Enzymes- Topic 2 Flashcards
what are enzymes?
-biological catalysts that speed up the rate of reaction without being used in the reaction itself
-globular proteins that have a specific shape (tertiary)
why are enzymes specific?
-so that they are specific in the reactions that they catalyze meaning one enzyme will only react with molecules of one substrate
where is the site of reaction in enzymes?
-the active site it has a highly specific shape and other molecules of different substrates wont fit into the active site
how do enzymes work?
-a substrate is converted into a product, the substrate first binds to the active site to form an enzyme substrate complex then the substrate is converted into a product while attached to the enzyme and finally the product is released
what is the lock and key hypothesis?
-the active site is complementary to the shape of the substrate so only one active site on each molecule and one substrate that will fit together
-the substrate fits into the enzyme like a key in a lock this specificity leads to the lock and key hypothesis
what are the forces that hold the enzyme and substrates in place?
-the forces that hold the enzyme and its substrate are weak temporary bonds e.g. usually hydrogen bonds
what is the induced fit model and how does it relate to enzyme activity?
-it has been discovered that competitors for an active site which are molecules of a similar shape to the substrate could fit, this could mean that the substrate and active site are a little flexible
-when the enzyme and substrate form a complex, structural changes occur so that the active site fits precisely around the substrate
what is the transition state in relation to the induced fit model?
-when a substrate molecule binds the active site changes shape and fits itself around the molecule which distorts it into forming the transition state
according tot he induced fit model what happens the enzyme after its finished the reaction?
-once the reaction has occurred and products are formed they move away from the active site as they can no linger fit
-the flexible enzyme returns to its original shape ready to bind to the next molecule of substrate
what is activation energy?
-the energy required to start a reaction is called the activation energy
-before a substrate can change into a product the substrate must overcome an energy barrier called the activation energy (Ea)
the larger the activation energy…
-the slower the reaction will be because only a few substrate molecules will by chance have sufficient energy to overcome the activation energy barrier
what is the equation for the transition state?
-substrate A + enzyme-> enzyme substrate complex -> product + enzyme
what do enzymes do to activation energy? how do they do this?
-lower it so that most molecules can easily get over the activation energy barrier and quickly turn it into products
-enzymes lower the activation energy by stabilizing the transition state and they do this by changing the conditions within the active site if the enzyme
what is a cofactor ?
-a non- protein chemical compound that is bound to a protein and is required for the protein’s biological activity
what are coenzymes ?
-an organic molecule that binds to the active sites of certain enzymes to assist in the catalysis of a reaction