1A Enzymes Flashcards
What are enzymes?
PROTEINS that act as biological CATALYSTS for METABOLIC REACTIONS
How do enzymes act as catalysts?
They can LOWER the ACTIVATION ENERGY needed for reactions which INCREASES the RATE OF REACTION
How are enzymes useful in joining reactions?
By attaching to enzymes, substrates can be pulled closer together which REDUCES REPULSION so are more likely to bond
How are enzymes useful in breakdown reactions?
Fitting into an active site puts STRAIN on bonds within the substrate so it breaks up more easily
Describe the induced fit model.
> The subrstrate FITS into and BINDS to the enzyme’s active site and causes it to CHANGE SHAPE before the reaction is carried out
After the products are released, the active site returns to its ORIGINAL SHAPE
What makes enzymes so specific?
The substrate has to be able to FIT into and BIND with the active site as well as make the active site CHNAGE SHAPE meaning enzymes are only likely to bond with one particular substrate
What are the four key factors that affect enzyme activity?
Temperature, pH, enzyme concentration and substrate concentration
Explain how temperature affects enzyme action.
> INCREASED temperature leads to INCREASED ROR - molecules have more kinetic energy so collisions are more likely
However, if temperature gets too high, the reaction STOPS because VIBRATION from INCREASED KINETIC ENERGY BREAKS the bonds in the enzymes
This causes the active site to CHANGE SHAPE and the enzyme denatures
Explain how pH affects enzyme action.
> All enzymes have an OPTIMUM pH value
>/< that the optimum and H+/OH- IONS (found in ACIDS AND ALKALIS) can break HYDROGEN BONDS in an enzyme’s TERTIARY STRUCTURE
This causes a change to the SHAPE of the ACTIVE SITE and enzymes become DENATURED
Explain how enzyme concentration affects enzyme action.
> GREATER enzyme concentration means that E-S COMPLEXES are MORE LIKELY to form due to more COLLISIONS so ROR INCREASES
However, if amound of SUBSTRATE is LIMITED, ROR only increases with enzyme concentration until there is enough to deal with the substrate
Explain how substrate concentration affects enzyme action.
> INCREASED substrate concentration leads to an INCREASED ROR as collisions are more likely
However, this is only true up to a SATURATION POINT
After this, there is too much substrate for enzymes to cope with (as ALL ACTIVE SITES ARE FULL)
What are the two types of enzyme inhibition?
Competetive and non-competetive
Decsribe the process of competetive inhibition.
> Competetive inhibitors have SIMILAR SHAPES to the substrate so they can compete to bind with the ACTIVE SITE
The active site is therefore blocked meaning FEWER E-S COMPLEXES can form
Describe the process of non-competetive inhibition.
> Non-competetive inhibitors bind to the enzyme AWAY from the active site
This causes the active site to CHANGE SHAPE so substrate molecules are no longer COMPLETEMENTARY and cannot bind
