2.4 Enzymes Flashcards
Enzymes
- Globular proteins
- Catalysts
- Specific
- active site
- pH
- Temperature
Catalysts
-Speed up the rate of reaction without being used up
Specific enzymes
-only work one molecule called a substrate
substrate
- the substance that the enzyme interacts with
- complementary shape to an enzyme’s active site
active site
the part of the enzyme that the substrate molecules bind to
how do enzyme carry out reactions?
enzymes lower activation energy
activation energy
the amount of energy needed to start a reaction
activation energy and rate of reaction
- the lower the activation energy
- the less energy needed
- so the reaction happens quicker
what happens in an enzyme reaction?
- substrate binds to active site
- Enzyme will break the bond and split it into two little products
- 2 products form joined together
- new bigger products form
Lock and Key Model
substrate has an exact right shape, it fits into active site
- like a key fits into a lock
- stays there until it is broken apart or joined together
- complementary shape
Induced Fit Model
- the shape of the enzyme is slightly different to the shape of the substrate
- the active site will be complementary to the substrate but the whole enzyme structure will be different
- substrate will push its way in and the enzyme will close around it creating more tight fit to prevent breaking away
Factors affecting enzyme activity and rate of reaction
- Temperature
- pH
Temperature and enzyme activity
-More kinetic energy
-More collisions
-Enzyme vibrates
Weak bonds broken
-Loses shape
-Denatures
what is pH
measure of H+ ions
above 7 = OH- ions
below 7 = H+ ions
pH and enzyme activity
- More H+ or OH-
- Interfere with bonds
- loses shape
- Active site loses shape
- Denatures
Enzyme Concentration and Rate of Reaction
- More enzymes
- more active sites
- More collisions
- more enzyme-substrate complex formed
- rate of reaction increases to a point
- more enzyme, no more substrates to bind with
- rate of reaction will stay the same
-substrate concentration a limiting factor
Substrate Concentration and rate of reaction
- More substrates
- faster reaction
- more collisions
- more active sites used
- rate of reaction increases to a point
-enzyme concentration a limiting factor
Inhibitors
- Reduce the rate of reaction
- Bind to enzymes
- Competitive
- Non-competitive
Competitive inhibitors
- binds to enzyme
- substrate can no longer bind with enzyme
- can’t react as it isn’t complementary but still fits into enzyme
- rate of reaction is decreased
Non-competitive inhibitors
- binding to enzyme away from active site
- changes active site shape so substrate can no longer fit in
- enzyme substrate complex cannot form
- rate of reaction decreases
Cofactors
-non-protein substances bound to enzymes
Cofactors must be present in some enzymes
Types of cofactors
- Coenzymes
- Prosthetic groups
- inorganic ion cofactor
Coenzymes
- Small, organic, non-protein molecules
- Changed and used in the reaction
- Recycled
Prosthetic groups
- permanent part of the molecule
- Usually transmission metal
- Contribute to 3D structure
inorganic ion cofactor
- increases rate of reaction
- Makes it easier for enzyme-substrate complexes to form
How a competitive inhibitor works?
- Complimentary shape
- Binds to active site
- Limited time
- Prevents enzyme substrate complex
- Less product
How an increase of substrate molecule effects rate of reaction?
- Rate increased
- Greater chance of substrate binding with active site
- More product
- Will reach maximum rate of reaction
