4.1-4 Enzymes Flashcards
1
Q
What do enzymes do?
A
- increase the rate of reaction by lowering the activation energy of the reaction they catalase
2
Q
What is the active site?
A
- the area of the enzyme where the reaction with the substrate takes place
3
Q
What is enzymes relation to substrates?
A
- enzymes are specific to substrates they bind to meaning that only one type of substrate fits into the active site of the enzyme
4
Q
What happens when the enzyme and substrate form a complex?
A
- the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate
- this is called the induced fit model
5
Q
What are the four factors effecting the rate of enzyme controlled reactions?
A
- enzyme concentration
- enzyme pH
- temperature
- substrate concentration
6
Q
How does enzyme concentration effect the rate of reaction?
A
- the rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to
- increasing enzyme concentration beyond a certain point has no effect on the rate of reaction as there are more active sites than substrates so substrate becomes the limiting factor
7
Q
How does substrate concentration effect the rate of reaction?
A
- as concentration of substrate increases, the rate of reaction increases as more enzyme-substrate complexes are formed
- beyond a certain point the rate of reaction no longer increases as enzyme concentration becomes the limiting factor
8
Q
How does temperature effect the rate of reaction?
A
- rate of reaction increases up to the optimum temperature, which the temperature at which enzymes work at their maximum rate
- rate of reaction decreases above the optimum temperature as enzymes can denature
9
Q
What is an inhibitor?
A
- a substance which slows down or stops a reaction by affecting the binding of substrate to enzymes
- can be reversible or irreversible
10
Q
Examples of irreversible inhibitors are …
A
- heavy metal ions such as mercury and silver which cause disulphide bonds within the protein structure to break, as a result causing the shape of active site to change, thus affecting protein activity
- cyanide which is nerve gas that covalently binds to the active site, therefore preventing the binding of the substrate
11
Q
What in an reversible inhibitor?
A
- bind to the active site through hydrogen bonds and weak ionic interactions therefore they do not bind permanently
- can either be competitive or non-competitive
12
Q
What are competitive inhibitors?
A
- are similar in structure to the substrate molecule therefore they bind to the active site of the enzyme, decreasing its activity as they compete with substrate for the enzyme
- the amount of product formed remains the same, however the rate at which product formation occurs decreases
13
Q
What is the effects that occur in the change of concentration in the competitive inhibitors?
A
- the high the concentration of competitive inhibitor the lower the reaction rate
- increasing the substrate reverses the effect of competitive inhibitors by out-competing them
14
Q
What are non-competitive inhibitors?
A
- it binds at another site on the enzyme known as the allosteric site
- binding of the non-competitive inhibitors changes the shape of the active site therefore preventing the binding of the substrate
- increasing the concentration of substrate has no effect on non-competitive inhibition
15
Q
Examples of inhibitors …
A
- drugs
- penicillin which is used to fight bacterial infections, it is an inhibitor of enzyme transpeptidase which plays an important role in cell wall formation
- ritonavir which is an antiretroviral drug used to treat HIV which inhibits HIV protease which is responsible for assembly of new viral particles and spread of infection
16
Q
What is a cofactor?
A
- a non-protein compound required for the enzyme’s activity to occur
17
Q
What are the three types of cofactor?
A
- coenzymes
- activators
- prosthetic groups
18
Q
What are coezymes?
A
- organic cofactors which do not bind permanently
- they facilitate the binding of substrate to enzyme
19
Q
Coezymes are vitamin deprived, what are examples of this?
A
- NAD derived from niacin, which acts as a hydrogen acceptor
20
Q
What are activators?
A
- inorganic metal ions which temporarily binds to the enzyme and alters its active site, making the reaction more feasible
21
Q
Example of activators is …
A
- magnesium ions are important activator which is involved in processes such as shielding negative charge
22
Q
Where are prosthetic groups found?
A
- are permanently attached to an enzyme
23
Q
Examples of prosthetic groups are …
A
- haemoglobin contains a prosthetic haem group which contains iron, permanently bound to the molecule, which serves as a means of binding oxygen
24
Q
What is substrate concentration in the role of collisions?
A
- once all of the enzymes active sites are full, adding more substrate won’t make much of a difference
25
Why did the lock and key theory swap to the induced fit theory?
- theories are moved by the more experimental theories
26
Enzymes are proteins formed in the cell but work/ react differently. What are the two categories of this?
extracellular = work outside the cell
intracellular = work in the cell
27
Two examples of intracellular reactions are ...
lactase = breaks down lactose into glucose and galactose
catalase = breaks hydrogen peroxide down into water and oxygen
28
Two examples of extracellular reactions are ...
amylase and pepsin = work outside the cell in the human digestive system
amylase = is secreted by salivary glands, it catalyses the hydrolysis of starch into maltose
29
What is product inhibition?
- metabolic pathways are often a series of reactions
- many enzymes are inhibited by the product of their reaction
- end production inhibition is when the final product inhibits an enzyme acting earlier in the pathway
