4.2 - Factors Affecting Enzyme Activity Flashcards
How can factors affecting enzyme activity be investigated
Measuring rate of reactions they catalyse
Effect of temperature
Increasing temperature increases kinetic energy of particles.
As temp increases, particles move faster and collide more frequently
In enzyme controlled reaction, increase in temperature will result in more successful collisions = increase rate of reaction
Temperature coefficient
Q10. Measure of how much rate of reaction increases with a 10C rise in temp. Usually taken as 2 for enzymes (reaction doubles with 10C rise)
Denaturation from temperature
Enzymes are proteins.
Structure is affected by temperature.
At higher temperatures, bonds holding protein together vibrate more.
As temp increases, so do vibrations until bond strains and breaks.
Bond breakage causes tertiary structure of enzyme to change shape until it’s been denatured.
What happens when enzyme is denatured
Active site changes shape and is no longer complementary to substrate. Substrate no longer fits into active site and enzyme ceases to act as catalyst.
Optimum temperature
Temperature at which enzyme has highest rate of activity
Optimum temperature for many enzymes in human body
40*C
Optimum temperature for many thermophilic bacteria
70*C
Optimum temperature for enzymes in psychrophilic enzymes
Below 5*C
Difference between temperature being too high or too low
High - decrease is rapid denatured as active site has changed
Low - decrease less rapid as enzyme is just less active
Extremely cold environments
Deep oceans
High altitudes
Polar regions
Features if enzymes adapted to the cold
More flexible structures so are less stable than enzymes that work at higher temperatures
Smaller temperature changes denature them
What is a thermophile
Organism adapted to very hot environments
Examples of hot environments
Hot springs
Deep sea hydrothermal vents
Features of thermophilic enzymes
More stable due to increased number of bonds particularly H bonds and sulcus bridges in tertiary structures
Shape of enzymes and active sites are more resistant to temperature rises
What is a change in pH
Change in H ion concentration
Why is pH important
Active site will only be correct shape when in certain H ion concentration
How are proteins held in their precise 3D shape
H bonds & ionic binds betwieeen amino acid R groups. Bonds result from interactions between the polar and and charged R groups present on amino acids forming the primary structure
What happens when pH changes from optimum
Structure of enzyme and active site site is altered.
If pH returns then protein returns to normal shape and catalyse reaction - renaturation
How does H ion concentration affect enzymes
H ions interact with polar and charged R groups
Changing concentration changes degree of interaction
Interactions affect how R groups interact
Effect of more H ions
Less R groups can interact
Bonds break and shape of enzyme changes
Why does enzyme only function in narrow pH range
Shape of enzyme changes as pH changes
Enzyme and substrate concentration
Increased number of either increases rate of collision of active site and substrate
Increases number for enzyme substrate complex
RoR can reach Vmax
What happens at Vmax
All active sites are occupied. RoR can only be increased by increasing enzymes or temperature
