Enzymes - Rate of Reaction Flashcards
what is the effect of increasing temperature
increases the rate of reaction due to increasing kinetic energy of the molecules. there are therefore more collisions between molecules.
explain collision theory
- substrate must collide with active site of enzyme with enough force for reaction to occur.
- if the kinetic energy of both molecules is increased by heating, there are more collisions with more force
- leading to a higher rate of reaction and more product formed.
what is the unit of rate of reaction
s^-1
what is the formula for rate of reaction
1/time taken to reach end point
what is the temperature coefficient
the increase in the rate of a process when the temperature is increased by 10 degrees
what is the formula for temperature coefficient
Q10 = rate of reaction at (T+10) degrees/ rate of reaction at T degrees
what is the optimum temperature
the temperature that gives the enzyme’s maximum rate of reaction
what happens when the bonds in the tertiary structure are broken by increased kinetic energy and vibrations
denaturation
what is denaturation
where the tertiary structure of the enzyme is changed to the point that the enzyme no longer works
is denaturation reversible
no
how can temperature cause denaturation
- increased kinetic energy makes the molecules vibrate, breaking the weaker hydrogen and ionic bonds
- these bonds are vital in maintaining the tertiary structure and hence the shape of the active site
- rate of reaction decreases, and if enough bonds are broken the whole tertiary structure will unravel
what is pH
a measure of the hydrogen ion concentration
what do hydrogen ions affect
the ionic and hydrogen bonds in the tertiary structure
how does pH affect the tertiary structure of protein
- affects the distribution of charge
- the active site relies on charged R-groups of the amino acids that make up the active site in order for enzyme to function
- H+ ions are attracted to negatively charged groups and cluster around them. Interferes with binding of substrate to active site
define optimum pH
the pH that gives the enzyme’s maximum rate of reaction
does denaturation always occur when pH changed below or above optimum
no, minor changes do not denature enzymes. The bonds that are disrupted can reform if pH returns towards optimum
how does substrate concentration affect rate of reaction
as concentration of substrate increases, collisions with enzymes become more frequent, more product is made and rate of reaction increases
eventually, rate reaches a maximum as all active sites are occupied at all times so any further increase in substrate conc. has no effect
how does enzyme concentration affect rate of reaction
increased enzyme concentration increases rate as there are more frequent collisions between enzymes and substrates, rate will reach a maximum eventually if substrate concentration remains fixed.
what does enzyme concentration or availability depend on
the rate of synthesis of the enzyme, and its rate of degradation, which are directly controlled by the cell
how is enzyme synthesis controlled in cells
depending on the cell’s needs, genes for synthesising particular enzymes can be switched on or off
how does enzyme degradation occur in cells
proteins are broken down into their amino acids and these are used to make new proteins
why is the breakdown of proteins in cells advantageous
- it removes any proteins that could accumulate and damage the cell
- it regulates metabolism by eliminating unneeded enzymes
when is the reaction rate the highest
when the enzyme and substrate are first mixed (initial reaction rate)
why does the rate of reaction decrease as the reaction progresses
the substrate is used up and thus collision are fewer. product molecules also get in the way or even inhibit enzymes
why do plateaus occur
either enzyme or substrate concentration limit any further increase in the rate of reaction
how is the initial reaction rate calculated
plotting a tangent on the steepest part of the curve and calculating the gradient
how can you measure the rate of reaction
- measure how much product appears over a period of time
- measure how much substrate disappears over a period of time
why would we use a thermometer to measure temperature of a reaction mixture, even is the experiment is being carried out in a water bath
temperature may change in the reaction mixture, especially if the reaction is exothermic
