FACTORS AFFECTING ENZYME ACTION Flashcards
What 2 things have to occur for an enzyme to work
1) come into physical contact with its substrate
2) have an active site that fits the substrate
What do we usually measure to see the progress of an enzyme-catalysed reaction
its time-course
What is a reactions time-course
how long it takes for a particular event to run its course
What are the 2 time-course changes are measured most frequently
1) formation of the products of the reaction
2) the disappearance of a substance
Explain the shape of the graph of enyme: substrate (as substrate decreases so does the amount of product formed, decreasing rate) using
1) at first=lots of substrate and no product
2) lots of substrate & lots of empty active sites
3) all substrates filled and substrate rapidly broken into product
4) as substrate breaks down = less substrate and more product
5) becomes more difficult for substrate to find empty active site (less substrate, more active site filled) so disappearance of substrate decreases & formation of product also decreases
6) at the end = no substrate left, so no product made
How do you find the rate of change of a graph
measuring the gradient at that point
How do you measure the gradient at that point
draw a tangent
What are the 5 factors that affect enzyme action
1) temperature
2) pH
3) enzyme concentration
4) substrate concentration
5) enzyme inhibition
In what way does temperature affect enzyme action
higher temperature = rate of reaction increases
Which 2 ways does temperature have this affect
1) Higher temperature = higher kinetic energy of molecules, meaning the molecules move around faster and are more likely to collide with each more often (enzyme & substrate).
2) Higher temperature = higher energy in collisions, so more likely to lead to a successful collision and therefore a reaction
What does temperature increase look like on a graph
rising curve up to a point
Draw a graph of the effect of a rise in temperature
rising curve (up to a point)
What happens if the temperature becomes too high
the enzyme action slows down as some hydrogen bonds are broken, far too high = denature
Why do enzymes denature
the heat breaks the hydrogen bonds in the tertiary structure of the enzyme meaning that the active site changes shape so the substrate no longer fits
Can denaturation be un-done
no
What is the optimum temperature
temperature that enzymes work best at
What is the optimum temperature for human enzymes
40 degrees C
Is the optimum temperature the same for all enzymes
no
For what 3 reasons might the human body be colder than the optimum temp for enzymes
1) more food would be required that would cancel out the benefits of higher metabolic rate
2) other proteins may be denatured at higher temperatures
3) an increased temperature during things such as illness might mean the enzymes are denatured
Why do birds have a higher body temperature than humans
they require more energy from metabolic reactions for flight
How does pH effect enzymes
at optimum pH = highest rate of enzyme-controlled reactions, extreme higher/ lower = enzymes denatured
What is the pH of a solution
a measure of its hydrogen ion content
How do you calculate pH
-log10(H+)
Which 2 ways does pH alter enzyme action
1) changes the charges on the amino acids that make up the active site, so the substrate can no longer become attached to the active site
2) the H+ and OH- ions in acid & alkalis can break the ionic and hydrogen bonds that maintains the enzymes tertiary structure
