4.2 Factors Affecting Enzyme Activity Flashcards
How does temperature affect the rate of reaction?
Higher temperature - higher KE of particles
Particles move faster and collide more often
Greater frequency of successful collisions between substrate and enzyme
Increased rate of reaction
What is the temperature coefficient, Q10?
Measure of how much rate of reaction increases with a 10oC rise in temperature
Q10 for enzyme controlled reaction
Usually taken as 2 - rate of reaction doubles with a 10oC temperature increase
Denaturing from temperature
Enzymes are proteins, so structure is affected by temperature
At higher temperatures, bonds vibrate more
As temperature increases, vibrations increase until bonds strain and break
Breaking of bonds cause the precise tertiary structure of the protein to change
Optimum temperature
Temperature at which enzyme has highest rate of activity
In humans - around 40
Thermophilic bacteria (found in hot springs) - 70
Psychrophilic organisms (in cold regions) - below 5
How are enzymes adapted to cold conditions?
They have more flexible structures
Less stable than enzymes that work at higher temperatures
Small temperature changes will denature them
How are enzymes adapted to high temperatures?
More stable than other enzymes
Increased number of bonds, hydrogen bonds and sulfur bridges
Shape of active site is more resistant to change as temperature rises
Why does pH affect enzyme activity?
Hydrogen and ionic bonds between R groups hold proteins together
Bonds are a result of interactions between polar and charged R groups present in the amino acids forming the primary structure
A change in pH changes H+ ion concentrations
Hydrogen ions interact with polar and charged R groups and this affects interaction of R groups with each other
How does pH affect enzyme activity?
Active shape will only be the correct shape at a certain H+ ion concentration (optimum pH)
When the pH changes from the optimum, the structure of the enzyme and therefore the active site, is changed
What happens in low and high pH?
Low pH, higher H+ ion concentration, fewer R group interactions
Causes bond breaking and shape of enzyme changing
High pH, lower H+ ion concentration, more R group interactions
Substrate and enzyme concentration
Increased substrate molecules - higher collision rate with active sites of enzymes, more enzyme-substrate complexes formed
Rate of reaction increases to maximum - V max
At this point, all active sites are occupied by substrate particles, no more products released
What is serial dilution?
Repeated stepwise dilution of a solution, usually done in factors of 10, to produce solutions of various concentrations
