Enzymes Flashcards
how do enzymes increase the rate of reactions
it lowers the activation energy of the reaction
describe the induced-fit model and the breakdown of substrate into product
- the substrate is similar in size to the active site of the enzyme
- it fits into the active site
- the active site changes shape to become complimentary to the substrate (induced-fit)
- this forms the enzyme-substrate complex
- the activation energy for the reaction is lowered, and the substrate bonds are put under strain
- the substrate changes into product, this is then released from the active site
- the enzyme changes back to its original shape, unused
describe a one-off reaction graph of an enzyme
- the initial rate of reaction is fastest (there is more substrate so a higher frequency of ESCs formed)
- rate of reaction slows (more substrate is converted into product, so less ESCs form)
- line plateaus (reaction stops as all substrate is converted into product)
describe an enzyme concentration graph
- increasing the enzyme concentration increases rate of reaction (they are directly proportional to each other)
- more active sites are available, more ESCs formed so product is formed at a higher frequency
describe an enzyme PH graph
- changing PH from optimum causes disruption of the tertiary structure of the enzyme
- tertiary bonds distorted, distorting shape of the active site
- fewer ESCs can form
- extreme PHs will denature enzyme completely
describe a substrate concentration graph
- at lower concentrations of substrate not all active sites are occupied
- increasing substrate concentration increases frequency of successful collisions, more ESCs are formed
- high substrate concentration all the active sites are occupied so rate is at its maximum
describe a temperature graph
- increasing temperature increases the frequency of successful collisions (more kinetic energy) increasing frequency of ESCs formed
- as the temperature increases above optimal the enzymes denature, their r-group bonds in the tertiary structure break, the active site is changed and cannot bind to the substrate - rate rapidly decreases
does increasing amount of substrate increase the initial rate of reaction
no, the number of enzyme sites are the same. the availability of the enzymes active sites become a limiting factor
name the two classes of enzyme inhibitors
competitive and non-competitive
describe how a competitive (reversible) inhibitor works
- its similar in shape to the substrate
- ‘fits into’ and blocks the active site of an enzyme
- this prevents substrate binding, and no enzyme-substrate complexes can form
how can enzymes with a competitive inhibitor reach v-max
the substrate concentration can dilute the inhibitor so v-max can be reached
describe how non-competitive (reversible) inhibitors work
- binds to an allosteric site (a site on the enzyme other than the active site)
- this changes the shape of the active site
- blocks the active site, prevents substrate binding
- no ESCs formed
why wont enzymes with the non-competitive inhibitors reach v-max
increasing the substrate won’t affect the non-competitive inhibitor, it will not be diluted as it binds to a different place than the substrate
substrate A-enzyme 1 = substrate B-enzyme 2 = substrate C-enzyme 3 = product D
using enzyme feedback inhibition describe how this is self-regulating
- Once formed, product D acts as a non-competitive inhibitor for enzyme 1
- with lots of product D produced, eventually its production will stop due to its abilities as a non-competitive inhibitor.
- when D stops being produced, so does the inhibitor meaning enzyme 1 can begin to turn substrate A into product again, continuing the cycle and producing product D
how are enzymes specific
the shape of their active site is complementary to the shape of the substrate they will turn to product
