Enzymes Flashcards
What are enzymes?
biological catalysts- speed up the rate of metabolic reactions but are unaltered by those reactions so reusable
What type of proteins are enzymes?
globular
How do enzymes act as catalysts?
enzyme combines with substrate to form enzyme-substrate complex
thereby lowering the activation energy
What is activation energy?
the energy required for a reaction to proceed
Why is lowering the activation energy useful?
it allows chemical reactions to proceed at body temperature
What is the part of an enzyme that the substrate combines with?
the active site
How many active sites could each enzyme have up to?
30
Typically how many amino acids residues does the active site consist of?
3 to 12
What is enzyme specificity?
the shape of the active site is complementary to the shape of the substrate (exact fit), thus the substrate fits into the active site to form an enzyme substrate complex
What us the lock and key mechanism?
substrate fits exactly into the active site of the enzyme, no other types of substrate will fit it
What is the induced fit mechanism?
When the substrate binds to the active site, it induces a conformational change in the enzyme (enzyme changes to fit with substrate better)
What do oxidoreductases do?
catalyse oxidation and reduction reactions
What do hydrolases do?
catalyse hydrolysis reactions
How does temperature affect the rate of an enzyme controlled reaction?
an enzyme works best at a certain temperature this is the optimum temperature
before this temperature a enzyme works at a lesser rate
after this temperature the enzyme begins to denature and so will work at a lesser rate and steeply fall off to not at all
How does pH affect the rate of an enzyme controlled reaction?
enzyme works best at a certain pH, optimum pH
slight variations from this pH the enzyme will work at a slightly lesser rate, the further alkaline/acidic the pH goes the enzyme will denature until it does not catalyse the reaction at all
What happens as substrate concentration increases?
there are more successful random collisions between the enzyme and the substrate and the rate of reaction increases
What is a limiting factor as substrate concentration increases?
enzyme concentration
What happens as enzyme concentration increases?
there are more active sites to enable more enzyme-substrate complexes to be formed and the rate of reaction increases
What is a limiting factor as enzyme concentration increases?
substrate concentration
What is competitive inhibition?
when an inhibitor interferes with active site of enzyme by binding to it, so the substrate cannot bind
What is non-competitive inhibition?
when an inhibitor binds to an allosteric site of an enzyme, and this changes the shape of the enzyme so the substrate cannot bind to it
What is enzyme technology
enzymes extracted and purified from microorganisms
such enzymes are used in extensively in industry, medicine and food technology
over 2000 enzymes have been identified: of these over 150 are used in industrial processes
Why are enzymes useful in technology?
they are catalysts (speed up reactions)
can be re-used
they are specific, therefore act on specific substrates and produce specific products
factors which affect their activity can be easily controlled
they are biodegradable, environmentally friendly
they can be immobilised (adherence onto the surface of inert material by adsorption)
How can enzymes be immobilised?
by absorbing them to. or ‘trapping’ them in an inert, insoluble material (e.g. cellulose fibres, semi-permeable membranes, agar gels, polyacrylamide)
What are some advantages of immobilised enzymes?
they can be re-used without the need to seperate them from the products
they can be used in continuous processes
some enzymes are more stable when immobilised
several enzymes (with different temperature and pH optimums) can be used together
Can be easily added or removed giving greater control over the reaction
If an enzyme is more stable when immobilised what does this have an effect on?
they are less likely to be denatured by high temperatures and pH extremes.
What are some disadvantages of immobilised enzymes?
not all of the active sites can be accessed when adhered to a bead
need to increase enzyme concentration to compensate for this
What is the source, optimum temp and pH of enzyme cellulase?
fungus
65 degC
pH 5.0
What is the source, optimum temp and pH of enzyme pectinases?
fungus
35 degC
pH 5.5
What is the source, optimum temp and pH of enzyme a-amylase?
bacterium
95 degC
pH 7.0
What is the source, optimum temp and pH of enzyme proteases?
bacterium
45 degC
pH 6.0
What is the source, optimum temp and pH of enzyme lactase?
yeast fungus
48 degC
pH 6.5
What is the source, optimum temp and pH of enzyme lipase?
fungus
35 degC
pH 7-11
What is an application of cellulase enzyme?
breakdown of cellulose sugar to make fermentable sugar
What is an application of pectinase enzymes
increase juice yield from fruit
What is an application of a-amylase enzyme?
breakdown of corn starch in sugar industry
What is an application of protease enzymes?
biological detergents
What is an application of lactase enzymes?
production of ‘lactose free’ milk
What is an application of lipase enzymes?
biological detergents
What are Pectinases S & C used in?
extraction and clarification of fruit juices
What are pectins and where are they found?
polysaccharides found in plant cell walls
What do pectinases do?
group of enzymes which catalyse the hydrolysis of pectins
What are pectins broken down into by pectinases?
smaller soluble molecules, cells separate from each other & juice is easier to extract
What do proteases do?
catalyse the hydrolysis of proteins and thus contribute to the breakdown of protein stains (e.g blood) (washing clothing)
what happens to proteases after extraction?
they are incorporated into granules (immobilisation)
What 3 types of enzymes are incorporated into biological powders?
proteases, amylases and lipases
What does the enzyme lactase do?
catalyses the hydrolysis of lactose into simple sugars (glucose and galactose)
If a person is lactose intolerant what does this mean and result in?
they are unable to digest lactose
undigested lactose passes into the colon and bacteria ferment it - resulting in abdominal pain & diarrhoea
How does the production of lactose-free milk work?
lactase is immobilised in a column, milk is poured in at the top of the column and lactose-free milk collected at the bottom
Where are immobilised enzymes trapped?
an inert polymer matrix (e.g alginate beads)
How can immobilised enzymes be sorted?
packed into a column
Biosensors - what can enzymes be used to detect?
one specific type of molecule in a mixture of molecules
What is an example of a biosensor?
enzyme electrodes
What do biosensors use and be used for?
use immobilised enzymes
for accurate, raoid detection of minute traces of biologically important molecules (e.g blood glucose level in diabetics
How does a biosensor work?
Receptors take reading of change from mixture, transducer converts change into electrical signal, sent to computer or amplifier, strength of signal proportional to substrate concentration
In a blood glucose biosensor what enzyme is used?
glucose oxidase
What does glucose oxidase catalyse?
Glucose + oxygen = gluconic acid + hydrogen peroxide
What are the 4 stages in a blood glucose biosensor?
enzyme electrode placed in blood sample
glucose diffuses into immobilised enzyme layer
oxygen is taken up
rate of oxygen uptake is proportional to glucose concentration
