Enzymes Flashcards
What do anabolic reactions do
build up molecules e.g protein synthesis
What do catabolic reactions do
break down molecules e.g digestion
What are enzymes
globular proteins that act as catalysts
Why are enzymes called biological catalysts
Because they are made of living cells
What is the structure of an enzyme
Protein with tertiary structure
Hydrophillic R groups on the surface making it soluble
Particular sequence of amino acids
R groups determine shape and bonds that form
What is the active site
specific 3D site which substrate binds to by weak chemical bonds
what are the general characteristics of enzymes
speed up reactions
not used up
have a high turn over rate
only catalyse reactions that are energetically favourable
what are the 3 sites of enzyme action
extracellular
intracellular in solution
intracellular membrane bound
what is an example of an enzyme acting extracellular
enzymes secreted from cells in exocytosis
what is an example of an enzyme acting intracellular in a solution
in solution inside cells e.g glucose breakdown in glycolysis
what is an example of an enzyme acting intracellular membrane bound
attached to membranes e.g mitochondria in ATP formation
what is the lock and key model
the active site and substrate are complementary to each other and it is a specific fit
what is the lock and key model
the active site shape changes slightly to acomodate the substrate
how do enzymes speed up the rate of reaction
they modify the substrate so that the reaction requires a lower activation energy
when substrate enters active site the molecules alters the shape so reactions can occur at lower temp
what is activation energy
minimum energy required in a chemical system for a reaction to occur
what is the first limiting factor in a reaction
the enzyme conc
what is the limiting factor as the reaction carries on
the substrate conc
how do you calculate rate of production
increase in mass divided by time
how do you calculate % increase in mass
actual increase in mass divided by initial mass X100
what is inactivation
reversible reduction of enzyme activity at low temp
insufficient energy to form E+S complexes
what happens to enzymes over 40 degrees
denature due to increasing breaking hydrogen bonds and altering the enzymes tertiary structure
what happens to enzymes at low temps
they become inactivated
what happens to enzymes if PH is too high
it becomes neutralised by positive OH- charges
what happens to enzymes if the PH is too low
the H+ ion attracts negative charges and neutralises them
What is enzyme inhibition
the decrease in the rate of an enzyme controlled reaction by an inhibitor
What does an inhibitor do
binds with the enzyme and stops it from forming an enzyme substrate complex
What is the effect of substrate concentration on enzyme activities
the more substrate the more successful collisions and complexes formed
What is the effect of enzyme concentration on activity
as enzyme concentration increases there are more active sites available so more complexes can form
What is the effect of pH on enzyme activities
too High
Neutralised by excess OH-ions
Too low
The H+ions neutralise negative charges
Both of these disrupt ionic and hydrogen bonds which changes the shape of the active site
How are enzymes immobilised
fixed trapped or bound on an inert matrix
What materials can be used to immobilise an enzyme
sodium alginate beads or cellulose microfibrils
How do immobilised enzymes work at higher temperatures and pH
It creates a microenvironment because trapping the molecule prevents the shape change that would denature the active site
what is an example of an inhibitor being used and how does it work
lactose free milk
milk passed through a column with immobilised lactase
lactose binds to active site and is broken Down
what are the advantages of immobilised enzymes
increased stability and function over a wide range of temperatures and pH
products not contaminated
enzymes easily recovered for reuse
why do enzymes trapped in beads have lower rate of reactions
because as is inside bead so substrate has to diffuse
readily available to bind on a matrix
