Biological Molecules

Monomers and Polymers Condensation reactions Join monomers together into larger molecules, releasing water Monosaccharides → Disaccharides → Polysaccharides: glycosidic bonds formed Amino acids → Polypeptides: peptide bond Glycerol + fatty acids → Triglycerides: ester bonds Carbohydrates Made up of monosaccharides (monomers of carbohydrates) Common monosaccharides - glucose, galactose, fructose Disaccharides Formed by condensation reaction of 2 monosaccharides Maltose → Glucose + Glucose Sucrose → Glucose + Fructose Lactose → Glucose + Galactose thumb|α-glucose form, with the -OH group on the right-most carbon pointing down Glucose Two isomers: α-glucose: Carbon atom 1 has hydrogen pointing up, and hydroxyl group pointing down β-glucose: Carbon atom 1 has hydrogen and hydroxyl groups flipped thumb|β-glucose, showing the right-most -OH group pointing up The acronyms 'ADDUD' and 'BUDUD' can be used to remember which way the -OH groups point. ADDUD - α-glucose, down, down, up, down. BUDUD - β-glucose, up, down, up down. Polysaccharides Formed by condensation of many monosaccharides Glycogen → condensation of α-glucose Starch → condensation of α-glucose Cellulose → condensation of β-glucose Structure of Glycogen Energy store in animals Highly branched structure, coiled – so compact Unable to diffuse out of cells, so stays where it is needed until energy is required Structure of Cellulose Unbranched, linear chains Used in plant cell wall – provides rigidity to plantsthumb|466x466px|The structures of starch, glycogen, and cellulose. The way the molecules pack together can be seen, with all molecules in cellulose being parallel and tightly packed. The starch and glycogen molecules have a much more branched structure, causing less tight packing Fibres group together to form microfibrils – hydrogen bonds (strength in large numbers) Structure of Starch Forms granules – unable to move out of cells it is formed in – doesn’t have to diffuse far, so reasonably quick access to energy Branched chains, coiled – compact Lipids Triglycerides Glycerol + 3 fatty acid tails Form oils, waxes, fats Hydrophobic – do not mix with water thumb|Molecular structure of a triglyceride Phospholipids Form the cell wall – phospholipid bilayer Phosphate + glycerol + 2 fatty acid tails Polar molecules – phosphate head is hydrophilic (water loving) // fatty acid tails are hydrophobic (water hating) thumb|Molecular structure of a phospholipid Fatty acids Saturated – all carbon atoms have single bonds – with the maximum number of hydrogens possible Unsaturated Monounsaturated – 1 pair of carbon atoms have a double bond; removes 2 hydrogens, causes a kink in the chain Polyunsaturated – More than 1 pair of carbon atoms have a double bond; removes more than 2 hydrogens, causes many kinks in the chain Have less energy content than unsaturated fatty acids left|thumb|599x599px|A polyunsaturated fatty acid Proteins Made up of amino acids thumb|301x301px|General structure of an amino acid, the monomer of a protein (polypeptide) Amine group: NH2 Carboxyl group: COOH R group – the side chain causing the amino acid to be unique Dipeptides – condensation of two amino acids Polypeptides – condensation of many amino acids Proteins can be made up of multiple polypeptide chains Primary structure: order of amino acids – polypeptide chain Secondary structure: α-helix or β-pleated sheet – formed by hydrogen bonds between R-groups Tertiary structure: further coiling of α-helix / β-pleated sheet – more compact Quaternary structure: linking together of multiple tertiary structure polypeptide chains Hydrogen bonds – hold together the polypeptide chains in quaternary structure Ionic bonds – join together amino acids into polypeptide chain Disulphide bridges – strong bonds between R-groups holding α-helix / β-pleated sheet togetherthumb|597x597px|The four structures a protein can be in|center Enzymes Lower the activation energy of the reaction it catalyses Lock and Key model of enzyme action Substrate fits perfectly in the enzyme No explanation as to how the enzyme catalyses the reaction Induced Fit model of enzyme action Enzyme active site changes shape slightly to allow the substrate to bind to it Active site puts stresses on the substrate, causing bonds to brake Reaction is catalysed, causing the product(s) to be released Enzymes are only able to have 1 substrate fit it – amylase only catalyses starch hydrolysis Enzyme concentration – a higher concentration will cause the substrate to be broken down faster. The rate of reaction will plateau as the substrate concentration decreases, as collisions are less likely to occur Substrate concentration – higher concentration of substrate means that the enzymes are more likely to collide with substrate. Increase rate of reaction, to a point. Once all of the enzyme has substrate in active site, reaction cannot continue furtherthumb|289x289px|Competitive and non-competitive inhibitors Inhibitor concentration – higher concentration of competitive inhibitors will cause reaction to slow, as more competitive inhibitor blocks active sites Non-competitive inhibitors will have an impact, however it is not based on concentration as they do not block the active site pH – outside of the enzymes optimum pH, the active site denatures quickly. This prevents the reaction from being catalysed Temperature – below the optimum temperature, the reaction slows, as less energy to cause collisions Above optimum temp – reaction stops – enzymes denaturethumb|285x285px|Enzyme activity at differing temperatures|nonethumb|289x289px|Enzyme activity at differing pH's|none Nucleic Acids thumb|The double helix of DNA Genetic material for living organisms Adenine (purine), Thymine / Uracil (pyramidal), Guanine (purine), Cytosine (pyramidal)left|thumb|Semi-conservative replication: the purple strands are the original, and the orange strands are new Semi-Conservative Replication DNA unzips: DNA Helicase Base pairs move in between the unzipped strands DNA Polymerase used to bind the new bases to the old strands Forms 2 DNA strands, each with 1 old strand and 1 new strand Proof for semi-conservative replication DNA replicated until all Nitrogen is 15N – this is heavier, causing the strand to be lower in solution DNA then replicated 1 generation with 14N – this creates a hybrid DNA, with 50% 15N and 50% 14N DNA replicated 1 further generation in 14N solution – creating DNA with 25% 15N and 75% 14N This is repeated, eventually forming DNA only containing 14N The solution can be centrifuged, DNA containing different Nitrogen isotopes to be identified ATP – Adenosine Triphosphate thumb|338x338px|ATP, the base (adenosine) is circled in red Used to transfer energy within cells Made of: Adenine, 3× Phosphate groups, Ribose sugar – condensation on ATP, forming ADP and a phosphate group; breaking the bond releases energy Low activation energy, so it is easy to release energy ATPase – enzyme catalysing hydrolysis of ATP (break down of ATP into ADP) Photophosphorylation Photosynthesis: Plants only, Using light to synthesise ADP → ATP Oxidative Phosphorylation Using respiration to synthesise ADP → ATP; Plants and Animals Substrate-level Phosphorylation When phosphate groups are transferred from donors; plants and animals Uses of ATP Metabolic Processes – provides energy to build up molecules from subunits Movement – energy is required for muscular contraction Active Transport – movement of molecules against a concentration gradient Secretion – ATP is needed to form lysosomes to encase cell products Activation of Molecules – inorganic phosphate released in hydrolysis of ATP can phosphorylate other molecules Water thumb|352x352px|A diagram of water molecules, showing the more negative and more positive ends interacting through a hydrogen bond Essential for all living organisms Polar Molecule Hydrogen bonds between water molecules require lots of energy to break Causes water to have a high surface tension Solvent As water is polar, other polar molecules are able to dissolve in it Ionic compounds are surrounded by water molecules when dissolved Allows gases to be dissolved – CO2, O2, NH3… High Specific Heat Capacity A lot of energy is required to increase the temperature by 1° - this is due to the strength of the hydrogen bonds This means that water acts as a buffer, reducing temperature fluctuations High Latent Heat of Vaporisation A lot of energy is required to evaporate water (into steam) Ideal for cooling an organism – sweating (animals) or transpiring (plants) Cohesion between Molecules High surface tension means that column of water is able to be pulled up a vessel (such as a xylem) Metabolite Used in condensation / hydrolysis reactions to break / form bonds Inorganic Ions Occur in solution in the cytoplasm / bodily fluids Some are in high concentrations, others in low concentrations Each ion has a specific role Iron ions Haemoglobin Sodium ions co-transport of Glucose and Amino Acids Phosphate ions Part of DNA and ATP Testing for Substances Biology Chemistry