enzymes Flashcards
what is the lock and key theory
enzymes have a specific shaped active site which is complementary to the shape of the substrate
what is the product in the lock and key model
an enzyme-substrate
does the active site change shape once the product is released
no
what is the induced fit model
the substrate collides with the active site and the active site changes shape to fit the substrate
what is the product of the induced fit model
an enzyme-substrate complex
why does the induced fit model have a low activation energy
the shape change in the enzyme places a strain on the substrate lowering the activation energy
what happens once the product is released in the induced fit theory
active site returns to original shape
what is activation energy
the extra energy that is required to enable a reaction to occur
eg heat
what are enzymes
biological catalysts that are able to lower the activation energy of a reaction to allow it to proceed quicker at lower temps so that molecules can be broken down to form new ones
what does starch break down into
maltose
enzyme- amylase
what does lipids break down into
fatty acids + glycerol
enzyme- lipase
what does protein break down into
amino acids
enzyme- protease
what does lactose break down into
glucose + galactose
enzyme- lactase
why is lysozyme antibacterial
it breaks down (hydrolysis) the polysaccharide (peptidoglycan) in bacteria cell walls, it does this by catalyzing the glyosidic bonds
the chains of modified beta glucose molecules are broken
what do reactions make up
the metabolism
what are the two types of reactions
catabolic and anabolic
what is a anabolic reaction
involve larger molecules being made by the condensation of smaller molecules
what is a catabolic reaction
involve the break down of larger molecules to smaller ones
how are enzymes made
protein synthesis
what are the two types of enzymes
intracellular- remain inside the cell
extracellular- secreted from cells to function
what is the turnover number
maximum number of substrate molecules it can convert to product molecules per until time
what must be successful for enzymes reactions to happen
collisions between active site and substrate
factors that effect enzymes
temp, pH, substrate conc., enzyme conc., presence of inhibitors
ways to measure enzyme catalysis
time taken
rate of reaction
no. of conc of the product molecules formed
how does temperature effect time taken
- mean time taken is high at low temps as kinetic energy is low so not many ESC formed
2.time taken keeps decreasing as temp is increasing more ESC are formed - once its reached optimum temp, theres a max turnover number of ESC
- as temp increases above optimum, the active site is changing shape (denatured) as hydrogen bonds are being broken due to increased kinetic energy
how does temperature effect the rate of reaction
- rate is low as temp is low so theres less kinetic energy and less ESC produced
- rate is increasing exponentially because the temperature is increasing. ESC is increasing as more frequent successful collisions
- at optimal temperature so max turnover number of ESC is forming- increased kinetic energy
- denaturisation- rate is exponentially decreasing although the temp/kinetic energy are highest. active site is changing shape as site is changing shape as hydrogen bonds are breaking due to kinetic energy vibrations
how does temp effect total mass of product produced over time
40 degrees- quicker rate of reaction due to higher temperature but will level due to denaturisation or no reactants left
30 degrees- rate of reaction is slower due to less kinetic energy so takes longer
how does pH effect time taken for reaction to occur
A- at optimal pH so time taken for reaction to occur is lowest, ESC are forming at quickest
B- reaction will still be happening but not as much. small reversible changed in enzyme structure
C- highest mean time taken enzyme is not optimum as too acidic/alkaline. active site of enzyme is cahnging as ionic bonds breaking away from tertiary structure of protein. hydrogen bonds also affected
what are 4 ways enzymes can be immobilized
physical absorption
covalent binding
entrapment
Membrane confinement
what is an immobilized enzyme
an enzyme that is attached to an insoluble/inert material to prevent mixing with the product
what is physical absorption
A weak physical force attaches the enzyme molecules to the surface of support particles. This is often caused by a combination of hydrophobic effects and salt links.
what is covalent binding
The enzyme is retained on support surfaces by forming covalent bonds.
what is entrapment
The enzyme is physically enclosed in a small space, such as within cross-linked polymers.
what is membrane confinement
The enzyme molecules are confined within a semipermeable membrane
what is the advantage to using immobilised enzymes over free enzymes
Immobilisation stabilises the enzyme molecules and they have a wider range of optimum pH and temperature. It is less affected by temperature and pH changes.
why does immobilizing enzymes have this effect
By immobilising enzymes in an inert (non-reactive) substance this reduces the ability of the polypeptide chain to move and changes to temperature and pH have less of an effect on the 3D shape of the enzyme.
what are the advantage of using immobilized enzymes in industry
The enzyme can be recovered and reused:
- this reduces costs
- it also means that only small amounts of an enzyme are needed
- the product is also not contaminated by the enzyme
- several enzymes can be used at once each acting on a specific substrate.
Lower/higher temperatures can be used and still have higher yields than using the free enzyme.
example of using immobilized enzymes in industry
An industrial example is the use of immobilised lactase, which is used to produce lactose-free milk:
- the enzyme is immobilised in alginate gel beads
- milk is passed over the beads and the enzymes digest the lactose into glucose and galactose
- the milk is not contaminated by the enzyme and the beads can be used many times.
why can immobilized enzymes be used as biosensors or analytical reagents.
enzymes are specific to a particular substrate
why is the glucose oxidase electrode an example of a biosensor that is important for diabetics
it can detect glucose levels in the blood.
how does the biosensor work
- the enzyme glucose oxidase is immobilised in a gel
- a small sample of blood is passed over the enzyme
- when glucose in the blood comes into contact with the enzyme, a reaction occurs, which releases energy (chemical)
- the energy released is converted into electrical impulses
- the more energy released, the higher the concentration of glucose in the blood
- a digital display of accurate concentration is available by referring to reference data stored in the processing unit.
what is a biosensor
equipment that can detect a specific molecule
how to produce industrial enzymes
- Enzymes are produced by culturing microbes (bacteria and fungus)in fermentation vessels
- The microbes produce enzymes as part of their normal metabolic activities.
- microbes are then killed and the enzymes are extracted. And the culture is purified
- enzymes added to substrate to catalyse reactions which would be difficult to carry out otherwise.
Why enzymes are used in large scale industrial production
- they are biological catalysts and speed up rate of reaction.
- lower activation energies so reactions occur at lower temperatures saving energy and increasing efficiency.
- Enzymes are specific, so there are few side reactions and so less waste products are formed which means fewer stages in the purification process.
how do you immbolilize an enzyme
- Substrates (e.g. maltose) are trickled through the vessel from the top
- Reaction occurs as the substrate passes the immobilised enzymes
- Products (e.g. glucose) are collected from the bottom
disadvantages of immobilised enzymes
- In adsorption the enzyme may become detached.
- If enzymes are held within a substance (eg alginate bead) the substrate must diffuse into the gel which takes time.
- Free enzymes can access the substrate immediately and reaction rates are therefore faster than using immobilised enzymes.
- The presence of the alginate gel can alter the shape of the active site reducing activity compared with free enzyme.
- Chemically bonding the enzyme is a complex process and is expensive.
- Any contamination is costly because the whole system has to be shut down and the vessel re-sterilised.
what is a competitive inhibitor
when it binds to the active site so the substrate can attach and form products
is a competitive inhibitor reversible
yes, it can be removed
is the concentration of competitive inhibitor is high what happens to the rate of reaction
decreases as active sites are less avaiable for substrates
what is a non-competitive inhibitor
when it binds to the allosteric site and changes the shape of the active site/teriary structure so it cant bind to substrates
is non-competitive inhibitor reversible
no, the enzyme is no longer functional
