Unit 3 Chapter 3 - Enzymes Flashcards
What is metabolism?
all the biochemical reactions that occur in living cells
What are biochemical pathways?
chemical reactions in cells that occur in a seriers of controlled steps
What do reactant molecules need to product molecules?
they require ACTIVATION energy to be supplied which will strain and break their bonds
What ddoes to catalyse mean?
to speed up a reaction
What are enzymes and what do they have?
mostly proteins (tertiary or quaternary) that have been folded so they have a specific active site
How is an enzyme-substrate complex formed?
The active site of complementary in shape to a specific substrate so when the substrate binds to the active site, the enzyme-substrate complex is formed.
What happens after the enzyme-substrate complex is made?
- chemical bonds are broken in th substrate to form a new product
- the enzymes release the product
- they are not used up in the reaction so can be recycled
How do enzymes lower their activation energy?
weakening critical bonds within the substrate molecule
What is the key and lock model?
- enzyme has a complementary shaped active site to substrates shape so an exact fit is achieved
What is an induced fit model?
shape of enzymes active site changes slightly to accomodate the substrate
What are the 9 key features of enzymes?
- reusable
- specific
- reversible
- speed up, not create
- have an active site
- are proteins
- are a subset of catalysts
- act on entire biochemical pathways
- end in ‘-ase’
- above the arrow
How can temperature impact enzyme activity?
- as temp increases, there is more kinetic energy
- meaning more collisions between the enzyme and substrate
- forming more enzyme substrate complexes
- as temp increase, ROR increases
What temp do enzymes work best?
at the temp of their environment (optimal temp)
What happens if the temp is VERY high?
- enzymes protein structure is permanently changed
- substrate cannot bind to active site as enzyme is denatured
- remains inactive even when temp is returned to normal
What happens if the temp is VERY low?
- not denatured
- reduced activity resulting in less collisions between enzyme and substrate
- active site shape is not changed
- becomes active again with temp returns to normal
What level of pH does an enzyme work best?
optimal pH
What does a change in pH result in?
- change in the shape of an enzyme
- affect ability to combine with substrate
- reduction of enzyme activity
Can enzymes be denatured by pH?
- both extremes of the optimal (optimal is pH 7)
eg, 1 and 13 would denature
Why does enzyme activity plateau?
due to running out of substrate
How can the effect of enzyme concentration impact enzyme activity?
- increasing concentration of enzume means there are more avaliable active sites for the substrate to bind to
- ROR increases as long as there is avaliable substrate
- at the point where enzymes are in excess, the reaction rate with plateau
How can the effect of substrate concentration impact enzyme activity?
- adding more substrate will increase the ROR until all the active sites are occupied
- at the saturation point, the ROR will stop increasing
What does the saturation point mean?
- all the avaliable active sites are occupied with substrate
What are the 2 types of enzyme inhibitors?
- competitive inhibitors
- non-competitive inhibitors
What are competitive inhibitors?
- molecule that competes with a substrate for the active site
- shape is complementary to the active site
- if bonding is permanent, reduces the ROR by inactivating the enzyme
- is fatal
What are non-competitive inhibitors?
- molecule which binds to enzyme at the allosteric site
- changes shape of the enzymes active site so substrate can no longer bind
What are the competitive inhibitors impact on the ROR?
- if concentration of subtrate is increased, maximum ROR can still be reached (out compete inhibitor molecules)
- extra substrate makes the substrate molecules abundant enough to consistently out compete the inhibitor molecules to the active site
What are the non-competitive inhibitors impact on the ROR?
- maximum ROR will never be reached even with lots of substrate
- because the active site has either had a conformational change, so substrate can’t bind
- no matter how much or little substrate, maximum not reached
When does feedback inhibition occur?
- when a product produced acts as an inhibitor of an enzyme at the start of a pathway
What happens when too much product is being produced?
- it can bind to the enzyme and slow or stop its activity
What happens when there is less product?
- the product molecule detaches and the enzyme can make more product
