Enzymes Flashcards
Characteristics of enzymes
- alter rate of reaction without permanent change to themselves
- reused repeatedly
- alter speed of reactions that are already occurring
- effective on small amounts
What is an enzyme
A protein that acts as a biological catalyst by lowering the activation energy of a reaction
What is an anabolic and a catabolic reaction
Anabolic = condensation
Catabolic = hydrolysis
What is the structure of enzymes
Globular proteins that have a specific 3d shape which is specified by their sequence of amino acids
Has a functional part called the active site
How does the shape of an enzyme molecule relate to its function
Has a specific 3d shape that has a complementary shaped substrate which can bind to the active site
Lock and key hypothesis
Each substrate has a complementary active site that they bind to
Support and limitations of lock and key hypothesis
Support: enzymes are specific in the reactions they catalyse so assume they fit together perfectly
Limitations: assume enzymes have a rigid structure but structure is actually flexible
Induced fit hypothesis
Before the reaction the active site isn’t complementary to the substrate but shape of active site changes as substrate binds, stressing the bonds. Only proper substrate is capable of inducing the proper alignment of the active site
How do formation of an esc increase rate of reaction
It reduces the activation energy due to bending bonds
Why would changing one amino acid prevent enzyme from functioning
Change shape of active site so no esc formed as complementary substrate wouldn’t fit
Factors affecting enzymes
- temp
- ph
- enzyme conc
- substrate conc
How does temp affect enzyme activity
Inc temp to optimum temp Inc enzyme activity due to inc in kinetic energy of molecules causing molecules to move more rapidly and collide more freq (collide with more energy for more successful collisions— more esc made
Inc temp past optimum = H bonds in enzymes break, enzyme changes shape, substrate fits less easily, tertiary structure is disrupted + enzyme denatured (permanent)
How does ph affect enzyme activity
- changes to the h bonds between r groups + ionic bonds in tertiary structure of enzyme so they break - so active site changes shape + substrate no longer fits so ESC no longer formed (denatured)
How does enzyme conc affect enzyme activity
As enzyme conc Inc so does enzyme activity as more esc can be formed as more enzymes available for substrates until point where there are enough active sites to accommodate the substrate molecules
How does substrate conc affect enzyme activity
As substrate conc Inc so does enzyme activity as enough substrate molecules to fill the active sites so more esc can be formed until point where there is enough substrate to fill all active sites and so no more esc can be formed
What is enzyme inhibition
Substances that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity
2 types of enzyme inhibitors
Competitive - diff chemical with similar shape to substrate that bind to the active site of the enzyme decreasing no of esc formed and rate
Non competitive- bind to enzyme at position other than the active site (allosteric site) which changes shape of active site so substrate can’t fit and less esc formed (permanently)
