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| Frage | Antworten |
| Structure of an amino acid | |
| Primary Structure | The sequence of amino acids in a protein molecule |
| Secondary structure | Coiling or folding of the chain due to formation of hydrogen bonds. Alpha-helix and Beta-pleated sheet |
| Tertiary Structure | Overall 3D structure of the molecule. Formation of hydrogen bonds, disulphide bridges and hydrophobic & hydrophillic interactions |
| Quarternary structure | Protein structure where it consists of more than 1 polypeptide chain. E.g Haemoglobin has 4 polypeptide chains |
| Structure of a collagen molecule | - 3 polypeptide chains ( 3 syllables=3 chains) - 1000 amino acids long - Hydrogen and covalent bonds form - Cross links are staggered for strength |
| Structure of haemoglobin | - Globular protein -Soluble in water -Wide range of amino acids -Contains 4 haem groups with Fe+ ions -Alpha helix |
| Structural difference between alpha and beta glucose | In alpha glucose the OH group on carbon 1 is above the plane of the ring. In beta glucose the OH group on carbon 1 is below the plane of the ring. |
| Structure of starch (amylase) | -Made of alpha glucose - Straight chain - tends to coil up |
| Structure of cellulose | -Made of beta glucose, in a chain alternate glucose subunits are inverted -Forms straight chains -Forms plant cell walls - The beta-glycosidic bonds can only be broken by a cellulose enzyme (humans don't have this) |
| Structure of glycogen | - Mostly like amylase - many 1-4 glycosidic bonds - 9% 1-6 branches |
| Structure of a triglyceride | - Glycerol and 3 fatty acids -Insoluble in water does not affect cell water potential -Compact energy store |
| Structure of a phospholipid | -Glycerol plus 2 fatty acids and a phosphate group -Part hydrophobic, part hydrophillic (ideal for cell surface membranes) |
| Cholesterol | -Small, thin molecule -Fit into the lipid bilayer giving strength and stability |
| Chemical test for protein - Biuret test | If a protein is present the solution changes colour from pale blue to lilac |
| Chemical test for reducing sugars -Benedict's test | Add benedict's solution, heat to 80 degrees, if a reducing sugar is present the mixture will change colour from blue to orange/red |
| Chemical test for non-reducing sugars -benedict's test | If the reducing test is negative, boil with hydrochloric acid, cool and neutralise with sodium hydrogencarbonate and repeat benedict's test |
| Chemical test for starch -Iodine solution | Colour changes from yellow to blue/black if starch is present |
| Chemical tests for lipids -emulsion test | Mix with ethanol, pour into water, if an emulsion forms then a lipid is present |
| How the concentration of glucose can be determined by colorimetry | -Benedict's test reveals reducing sugars (if there is an orange/brown precipitate) -The more reducing sugar present the more precipitate will form and the more benedicts solution used up. -Once precipitate has been filtered out, the concentration of remaining solution can be measured -This tells you how much benedicts was used up and can be used to estimate the the concentration of reducing sugar in original sample |
| Preparing a calibration curve | - Zero the device using a blank (water) - Take a range of known concentrations of reducing sugars -carry out benedicts test on each and filter out precipitate -Use a colorimeter to get readings of the amount light passing through the solutions -Plot the readings on a graph to show %transmission against concentration -Measure the %transmission of the unknown in the colorimeter -Use this to read the equivalent reducing sugar concentration from %transmission |
| Deoxyribonucleic acid (DNA) | -Is a polynucleotide -Usually double stranded -Made up of nucleotides containing the bases Adenine (A), Thymine (T), Guanine (G), Cytosine (C) |
| Ribonucleic acid (RNA) | -Is a polynucleotide -Usually single stranded - Made up of nucelotides containing the bases Adenine (A), Uracil (U), Cytosine (C), Guanine (G) |
| DNA replication | -Double helix is untwisted - DNA 'unzipped' and hydrogen bonds between bases are broken -Free DNA nucleotides are H-bonded onto their exposed complementary bases -DNA polymerase catalyses formation of covalent bonds between phosphates and sugars -This continues till there are 2 identical strands -These are then 'proof read' by DNA polymerase to prevent mistakes |
| Gene | A gene is a sequence of DNA nucelotides that code for a polypeptide |
| Protein Synthesis | -Required gene exposed by splitting H-bonds holding the helix together in the region - RNA nucleotides form a complementary strand (mRNA) which is a copy of the coding strand -mRNA peels off DNA and leaves via nuclear pores -mRNA attaches to a ribosome -tRNA molecules bring amino acids to the ribosome in the correct order according to base sequence on the mRNA -Amino acids are joined together by peptide bonds to form a protein with a specific tertiary structure |
| Enzymes | -Globular Proteins -Specific tertiary structure -Catalyse metabolic reactions in living organisms -Can be intracellular or extracellular |
| Enzyme specificity | The active site is a specific shape depending on the reaction it catalyses, meaning that other molecules wont fit the active site. |
| Lock and Key hypothesis | The theory of enzyme action in which the enzyme active site is complementary to the substrate molecule |
| Induced fit hypothesis | The theory of enzyme action in which the enzyme active site changes shape to fit the substrate molecule more closely as it binds. |
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