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18 Cards in this Set
- Front
- Back
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what is the structure of an amino acid? |
amino group -NH2 Carboxyl group -COOH hydrogen atom - H R group - a variety of different chemical groups that give different amino acids |
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how do polypeptides form? |
. amino acids are linked together by peptide bonds formed in condensation reactions . this forms polypeptides (polymerisation) . the reverse reaction occurs during digestion, hydrolysis . there are 20 naturally occurring amino acids . allows a limitless amount of combination |
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describe the primary structure of proteins |
. sequence of amino acids in a polypeptide chain . determines the ultimate make up of the protein . hence shape and function (which are very specific) |
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describe the secondary structure of proteins |
. weak hydrogen bonds form readily between the poly peoptide to form either . a twisted 3-D alpha helix . beta pleat |
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describe the tertiary structure of proteins |
. the alpha helix's can be twisted and folded even more . disulphide bonds - fairly strong, not easily broken . ionic bonds - weaker than disulphide bonds and easily broke by a change in pH . hydrogen bonds - numerous, but easily broken |
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describe the quaternary structure of proteins |
. contain a number of polypeptide chains all linked together e.g. haemoglobin . often contain prosthetic groups |
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what is the test for proteins? |
. Buiret test . place sample of solution to be tested in test tube add equal volume of sodium hydroxide . add few drops of copper (II) sulphate solution and mix gently . purple colouration shows presence of peptide bonds . if no protein is present, solution stays blue |
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what are enzymes? |
. enzymes are biological catalysts that speed up a reaction, and lower the activation energy without being used up . they have an active site which is where their substrate binds to |
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how doe enzymes speed up reactions? |
. in a chemical reaction an activation energy needs to be met to start the reaction . enzymes reduce this activation energy needed in a reaction to make it easier and faster rate f reaction . enzyme substrate complex is what lowers the activation energy . if two substrates need to be formed,mthe enzyme can hold them close together, reducing any repulsion . if the enzyme is catalysing a break down, fitting into the active site puts a stain on the bonds to break the substrate up . |
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describe the lock and key model
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. substrate fits the enzyme the same way a key fits a lock . therefore have a complementary shape . scientists soon realised this was wrong and came up with the induced it model |
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describe the induced fir model |
. the substrate doesn't only need to be complimentary to the active site it needs to change the enzymes shape in the right way in order to fit as well . this places a strain on the substate making, hence lowering the activation energy |
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what are the main factors affecting the rate of enzyme action? |
. temperature . concentration of substate and enzyme . pH |
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what are the two ways you can measure an enzymes activity? |
. measuring the amount of product produced . measuring the amount of substrate left |
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what is the effect of temperature on enzyme action? |
. reaction increases as temperature increases . more heat - more kinetic energy - more collisions - higher the energy of the collisions - more likely to collide with enzyme active site - each collision is more likely to end up in a reaction . if the temperature gets too high bonds in the enzymes protein structure break and the enzyme will denature permanently . all enzymes have an optimum temperature |
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what is the effect of pH on enzyme action? |
. all enzymes have an optimum pH . above and below optimum pH the OH- and the H+ ions disrupt the enzymes proteins structure (break bonds) and denature it . active site changes shape and enzyme no longer works |
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what is the effect of substate concentration on enzyme action? |
. the higher the substrate concentration the faster the reaction - up until a saturation point where there are not enough active sites to fill up all the substrate . adding more will make no difference unless you add more enzyme |
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what is a competitive inhibitor? |
. similar shape to that of the active site . they can block the active site impermanently or permanently . they compete with the substrate molecules to bind to the active site but no reaction takes place . if there is a high concentration of the inhibitor it will most probably stop most reactions from taking place |
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what is a non competitive inhibitor? |
. molecules that bind to the enzyme other than the active site . this changes the active sites shape so that no substrate can bind . this can be impermanent or permanent . they don't compete with the substrate because they are a different shape . increasing substate won't make any difference, enzyme activity will still be inhibited |
