811086
Description
Flashcards by Hannah Tribe, updated more than 1 year ago
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Created by Hannah Tribe
almost 10 years ago
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| Question | Answer |
| Name 5 functions of enzymes | 1. Digestion 2. Ion pumps 3. Haemostasis 4. Complement activation 5. Movement |
| What is the Vmax and how is it achieved? | The maximum velocity a reaction can reach. Achieved when all the enzyme-substrate complexes are full. |
| What is the Michaelis constant (Km) and how is it achieved? | The concentration of the substrate when the velocity of the reaction is at 50% maximum. Achieved when half of the active sites are full. |
| The binding of enzyme with substrate is limited by _________ and cannot really be changed by evolution. | diffusion |
| The conversion of the enzyme-substrate complex to the product can be improved by evolution. The _______ of the enzyme can be changed to improve conversion to products. | structure |
| What is a 'perfect' enzyme? | An enzyme whose activity is limited solely by diffusion |
| When an enzyme is 'perfect', the reaction is said to be _________ ________. The rate of these reactions is approx. ____^__ M-1 s-1. | diffusion controlled, 10^8 |
| How can the rate of the reaction be calculated using the Michaelis-Menten kinetics? | rate = k3/Km |
| How can k3 be calculated? | k3 = Vmax/enzyme concentration |
| Name 1 enzyme which is near 'perfect' | Carbonic anhydrase |
| How can it be tested experimentally to see if an enzyme is 'perfect'? Which enzyme was this first tested on? | Measure the free energy of activation at each stage of the reaction. First tested on Triosephosphate isomerase. |
| What do serine proteases do and why are they so efficient? | Hydrolyse peptide bonds. The active site contains a very reactive serine residue. |
| Name 3 serine proteases and where they are produced | 1. Chymotrypsin - pancreas 2. Trypsin - pancreas 3. Elastase - lungs |
| What do they all have at their active site, which is responsible for the reactive serine residue? | 'Catalytic triad' (Histidine, Aspartate and Serine) |
| How is this enzyme pathway different to the uncatalysed pathway? | The enzyme (specifically the nucleophilic serine) binds to part of the protein and forms an acyl-enzyme. The ester bond here is easier to hydrolyse than amides, so acyl-enzyme is hydrolysed to give enzyme + product. |
| Chymotrypsin can only cleave to bonds following __________ side chains (e.g. Phenylalanine, Tryptophan, Tyrosine). | hydrophobic |
| Trypsin can only cleave to bonds following _________ chains (e.g. Lysine, Arginine). | positive |
| Elastase can only cleave to bonds following _____ side chains. | small |
| Name 2 molecular machines | 1. ATP synthase 2. Topoisomerases |
| How does ATP synthase work? | Embedded in the inner mitochondrial membrane, protons flow through it and the proton gradient causes the spindle to rotate. The spindle has 3 binding sites and as it rotates, ADP+Pi enters one site and ATP is released from another. |
| How does topoisomerase II work? | It untangles chromosomes using ATP. The 1st DNA strand binds to a 'gate' on the enzyme. ATP binds to another 'gate'. 2nd DNA strand enters and ATP gate closes around it. The 1st strand is cut to allow 2nd to pass through it, then 1st is resealed again. |
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