enzymes Flashcards
1
Q
what must happen for an enzyme reaction to occur
A
- there must be successful collisions to form enzyme substrate complexes
2
Q
what factors effect enzyme activity
A
- temperature
- pH
- substrate concentration
- enzyme concentration
- presence of inhibitors
3
Q
what three ways can an enzyme catalysed reaction be measured
A
- time taken for the reaction to take place
- rate of reaction
- concentration of the molecules produced
4
Q
describe the graph for the effect of temperature on enzyme activity
A
- at low temperatures there’s less kinetic energy so less successful collisions, this leads to fewer enzyme substrate complexes forming
- as temperatures increase, the kinetic energy increases leading to more successful collisions which leads to more enzyme substrate complexes
- as the temperature gets too high, the molecules will vibrate more which will weaken the hydrogen bonds which alters the shape of the enzyme causing it to denature
5
Q
describe the effect of pH on enzyme reactions
A
- at the optimum pH, the charges of the r groups are complimentary to the charges on the substrate, this will lead to more es complexes forming
6
Q
what are enzymes
A
- biological catalysts
- they speed up chemical reactions without being used up during the reaction
- globular proteins
- they are specific and only catalyse one reaction
- the active site is complimentary to the substrate and it lowers the activation energy
7
Q
what is activation energy
A
- the extra energy required to enable the reaction to occur
- often supplied as heat in laboratory reactions
- enzymes are able to lower it so reactions can take place quickly at lower temperatures
8
Q
what is the lock and key theory
A
- the active site is a specific shape that is complimentary to the substrate
- ## the binding of the substrate to the active site allows bonds to break or form more easily
9
Q
what is the induced fit hypothesis
A
- the substrate collides with the active site
- the active site molds around the substrate and kits held in position by oppositely charged groups on the amino acids in the active site
- an enzyme substrate complex is formed
- the change of shape places strain on the substrate which allows the molecules to be held closer and the reaction to take place quicker
- this lowers the activation energy
10
Q
what is a catabolic reaction
A
- involves the break down or hydrolysis of larger molecules to smaller ones
11
Q
what is an anabolic reaction
A
- involves larger molecules being made by the condensation of smaller molecules
12
Q
what are intracellular enzymes
A
- enzymes which remain inside the cell
eg - respiratory enzymes
13
Q
what are extracellular enzymes
A
- enzymes which are secreted from cells to function
eg - digestive enzymes
14
Q
what is the turnover number
A
- maximum number of substrate molecules the enzyme can convert to product molecules per unit time
15
Q
explain the effects of changing substrate concentration on enzyme reactions
A
- at low substrate concentrations, there are fewer es complexes
- at higher substrate concentrations there are more es complexes
16
Q
what is a competitive inhibitor
A
- the structure is similar to the substrate
- it competes with the substrate for the active site of the enzyme
- prevents the formation of es complexes
- reduces the rate of reaction
- adding more substrate can reduce the effect of these inhibitors
17
Q
where does a non competitive inhibitor bind
A
- the allosteric site
- this inhibitor can be irreversible
18
Q
explain industrial enzymes
A
- culturing microbes in a fermentation vessel, microbes produce enzymes as part of their metabolic activity
- microbes are then killed and the enzymes are extracted and purified
- enzymes are then added to substrate molecules to catalyse reactions
19
Q
why are enzymes used in large scale industrial production
A
- they are biological catalysts and speed up reactions
- they lower activation energy so the reactions can occur at lower temperatures which saves energy and increases efficiency
- there are few side reactions so less waste products are formed which means less stages in the purification process
20
Q
what are immobilised enzymes
A
- enzymes which are held or stabilised in an inert support or matrix
21
Q
what are the advantages of immobilised enzymes
A
- the enzymes are easily recovered and can be used over and over again
- the product is not contaminated by the enzyme
- the matrix creates a microenvironment for the enzyme so it makes it more stable at extreme temperatures
- several enzymes with different optima can all be used at the same time
22
Q
what are the methods of immobilising an enzyme
A
- adsorption = attached to glass beads, clay particles or collagen
- entrapment
- chemically bond
23
Q
what are the disadvantages of immobilised enzymes
A
- in adsorption the enzymes may become detached
- if the enzyme is held within a substance it must diffuse into the gel which may take time, free enzymes can access the substrate immediately
- the presence of alginate gel alters the shape of the active site which reduces enzyme activity
- chemically bonding is an expensive and complex process
- any contamination is costly as the whole system has to be shut down and re -sterilised
24
Q
what is a biosensor and how does it work
A
- an instrument that can detect a specific molecule in a mixture of molecules
- enzymes are specific
- an electric probe with the specific immobilised enzyme on a membrane attached is added to the blood
- if glucose is present, it diffuses through the membrane and forms an es complex
- the reaction produces a small electrical current which is picked up by the electrode
- this is then read by the monitor
25
what are the advantages of biosensors
- ability to detect very small concentrations of the target substance
- they are very accurate and easy to use
- quick to respond
- cost effective
- can be used for continuous monitoring
- the biological element can be regenerated and reused
26
what are some disadvantages of biosensors
- require extensive research and development from a skilled workforce
- require accurate calibration
