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Carbohydrates Condensation & Hydrolysis Reaction Condensation Reaction Condensation is a chemical reaction whereby 2 simple molecules are joined together to form a larger molecule with the removal of 1 molecule of water Hydrolysis/ Hydrolytic Reaction Reaction where a water molecule is added to split complex sugar into simpler component molecules by - Heating with dilute acids at 100°C (chemical method) - Treating with suitable enzyme at room temperature/ optimum temperature of the enzyme (enzymatic method) Function General uses of monosaccharides and disaccharides Building blocks for larger molecules (e.g. DNA, cellulose, starch, glycogen) Source of respiratory energy (glucose) Transport compound (sucrose in plant phloem) Infant milk (lactose) Attraction – flower nectuary, fruit (fructose) Honey – Bees food storage General uses of polysaccharides Polysaccharides are many monosaccharides linked by glycosidic bonds Examples – starch, glycogen, cellulose Energy Storage - starch (plant) and glycogen (animal) Structural - Cellulose cell wall (plant) and Chitin (insects/crab/shrimp) Contain the elements C, H, O They are either made from single monosaccharide monomers or from several monosaccharides joined together Classified as: Monosaccharides eg glucose, fructose, galactose Disaccharides eg sucrose, maltose, lactose Polysaccharides eg cellulose, glycogen, starch Other polysaccharides and polysaccharide derivatives eg pectins, chitin and mucopolysaccharides Many monosaccharides are joined in a chain to form polysaccharides. Glycogen and starch are storage carbohydrates in animals and plants respectively. Monosaccharides Trioses – C3H6O3 e.g. glyceraldehyde Pentoses – C5H10O5 e.g. deoxyribose Hexoses – C6H12O6 e.g. glucose, fructose General Formula: (CH2O)n Monosaccharides differ ONLY in terms of the details of arrangement of atoms within a molecule, which gives them their different chemical and biological properties Hence, they show isomerism Isomers have different structural formulae but same molecular formula Types of isomers: aldose and ketose, open-chain and ring forms, alpha and beta Disaccharides Made by combining 2 monosaccharides together This is a condensation reaction producing a glycosidic bond (broken by hydrolysis) Disaccharides made from hexoses have the formula C12H22O11 Examples – sucrose (glucose + fructose), maltose (glucose + glucose) Starch and Glycogen (energy stores) Their molecules have many side branches where glucose molecules can be removed from their tips (by enzymes) Their insolubility stops them interfering with osmosis Their compactness provides an efficient way to store lots of glucose for future cellular respiration Cellulose Made from long, straight chains of glucose Chains cross-linked by H-bonds which holds them tightly together (excludes water) Chemically very inert and insoluble – few ‘tips’ on molecule make it difficult to digest Many molecules form strong fibrils Only some bacteria, fungi and a very small number of animals can secrete cellulase enzymes Proteins Sensitive to pH and heat Shape determines its function Special group of proteins are enzymes Basic unit of proteins Amino acids 20 essential amino acids for protein formation Protein Structures Primary o Order in which amino acids are linked to form a polypeptide chain o Individual amino acids join to form primary structure Secondary o Way the polypeptide chain is coiled and folded, alpha-helix and beta-pleated o Helix or sheet Tertiary o Large globular proteins formed by the coiling and folding the already coiled and folded chain eg enzymes o 3 dimensional Quaternary o Proteins made from 2 more polypeptides eg haemoglobin Structural classification Fibrous proteins Properties: Water insoluble Very touch physically; may be supple or stretchy Parallel polypeptide chains in long fibres or sheets Function: Structural role in cells and organisms (eg collagen found in connective tissue, cartilage, bones, tendons, blood vessel walls) Contractile (eg myosin, actin) Collagen consists of 3 helical polypeptides wound around each other to form a ‘rope’. Every 3rd amino acid in each polypeptide is a glycine molecule where hydrogen bonding occurs, holding the 3 strands together Globular proteins Properties: Water soluble Tertiary structure critical to function Polypeptide chains folded into a spherical shape Function: Catalytic (eg enzymes) Regulatory (eg hormones, insulin) Transport (eg haemoglobin) Protective (eg antibodies) Bovine insulin is a relatively small protein consisting of 2 polypeptide chains. These 2 chains are held together by disulfide bridges between neighbouring cysteine molecules. Denaturation of Proteins Loss of 3D structure and biological function Often permanent Results from alteration of bonds that maintain secondary and tertiary structure of protein Amino acid sequence remains unchanged Agents that cause denaturation: o Strong acids and alkalis: disrupt ionic bonds, result in coagulation of protein o Heavy metals: disrupt ionic bonds, reduce protein charge, causes precipitation of protein o Heat and radiation: cause disruption of bonds in protein through increased energy o Detergents and solvents: form bonds with non-polar groups in protein, disrupting hydrogen bonding Fats Function Mammals Water repellent properties – waterproof fur and skin. Structural – Cell membranes, phospholipids and polar nature Electrical insulation – myelin, insulates neurones, impulse transmission more rapid. Hormones – steroids e.g. testosterone and oestrogen Physical protection – shock absorb, found round delicate organs e.g. kidneys Thermal insulation – conducts heat poorly, so insulates. Blubber in diving animals. Energy storage – yield twice as much energy compared with carbohydrates Plants Attraction – plant scents contain fatty acids Waterproofing – wax for the cuticle (not glycerol, different alcohol used) Energy storage – Oil droplets in plant cells Other Honey comb – Bees wax Properties Forms: oil, wax, fat Insoluble Water- repelling Are usually insoluble in water, but soluble in organic solvents. Contain C, H and O. (CH3(CH2)nCOOH) Less oxygen than carbohydrates Identified using the emulsion test. Triglycerides (fats & oils) These are NOT made from monomers Each contains 1 glycerol and 3 fatty acid molecules (elements: C, H, O) They are linked by ester bonds These form during condensation reactions Fats (solid) contain saturated fatty acid chains, oils (liquid) have unsaturated chains Triglycerides (fats) are formed using ester bonds Saturated and Unsaturated Saturated fatty acid e.g. Stearic acid More hydrogen atoms No double bonds No kinks Unsaturated fatty acid e.g. Oleic acid Less hydrogen atoms Have double bonds Have kinks Phospholipids Consist of organic group, phosphate group, glycerol and fatty acid Bonds between the glycerol and fatty acid are broken by hydrolysis Major component of the plasma membrane, because they have a hydrophilic head and hydrophobic tail (polar molecules), which form a bilayer Heads outside, tails inside One fatty acid in triglyceride swapped for phosphate base Water Inorganic molecules Polar molecules Environment in which metabolic reactions can occur Water takes part in, and is a common product of many reactions Dipole nature Small positive charge on each of the two hydrogens and a small negative charge on the oxygen Attracted to each other, creating hydrogen bonds Strong bonds determine almost every physical property of water and many of its chemical properties Thermal properties Absorbs or releases more heat than many substances for each degree of temperature increase or decrease Widely used for cooling/transferring heat in thermal and chemical processes Evaporation of water in sweat or in transpiration causes marked cooling Much heat is lost by the evaporation of a small quantity of water Contents of cells and aquatic environments are slow to freeze in cold water Colourless Plants can photosynthesize at depth in water Light can penetrate deeply into living tissues Surface tension Measure of strength of water’s surface film Attraction between water molecules creates strong film Permits water to hold up substances heavier and denser than itself High surface tension Sticky and elastic Hydrogen atoms are “attached” to one side of the oxygen atom, so it has a positive charge on the side (hydrogen) and a negative charge on the other side (oxygen) Since opposite electrical charges attract, water molecules tend to attract each other Small animals can land on and move over surface of water Water forms droplets on surfaces and runs off Molecules in motion Surface tension is responsible for capillary action Allows water (and dissolved substances) to move through roots of plants and through blood vessels in our bodies Water molecules also bind to other substances – adhesion For example, in a thin glass tube, when the molecules at the edge adhere to the molecules of glass just above them, they also tow other water molecules along with them. The water surface pulls the entire body of water to a new level until the downward force of gravity is too great to be overcome. Capillary action: movement of water within spaces of a porous material, due to the forces of adhesion, cohesion and surface tension Can move through extremely narrow spaces (eg between soil particles, and in cell walls) Water column does not break or pull apart under tension Plants and trees need capillary action to transport water from roots to leaves Universal solvent Ability to dissolve other substances Transfers nutrients vital to life in animals and plants Medium for chemical reactions of life Boiling and freezing point Freezes at 0 oC and boils at 100 oC Solid form (ice) is less dense than liquid form, which is why ice floats Ice forms on surface of water, insulating water below When surface water does freeze, aquatic life can survive below the ice Liquid at room temperature: liquid medium for living things Neutral pH of 7 Not acidic nor basic Pure water Specific heat index High specific heat index: Can absorb a lot of heat before it begins to get hot Valuable to industries as a coolant Regulate rate at which air changes temperature, which is why temperature change between seasons is gradual rather than sudden (especially near oceans) Bulky organisms have a stable temperature in the face of fluctuating external temperatures Viscosity Resistance to internal friction between molecules Water has low viscosity (vs honey, shampoo) Affected by temperature At higher temp, viscosity decreases as the molecules take on more kinetic energy, allowing them to move past each other faster Flows readily through narrow capillaries Vital Minerals Mineral Calcium Phosphorus Iron Function Formation of bones and teeth Blood clotting Normal muscle and nerve activity Formation of bones and teeth Regulation of blood pH, muscle contraction and nerve activity Component of enzymes, DNA, RNA, ATP Component of haemoglobin (carries oxygen to body cells) and cytochromes (ATP formation) Iodine Part of thyroid hormone, required by thyroid gland Sodium Regulation of body fluid pH Transmission of nerve impulses Transmission of nerve impulses Muscle contraction Involved in controlling plant water balance Muscle and nerve function Bone formation Enzyme function Component of chlorophyll Tooth structure Enzyme activator for carbohydrate, protein and fat metabolism Important in growth of cartilage and bone tissue Ingredient in several respiratory enzymes Needed for development of red blood cells Component of insulin Builds hair, nails, skin Potassium Magnesium Fluorine Manganese Copper Sulphur Inorganic ions Important for structure and metabolism of all living organisms Ion = atom that has gained or lost one or more electrons Usually soluble in water Source Milk, cheese, nuts, whole grains Milk, whole-grain cereals, meat, vegetables Liver, egg yolk, pease, enriched cereals, whole grains, meat, raisins, leafy vegetables Seafood, eggs, milk, iodized table salt Bacon, butter, table salt, vegetables Vegetables, bananas, ketchup Potatoes, fruits, whole-grain cereals, vegetables Fluoridated water Wheat germ, nuts, bran, leafy green vegetables Kidney, liver, beans, wholemeal flour, lentils Nuts, dried fruits, barley, oatmeal, eggs, beans, cheese