heating with a few drops of acid at 90°C for a few minutes. Then neutralising the solution with an equal amount of sodium hydroxide solutionYou will then get a positive result when repeating the benedict's test
25 lactose fructose glucose sucrose maltose Sugar Type of saccharide? Result of benedicts test for reducing sugarResult of non-reducing sugar testReducing or non-reducing sugar?lactosefructoseglucosesucrosemaltose
26 Quantitative Estimation of glucose concentration in a solution Glucose solution(%)Weight of precipitate (g)Light Transmission of filtrate (%)0.010.050.10.51
27 Sugars homework a. Glyceraldehyde – C3 Triose Ribose C5 Pentose Glucose & Fructose C6 Hexoseb. Glucose is an aldose sugar H-C=O is on C1c.
29 e alpha glucose OH below the ring beta glucose OH above ringf alpha galactose
30 Polysaccharide- Structure & Function Polysaccharides are polymers made up of monosaccharide subunitsThe polymers can be many thousand monosaccharides – making macromoleculesMost important are starch,glycogen & celluloseAll are polymers of glucoseThey are insoluble in water and do not taste sweet.
31 Starch Made up of a mixture of two macromolecules Amylose (20%) and amylopectin (80%)
32 AmyloseAmylose is formed by condensation of a long chain of α glucose using 1α – 4 glycosidic bonds
33 Amylose α helixThe 1α – 4 glycosidic links in amylose mean the glucose monomers are at a slight angle to each otherThis causes a helix to formThis is stabilised by hydrogen bonds
34 Amylopectin Branching chains of α glucose Branches about once every 25 glucoseBranches formed by 1-6 glycosidic bondsThe branching structure gives many “ends” to attach new glucose or to remove it. So it is ideal for storing glucose
35 Starch – Role in living organisms Starch is a store of glucose in plantsPlants cannot store sugars as this would increase the osmotic potential (low water potential) of the cells,the solution inside the cells would be too concentrated.This would lead to ….Starch is insoluble and has no osmotic effect
36 Starch Grains In plants starch is stored as starch grains These are most often found in chloroplasts or in specialised plant structures such as seeds or tubers eg potatoesThe helical shape of amylose means it can be packed tightly
37 Chemical test for Starch Add iodine solution to the materialIodine solution is orange brownA blue black colour is produced on contact with starchThis is because the iodine molecules fit into the amylose helix giving the colour
38 Glycogen Starch is not found in animal cells Glycogen is used to store glucose in animal cellsIt is very similar to amylopectin but more branchedIt branches every 8-10 glucoses,again giving plenty of ends to add extra glucoseIt forms granules which can be seen in muscle & liver cells
39 Cellulose Cellulose makes up plant cell walls It is a structural polysaccharideIt is made up of β glucose where OH is above the ringIn order to form a glycosidic bond the other glucose must be upside down.The bond formed is a β1-4 glycosidic bond
40 Cellulose cross links Cellulose cannot form a helix It exists in long chainsChains lie side by side and hydrogen bonds form between themThese form between adjacent glucose molecules and between the chains.
41 This gives the cellulose molecule great mechanical strength They are insoluble,tough,durable and slightly elastic, ideal structural components60-70 chains are strongly linked together to form bundles called microfibrilsMicrofibrils are held together in fibresFibres make up the plant cell wall
43 Cellulose fibres are laid down in layers to form the cell wall Fibres are at right angles to increase strengthOther molecules help cross linkingOlder cell walls are reinforced with ligninA glue like matrix(pectins) is laid down in between the fibres to increase strengthSimilar to reinforced concrete
44 Cellulose – structure & function High tensile strength of cellulose fibres means they are difficult to break if pulled at both endsAllows the cell to withstand the pressure caused when water enters by osmosis.Gives plant cells strength and rigidityProvides supportDespite strength they are freely permeableEven though cellulose contains glucose it cannot be digested by most animals as they do not have the required enzyme cellulase
45 Other structural polysaccharides ChitinExoskletons of arthropodsPeptidoglycanCell wall of bacterial cells
48 LipidsThis group contains a wide range of molecules ranging from fats,oils,phospholipids,waxes & steroidsThey all contain the elements C,H & ONormally much less OThe most widespread are TRIGLYCERIDES also known as fats or oils
49 Triglyceride structure Made up of 3 FATTY ACID moleculesAnd 1 GLYCEROL molecule
50 Fatty Acid structureStearic acid an example of a saturated fatty acid.All the carbon atoms in the tail are full,”saturated” with hydrogenCan also be written asCH3(CH2)16COOH
51 The COOH group is called a CARBOXYLIC ACID group The long “tail” of the molecule is called a HYDROCARBON TAILThis hydrocarbon chain will not dissolve in water it is said to be non-polar or hydrophobic(water hating)
52 The carboxylic acid group is polar or hydrophilic(water loving)
53 Unsaturated Fatty Acids These fatty acids contain a double bondIt causes a “kink” in the tailThese fatty acids melt more easilyOne double bond is monounsaturatedMore than one are called polyunsaturated
54 Glycerol structureGlycerol is a type of alcohol with 3 alcohol groups.
55 Forming a triglyceride When glycerol combines with a fatty acid it forms a glycerideWhen it combines with 3 fatty acids it is a triglycerideThey combine in a condensation reaction, losing waterForming an ester link
56 PropertiesTriglycerides are insoluble in water, they are non-polar moleculesThe more unsaturated fatty acids the lower the melting point making these oils at room temperature, normally found in plantsAnimal fats have a higher melting point and are generally solid at room temperature due to saturated fatty acids
57 Roles of triglycerides ENERGY RESERVES- high number of C-H bonds so much more energy content than carbohydrate-so you need to store less to get the same energyIn humans stored around organs and under the skin
62 Phospholipid properties and roles These molecules have a hydrophobic tail and hydrophilic headThey form the membranes of living cells
63 Cholesterol Not formed from fatty acids and glycerol 4 carbon based ringsSmall hydrophobic moleculeFound between phospholipid tails in membranesControls membrane fluidity and mechanical strength
64 Excess cholesterol Many cells make cholesterol from saturated fats Especially liver cellsExcess can be deposited in artery wallsCausing atherosclerosis
65 Excess cholesterol is removed in bile It can form gallstones in the gall bladder
66 Steroid hormonesThese are made from cholesterol and include:
67 Chemical test for Lipids Emulsion testAdd ethanol to the suspect material and mix well (any fat will dissolve in the alcohol)Filter off the ethanolpour the ethanol into waterA milky emulsion will form if fat was present(fat can no longer dissolve and forms small droplets
68 Proteins(Polypeptides) Proteins make up more than 50% of the dry mass of cellsThey have many important functionsAll proteins are made up of amino acidsFunctions of proteins
69 active transportchannel proteinRespiration/ photosynthesiscomplexintracellular (metabolic)glycoproteinmembraneenzymesExtracellular (digestive)Albumin/ globulinbloodglobulartransportantibodieshaemoglobinProteins in living organismshormonescollagenfibrouscontractilestructuralelastinbloodActin/myosin (muscles)Fibrinogen (fibrin)keratin
71 Amino Acid Structure NH2 is the a amine or amino group COOH is the carboxylic acid groupThe R group or amino acid side chain varies.There are 20 different R groups found in nature so giving 20 different naturally occuring amino acids
72 The 20 naturally occurring amino acids R groups
77 Polypeptide formation Adding more amino acids to the chain forms a polypeptideIn cells this occurs in ribosomesA protein molecule may contain many hundred AAs and sometimes more than one polypeptide chain
78 Protein – Primary structure The sequence of the amino acids in the polypeptide is known as its primary structureA protein of several hundred amino acids has a huge number of possible primary structuresA change in one of the AAs can completely alter the properties of the protein
79 Protein- Secondary Structure This is when parts of the polypeptide chain becomes twisted or foldedThere are 2 main types of 2° structure: helix pleated sheet
80 Polypeptide α helixProteins form this stable helix due to hydrogen bondingThis takes place between –C=O of one A.AAnd the –N-H of the A.A 4 places ahead
81 Polypeptide - β Pleated Sheet This looser, straighter shape is also formed by H bonds.This time between –C=O and –N-H of adjacent chains
82 Proteins may contain both of these secondary structures They are easily disrupted by heat & changes in pH
83 Biological molecules chemical tests Reducing SugarsHeat the sugar solution with an equal volume of blue benedict's solution for 2-3 minutes at about 90°CA positive result is a brick red precipitateNon reducing sugar (sucrose)Collect some filtrate from the reducing sugar testAdd a few drops of acid and heat in a water bath for a few minutesNeutralise with an equal amount of sodium hydroxide solutionRepeat the benedicts test, a brick red ppt is a positive resultStarchAdd orange brown iodine solution to the materialA blue black colour is produced on contact with starchProteinBiuret reagent is made by combining equal amounts of Sodium Hydroxide and Copper SulphateAdd biuret reagent to the suspect food or add some dilute sodium hydroxide solution and mix followed by a little dilute copper sulphate solution.The copper ions interact with the amino groups in the protein to give PURPLE colour for a positive resultIf the solution stays BLUE this is a negative result
84 Food Testing Starch Add orange brown iodine solution to the material A blue black colour is produced on contact with starchProteinBiuret reagent is made by combining equal amounts of Sodium Hydroxide and Copper SulphateAdd biuret reagent to the suspect food or add some dilute sodium hydroxide solution and mix followed by a little dilute copper sulphate solution.The copper ions interact with the amino groups in the protein to give PURPLE colour for a positive resultIf the solution stays BLUE this is a negative result
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