Enzymes Flashcards
1
Q
Enzymes are globular proteins that act as what?
A
Enzymes are globular proteins that act as catalysts
2
Q
Catalysts do what without doing what themselves?
A
Catalysts alter the rate of a chemical reaction without undergoing permanent changes themselves
3
Q
Catalysts can be reused how many times?
A
Catalysts can be reused repeatedly
Are therefore effective in small amounts
4
Q
Enzymes do not make reactions happen - they do what?
A
Enzymes do not make reactions happen - they speed up reactions that already occur
5
Q
Enzymes do not make reactions happen - they speed up reactions that already occur, sometimes by a factor of what?
A
Enzymes do not make reactions happen - they speed up reactions that already occur, sometimes by a factor of many millions
6
Q
Sucrose + what —> what + what? (substrates) —> (products)
A
Sucrose + Water —> Glucose + Fructose (substrates) —> (products)
7
Q
Sucrose + Water —> Glucose + Fructose (substrates) —> (products)
For reactions like this to take place naturally, a number of conditions must be satisfied:
The sucrose and water molecules must collide with what?
A
The sucrose and water molecules must collide with sufficient energy to alter the arrangement of their atoms to form:
Glucose
Fructose
8
Q
The free energy of the products of a reaction (eg. glucose and fructose from sucrose) must be what?
A
The free energy of the products (glucose and fructose) must be less than that of the substrates (sucrose and water)
9
Q
Many reactions require an initial what to start?
A
Many reactions require an initial amount of energy to start
10
Q
What is activation energy?
A
Activation energy is the minimum amount of energy needed to activate the reaction in this way
11
Q
There is an activation energy level, which must initially be overcome before what?
A
There is an activation energy level, which must initially be overcome before the reaction can proceed
12
Q
Enzymes work by doing what?
A
Enzymes work by lowering this activation energy level
13
Q
Enzymes allow reactions to take place at…. what ….than normal?
A
In this way, enzymes allow reactions to take place at a ….lower temperatures…. than normal
14
Q
What is the human body temperature
A
37 C
15
Q
Is the human body temperature relatively low in terms of activation energy?
A
Yes, this is why enzymes are important.
16
Q
Without enzymes what would happen
A
the reactions required to sustain life wouldn’t happen.
17
Q
Enzymes, being globular proteins, have a specific what?
A
Enzymes, being globular proteins, have a specific 3-D shape
18
Q
Enzymes, being globular proteins, have a specific 3-D shape that is the result of their what?
A
Enzymes, being globular proteins, have a specific 3-D shape that is the result of their sequence of amino acids (primary protein structure)
19
Q
A specific region of the enzyme is what?
A
The Active Site
20
Q
The active site is made up of a relatively small number of what?
A
The active site is made up of a relatively small number of amino acids
21
Q
The active site forms a small what within the much larger enzyme molecule?
A
The active site forms a small depression within the much larger enzyme molecule
22
Q
The molecule on which the enzymes does what is called the substrate?
A
The molecule on which the enzymes acts is called the substrate
23
Q
This substrate fits nearly into this depression and forms what?
A
Forms an enzyme-substrate complex
24
Q
The substrate molecule is held within the active site by what?
A
The substrate molecule is held within the active site by bonds
25
The substrate molecule is held within the active site by bonds that do what?
The substrate molecule is held within the active site by bonds that temporarily form between:
1. Certain amino acids of the active site
2. Groups on the substrate molecule
26
What does the induced fit model of enzyme action propose?
The induced fit model of enzyme action proposes that the active site forms as the:
Enzyme +
Substrate
Interact
27
The proximity of the substrate (a change in what) leads to what?
The proximity of the substrate (a change in the environment of the enzyme) leads to a change in the enzyme
28
The proximity of the substrate (a change in the environment of the enzyme) leads to a change in the enzyme that forms what?
The proximity of the substrate (a change in the environment of the enzyme) leads to a change in the enzyme that forms the functional active site
29
The proximity of the substrate (a change in the environment of the enzyme) leads to a change in the enzyme that forms the functional active site.
In other words, the enzyme is what?
The enzyme is flexible
30
The enzyme is flexible and can mould itself around what in the way that a glove moulds itself to the shape of the hand?
In other words, the enzyme is flexible and can mould itself around the substrate in the way that a glove moulds itself to the shape of the hand
31
As it changes its shape, the enzyme does what to the substrate molecule?
As it changes its shape, the enzyme puts a strain on the substrate molecule
32
This strain does what?
This strain distorts:
1. A particular bond
OR
2. Bonds
In teh substrate
33
This strain distorts a particular bond or bonds in the substrate and consequently does what?
This strain:
1. Distorts a particular bond or bonds in the substrate
2. Consequently lowers the activation energy needed to break the bond
34
Any change in an enzyme's environment is likely to do what?
Any change in an enzyme's environment is likely to change its shape
35
The very act of doing what is a change in its environment?
The very act of colliding with its substrate is a change in its environment
36
The very act of colliding with its substrate is a change in its environment and so what?
The very act of colliding with its substrate is a change in its environment and so its shape changes - induced fit
37
One earlier model of enzyme action proposed that enzymes work in the same as what?
One earlier model of enzyme action proposed that enzymes work in the same as a key operates a lock
Each key has a partiuclar shape and fits a particular lock.
38
One limitation of the Lock and Key model is that the enzyme, like a lock, is considered to be what?
One limitation of this model is that the enzyme, like a lock, is considered to be a rigid structure
39
One limitation of this model is that the enzyme, like a lock, is considered to be a rigid structure.
However, scientists had observed that other molecules could do what?
Scientists had observed that other molecules could bind to enzymes at sites other than the active site
40
Scientists had observed that other molecules could bind to enzymes at sites other than the active site.
In doing so, they altered what?
In doing so, they altered the activity of the enzyme
41
The induced fit model is therefore a what version of the lock and key model?
The induced fit model is therefore a modified version of the lock and key model
which better reflects the observations of scientists regarding the flexibility of the enzyme structure.
42
What is Free energy
Free energy is the energy of a system that is available to perform work
43
Inside the cell is what?
Intracellular
44
Outside the cell is what?
Outside the cell is extracellular
45
An initial input of energy (activation energy) starts a reaction that then does what?
An initial input of energy (activation energy) starts a reaction that then continues of its own accord
46
The substrate does not have the 'same shape' as the active site.
The substrate has a complementary shape to the active site
47
Enzymes have an active site, but not all proteins are enzymes.
Proteins, that are not enzymes, have actiev sites and these are called?
Many proteins have:
1. Binding sites
Or,
2. Receptor sites
that are not active sites
48
Some hormones are proteins and these have receptor sites, but they are not what?
Some hormones are proteins and these have receptor sites, but they are not active sites
49
Enzymes catalyse what reactions?
Enzymes catalyse both:
1. Anabolic
2. Catabolic
reactions
50
Anabolic reactions
are?
Anabolic reactions are reactions that build up molecules
51
Catabolic reactions are
Catabolic reactions are reactions that break down molecules
52
Metabolism is
Metabolism is all the chemical processes that take place in living organisms
53
A Catalyst is?
A catalyst is a substance that speeds up reactions without changing the produced substances
54
A Metabolic pathway
is?
Metabolic pathway is the sequence of enzyme-controlled reactions
55
Specifity is when enzymes are what?
Specifity is when enzymes are only able to catalyse specific reactions
56
A Substrate Is?
A substrate is the molecule(s) the enzyme acts on
57
Each enzyme has a specific what?
Each enzyme has a specific role
58
Cells require hundreds of what to survive and function?
Cells require hundreds of biochemical reactions to survive and function?
59
Enzymes lower activation energy by forming what?
Enzymes lower activation energy by forming enzyme/substrate complexes
60
Catabolic reactions are reactions that break down molecules.
In catabolic reactions, what happens?
In catabolic reactions, the enzyme active site affects the bonds in substrates, so that they are easier to break
61
Anabolic reactions are reactions that build up molecules.
In anabolic reactions, what happens?
In anabolic reactions, enzymes bring the substrate molecules together
62
The lock and key hypothesis, the old model, assumes what?
The lock and key hypothesis, the old model, assumes that the active site of an enzyme is rigid in its shape
63
The lock and key hypothesis, the old model, assumes that the active site of an enzyme is rigid in its shape.
However, what indicate that proteins are what?
Crystallographic studies indicate that proteins are flexible
64
When the product leaves the enzyme, what happens?
When the product leaves the enzyme, the active site reverts to its inactive state
65
In order to investigate how enzymes are affected by various factors, we need to be able to do what?
In order to investigate how enzymes are affected by various factors, we need to be able to measure the rate of the reactions they catalyse
66
To measure the progress of an enzyme-catalysed reaction, we usually do what?
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course
67
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for what?
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for a particular event to run its course
68
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
Why does it become difficult for the substrate molecules to come into contact with the enzyme molecules?
There are fewer substrate molecules
Also the product molecules may 'get in the way' of substrate molecules and prevent them from reaching an active site
69
We can measure the change in the rate of a reaction at any point on the curve of a graph by doing what?
We can measure the change in the rate of a reaction at any point on the curve of a graph by measuring the gradient at our chosen point
70
Rate is always expressed how?
Rate is always expressed per unit time
71
The active site and the substrate are not 'the same.'
The correct term is:
The correct term is complementary
72
The effect of temperature on enzyme action:
| A rise in temperature does what?
A rise in temperature increases the kinetic energy of molecules
73
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules do what?
1. Move around more rapidly
| 2. Collide with each other more often
74
At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether.
It is said to be what?
De-natured
75
Denaturation is a permanent change and, once it has occurred, the enzyme does not what?
Denaturation is a permanent change and, once it has occurred, the enzyme does not function again
76
The effect of temperature on enzyme action:
Is there an optimum temperature?
The optimum working temperature differs from enzyme to enzyme
77
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Why isn't our body temp 40 degrees then?
Extra temp = extra calories!
Other proteins, apart from enzymes, may be denatured at higher temperatures
At higher temperatures, any further rise in temperature, for example during illness, might denature the enzymes
78
What is the pH of a solution?
The pH of a solution is a measure of its hydrogen ion concentration
79
Each enzyme has an optimum pH.
What does this mean?
This is a pH at which it works the fastest
80
The effect of pH on enzyme action:
The arrangement of the active site is partly determined by what?
The arrangement of the active site is partly determined by the:
Hydrogen and Ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme
81
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme.
The change in PH affects this enzyme function how?
The change in H+ ions affects the bonding causing the active site to change shape
82
It is important to note that pH fluctuations inside organisms are usually what?
It is important to note that pH fluctuations inside organisms are usually small
83
Low enzyme concentration:
| There are too few what molecules to allow all substrate molecules to do what?
There are too few enzyme molecules to allow all substrate molecules to find an active site at one time
84
As more substrate is added, the active sites gradually become filled, until the point where all of them are working as fast as they can.
The rate of reaction is at its maximum.
After that, the addition of more substrate will have what effect on the rate of reaction?
After that, the addition of more substrate will have no effect on the rate of reaction
When there is an excess of substrate, the rate of reaction levels off
85
The effect of temperature on enzyme action:
| If the temperature goes above a certain level, what break?
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break
86
Pepsin works best at what PH?
2!
87
What are Enzyme inhibitors?
Enzyme inhibitors are substances that:
Directly or Indirectly
interfere with the functioning of the active site of an enzyme
88
There are a number of types of enzyme inhibitors, 2 of which are what?
Competitive and non-competitive inhibitors
89
What do non-competitive inhibitors do?
Non-competitive inhibitors bind to the enzyme at a position other than the active site
90
Competitive inhibitors have a molecular shape similar to what?
Competitive inhibitors have a molecular shape similar to that of the substrate
This allows them to occupy the active site of an enzyme
They therefore compete with the substrate for the available active sites
91
The competitive inhibitor is not permanently bound to the active site and so, when it leaves, what?
The competitive inhibitor is not permanently bound to the active site and so, when it leaves, another molecule can take its place
92
Non-competitive inhibitors attach themselves to the enzyme where?
Non-competitive inhibitors attach themselves to the enzyme at a binding site
93
Non-competitive inhibitors attach themselves to the enzyme at a binding site that is not what?
Non-competitive inhibitors attach themselves to the enzyme at a binding site that is not the active site
94
Metabolism is what....
A series of enzyme controlled reactions
95
All enzymes are....
Proteins
96
All proteins are made up of
Amino acids in a chain (polypeptide) curled into funny shapes
97
Extracellular enzymes are...
Made IN cells and secreted
98
Intracellular enzymes are....
Work WITHIN cells.
99
A good example of an "active site" in a protein?
Heme group in heamaglobin
100
Induced fit means...
That the shape of the active site isn't perfect.. the shape of the protein changes slightly when binding takes place.
101
What will a catalyst do to the activation energy of a reaction?
Lower it
102
Why does temperature changes/ph changes muck up the effectiveness of an enzyme?
Because it changes the shape of the protein. Making it less of a good fit for the substrate.
103
Competitive inhibition is where?
Something binds to the active site and stops a reaction taking place because the substrate can no longer get to the active site.
104
Non-competitive inhibition is where...?
Inhibitor binds somewhere else OTHER than the active site and changes the SHAPE of the protein/active site.
