enzymes Flashcards
what are enzyme features?
Globular
Tertiary or quaternary structure
specificity: many enzymes have evolved to act on a single substrate or catalyse one reaction.
catalytic power: do not make reactions occur that would not occur on their own, they make them quicker.
active site?
groove in enzyme that interacts with a specific substrate to produce a reaction.
enzyme-substrate complex?
when active site binds to the substrate.
what enzyme-substrate complex’s are there?
Lock an key model
Induced fit model means the enzyme active site changes in shape (conformational change) to fit the substrate.
can reactions be reversible? are enzymes used in reactions?
Some reactions are reversible, others are not.
Substrate to substance, substance to substrate
Usually different enzymes catalyse each direction.
Enzymes are not used in reactions
what does it mean that enzymes reduce activation energy and how do they do this?
Activation energy is the energy input needed at the start of a reaction.
Catalytic power of enzymes comes from their ability to reduce activation energy so less energy is needed in the reaction.
Enzymes do this by:
Proximity and orientation: bring parts of the molecule involved in the reaction closer together and position them so that they are more likely to react.
The microenvironment: active sites are hydrophobic so the non-polar environment allows stabilising interactions such as hydrogen bonds to occur.
Ion exchange: amino acids in the active site take H+ ions from or donate them to the substrate to facilitate reactions.
how do enzymes regulate biochemical pathways?
Many reactions occur in sequences
The product of one may becomes the substrate of the next
Sequences of biochemical reactions form biochemical pathways
Some are linear, other have branches and others are cycles
what is metabolism?
collection of all biochemical (metabolic) reactions in living cells.
catabolic?
substrates are broken down and energy is released (exergonic)
anabolic
require energy to produce larger molecules from smaller substrates by making bonds (endergonic)
how may reactions be paired?
A reaction that releases energy may be coupled with one that needs it.
why do enzymes need to be regulated?
Producing too much or too little substance can be bad
Uses excess energy
Have mechanisms to protect from this
how does temperature affect enzymes?
Increases as temp increases because particles increases kinetic energy and therefore there are more collisions
Too hot, enzyme is denature, hydrogen bonds break, shape changes, binding to substrate cannot occur
At lower temps, they slow down and the bonds are less flexible so conformational changes cannot occur
reheated, they will return to normal
how does pH affect enzymes?
Enzymes function best as specific pHs
May be denatured at extremes
If pH is not ideal, active site may provide a more ideal pH
how does enzyme and substrate concentration affect enzyme activity?
High enzymes, to small substrate, fast
If substrate concentration is high, it is faster than if there was less substrate as less distance between substrate
Too much substrate, rate levels off as the active sites are taken
