Enzymes Flashcards
<p>What are ribozymes?</p>
<p>Catalytic RNA molecules with no protein component</p>
<p>What is a cofactor?</p>
<p>A non-protein component needed for activity, usually metal ions</p>
<p>What is a co-enzyme?</p>
<p>A complex organic molecule, usually produced from a vitaminFADNAD+</p>
<p>What is a prosthetic group?</p>
<p>A non-protein group forming part of or combined with a protein.</p>
<p>i.e - A cofactor covalently bound to an enzyme or very tightly associated with an enzyme</p>
<p>What is an apoenzyme?</p>
<p>An inactive enzyme, activation of the enzyme occurs upon binding of an organic or inorganic cofactor.</p>
<p>What is a holoenzyme?</p>
<p>WHole enzyme, the apoenzyme plus the cofactor</p>
<p>Why isn't a spontaneous reaction instantaneous?</p>
<p>Because of the activation energy barrier</p>
<p>What is the activation energy used for?</p>
<p>Positioning chemical groups correctly</p>
<p>What is the transition state?</p>
<p>The moment that chemical bonds are formed and brokenThe reaction from this point could then go to products or reactants</p>
<p>What type of bonds occur between substrate and enzyme?</p>
<p>Non-covalent</p>
<p>What is the active site complementary to?</p>
<p>The transition state </p>
<p>How do enzymes reduce activation energy?</p>
<p>Entropy reductionDesolvation Induced fit</p>
<p>How does entropy reduction reduce activation energy?</p>
<p>Molecules react by bumping into each other, enzymes orientate the substrates improving the chance of a successful collision and a resulting reaction</p>
<p>How does desolvation decrease the activation energy?</p>
<p>H bonds with the substrate and the solution are replaced by the weak bonds between the substrate and the enzyme.</p>
<p>How does induced fit decrease activation energy?</p>
<p>Conformational changes occur in the protein structure when the substrate binds</p>
<p>Which part of an enzyme reaction occurs more slowly?</p>
<p>The second part of the equation, producing E and P from the enzyme substrate complex</p>
<p>Which stage of an enzyme reaction is reversible?</p>
<p>The formation of ES from E and SK1 denotes the forward reactionK-1 denotes the reverse reaction</p>
<p>What is Km?</p>
<p>It is the substrate concentration when the reaction velocity is exactly half of the max velocity</p>
<p>On a lineweaver burke plot what does the y intercept represent?</p>
<p>1/VMax</p>
<p>On a lineweaver burke plot what does the X intercept represent?</p>
<p>1/Km</p>
<p>What does Km measure?</p>
<p>The ration of rate constant for breakdown of ES to E+S compared to the rate constant for formation of ES from E+SIt gives you a clue to the affinity of the enzyme with it's substrate</p>
<p>What does a large Km value indicate?</p>
<p>Less stable ES complex</p>
<p>Which enzyme activity fluctuates directly with blood glucose intake?</p>
<p>Glucokinase Catalyses Glucose + ATP to glucose - 6 - phosphate</p>
<p>What is used to determine normal enzyme activity?</p>
<p>Arbitrary values such as 1U/ml or 100%</p>
<p>How are enzymes separated?</p>
<p>Gel electrophoresis</p>
<p>Where can you find creatine kinase?</p>
<p>In the heartElevation of plasma CK2 is diagnostic for myocardial infarction</p>
<p>What are the possible reaction mechanisms for enzymes with two or more substrates</p>
<p>Random or ordered with a ternary complexNo ternary complex formation</p>
<p>Describe the reaction involving a ternary complex<br></br>Random order</p>
<p>Can bind to either substrate first</p>
<p>Eventually complexes with both substrates</p>
<p>Forms two products</p>
<p>Describe the reaction involving a ternary complex<br></br>Ordered</p>
<p>Attaches to one substrate first, it is the fed the other substrate</p>
<p>Describe the reaction with no ternary complex formed</p>
<p>Reaction occurs with enzyme and substrate producing altered enzyme and a product</p>
<p></p>
<p>Second reaction occurs with the altered enzyme and the second substrate, producing a second product</p>
<p>What type of reactions have no ternary complex formation?</p>
<p>Transamination reactions</p>
<p>How does temperature affect the function of an enzyme?</p>
<p>Increase temperature will increase molecule collisions and it will increases the internal energy of molecules</p>
<p></p>
<p>Eventually denautres the enzyme</p>
<p>How does pH alter the function of an enzyme?</p>
<p>pH changes the charge of an amino acid, can stop the active site functioning if the amino acids in the active sites change charge.</p>
<p></p>
<p>Extreme pH will denature the enzyme</p>
<p></p>
<p>pH will affect the substrates</p>
<p>What effect does a competetive inhibitor have on the Vmax and Km?</p>
<p>Same Vmax</p>
<p>Km increases (since affinity active site has for the enzyme substrate complex decreases)</p>
<p>What is an example of a transition state anologue?</p>
<p>Oseltamavir</p>
<p>What does a catalytic antibody resemble?</p>
<p>It resembles the active site of the original enzyme, since it is specific to a transition state molecule</p>
<p>What effect do non-competitive inhibitors have on the Vmax and the Km values?</p>
<p>V max will decrease - inhibition remains the same regrdless of the change in substrate concentration</p>
<p>Km remains the same as the substrate is still able to bind to the active site</p>
<p>Which type of inhibitors bind in an rreversible manner?</p>
<p>Those that bind in a covalent manner</p>
<p>Which enzyme in a pathway holds the regulatory step for that pathway?</p>
<p>Often the first one in the pathway</p>
<p>What are the regulatory types of enzymes called?</p>
<p>Allosteric enzymes and covalently modified enzymes</p>
<p>What is feedback inhibition?</p>
<p>When there is a build up of an end product in a pathway or a key junction in a pathway that ultimately slows down the entire pathway</p>
<p>How is the change in the structure of an enzyme brought about in allosteric control?</p>
<p>An allosteric effector (usually a metabolite) binds non-covalently to a site on the enzyme that is not the active site, changing the enzymes structure</p>
<p>What are the two different types of allosteric effectors?</p>
<p>Activators and inhibitors</p>
<p>How does the concerted model show how a small amount of substrate increases an enzymes sensitivity to a substrate?</p>
<p>Concerted model suggests that enzyme sub-units are always flipping between two conformational formations</p>
<p>Binding of S to one substrate locks the other subunits in the same conformation</p>
<p>How do allosteric inhibitors and activators function in the concerted model?</p>
<p>Activators - stabilise the the open conformation, allowing S to bind more effectively</p>
<p>Inhibitors - stabilise the ‘closed’ conformation and make it difficult for S to bind effectively</p>
<p>How does the sequential model show how a small amount of substrate increases an enzymes sensitivity to a substrate?</p>
<p>Substrate binding causes a change in<u><strong>ONE</strong></u>sub unit, this causes a change in another sub-unit allowing it to bind to S more readily</p>
<p>What enzymes are responsible for covalent modification?</p>
<p></p>
<p>Protein kinases (add phosphoryl groups to proteins)</p>
<p>Protein phosphatases (remove phosphoryl groups)</p>
<p>What do multiple phosphorylation sites allow?</p>
<p>Very fine control of enzyme funciton</p>
<p>What is an inactive precursor of an enzyme called?</p>
<p>A proprotein or a proenzyme</p>
<p>What can be produced when a proprotein is cleaved?</p>
<p>Proteases</p>
<p>Give an example of a an enzyme that is regulated by proteolytic cleavage</p>
<p>Trypsin - activated in the small intestine</p>
<p>Its precursor trypsinogen is formed in the pancreas</p>
<p></p>
<p>Describe the bonding between a protein and :</p>
<ul> <li>A prosthetic group</li> <li>A coenzyme</li></ul>
<p>Prosthetic group - Tight bonding (sometimes even covalent bonds)</p>
<p>Coenzyme - Loose bonding</p>
