role of enzymes
-speed up chemical reactions
-catalyse metabolic reactions both at cellular levels (respiration) and as a whole organism level (digestion)
-can affect structure (production of collagen) as well as functions (respiration)
intercellular reactions
-within cells
-hydrogen peroxide is a toxic by product that kills cells-catalase breaks down the hydrogen peroxide to oxygen and water
extra cellular reactions
-outside cells
-amylase is found in the saliva and secretes by the mouth by cells in the salivary glands
-catalyses the hydrolysis of starch into maltose
mechanism of enzyme action
-globular protein
-active site with a specific shape that substrates bind to
-enzymes reduce the amount of activation energy (heat) needed for a reaction - speeds up the rate of reaction
lock and key model
this is where the substrate fits into the enzyme in the same way a key fits into a lock
induced fit model
the active sit changes shape slightly to fit the substrate more closely
temperature effect in enzyme activity
-temp increases, more kinetic energy so enzyme molecules move faster and vibrate more
-enzymes are more likely to collide with substrate
-energy of collision increases which means collision is more likely to result in a reaction
pH affect on enzyme activity
-above /below optimum pH, ions (H and OH) in acids and alkalis can mess up ionic bonds and ionic bonds that hold enzymes tertiary structure in place
- makes the active site change shape and denature
enzyme conc affect rate or reaction
-more enzyme molecules
-substrates can collide to form enzyme-substrate complex
-increases the rate of reaction
-substrate is limited , not enough substrate to bind with enzyme so there’s no further effect
substrate conc affect rate of reaction
-high conc, the higher rate of reaction
-more enzyme-substrate complex formed
-not enough enzyme molecules to bind with substrate molecules, no difference in rate of reaction
-substrate conc decreases over time, rate of reaction will decrease
how to calculate temperature coefficient
-shows how much the rate of reaction changes when the temperature is raised by 10C
-R2/R1
rate at higher temperature/rate at lower temperature
what are co factors
-inorganic molecules
-help the substrate and enzyme bind together
-don’t participate in reaction, aren’t used or changes
e.g chloride ions are co factors for amylase
what are co enzymes
-organic molecules
-participate in the reaction and are changed by it
-act as carriers that move chemical groups between different enzymes
-they’re continually recycled during this process
e.g vitamins are sources of co enzymes
what are competitive inhibitors
-similar shape to that of the substrate molecule
-compete with substrate molecule to bind to the active site but without any reaction
-blocks the active site for substrate
-at high conc of inhibitor, nearly all active sites are taken. decrease rate of reaction drastically
-at high conc of substrate
-substrates chances of binding increases
-increases the rate of reaction
what are non competitive inhibitors
-bind away from the active site
-bind at the **allosteric site **
-causes the active site to change shape so substrates can’t bind to it
-don’t compete because they’re a different shape
-increasing the conc of substrate doesn’t change the rate of reaction
reversible and non reversible inhibitors
- strong, covalent bonds the inhibitor can’t be removed easily and its irreversible
-weaker hydrogen bonds or weak ionic bonds , they inhibitor can be removed and its reversible
role of end product inhibition
-final product in a metabolic pathway that inhibits an enzyme that acts earlier in the pathway
Identify a change the student could make to his procedure that would increase the validity of the investigation.
equal volume in each tube
add buffer
Another student suggested that he should repeat the investigation at least twice.
How would this have improved the investigation?
- improve reliability
- calculate the mean
Pepstatin acts as a competitive inhibitor of pepsin.
What can you conclude about the structure of pepstatin?
similar shape to , substrate
complementary shape to active site
