3.1.4.2 Enzymes Flashcards
What is an enzyme?
A globular protein that acts as a catalyst
What is the structure of enzymes?
The structure is a result of the sequence of amino acids
The active site is the functional area of the enzyme that the substrate fits into
The substrate is specific to the enzyme because of the specific shape of the active site
What are the two ways of enzymes working?
Induced fit: proximity of the substrate leads to a change in the enzyme which forms the functional active site, enzyme is malleable
Lock and key: each enzyme has a specific active site that can only be activated by one substrate, enzyme is rigid
Scientists observed that other molecules would bind to enzymes at sites other than the active site which suggests that ‘induced fit’ is correct
What are the stages of an enzyme reaction?
Start: lots of substrate, easy for substrate to find empty active sites, all active sites are filled, substrate is rapidly broken up
Middle: amount of substrate decreases, product increases, more difficult for substrate molecules to find an active site, product molecules gets in the way
End: rate of reaction slows until change in rate can’t be measured, all substrate hasn’t been used up
How do you measure the rate of enzyme reaction?
Pick a point on the line, draw a tangent of it, work out the gradient of the line
What affects enzyme activity?
Temperature, pH, enzyme/substrate concentration
What do enzymes do?
Speeds up the rate of a chemical reaction without undergoing permanent changes themselves
They do this by lowering the activation energy
How does enzyme/substrate concentration change the rate of an enzyme reaction?
Concentration increases as rate increases
Once the number of active sites equals the number of substrate molecules, the rate of reaction doesn’t increase
How do you measure the rate of enzyme reaction?
For a graph with rate on the axis: plot the point and read off the graph
For a graph with something else on the axis: draw a tangent and measure the gradient of the line
What are the two parts of an enzyme concentration and rate reaction?
- Enzyme is the limiting factor
- Substrate is the limiting factor
What are the two parts of a substrate concentration and rate reaction?
- Substrate is the limiting factor
- Enzyme is the limiting factor
What is a competitive inhibitor?
A competitive inhibitor has a complimentary shape to the enzyme
Increasing the amount of competitive inhibitor competes against the substrate to find an active site
What is a non competitive inhibitor?
It attaches themselves to a binding site and alters the shape of the active site so that the substrate and active site are non-complimentary
Increasing the amount of substrate doesn’t affect rate
Increasing the amount of inhibitor decreases the rate of reaction
How does a disaccharide react with an enzyme?
Substrate is a complementary shape to the active site of the enzyme
An enzyme-substrate complex is formed
Reaction occurs, breaking the glycosidic bond between the disaccharide
Two glucose monosaccharides are
released
What happens when a catalyst is poisoned?
When the surface is blocked by a substance that is adsorbed permanently to the surface
This stops access to the reactants
Only happens with solid catalysts
