4 - Enzymes š½ Flashcards
(124 cards)
1
Q
Enzymes areā¦
A
biological catalysts
2
Q
What type of proteins are enzymes?
A
Globular
3
Q
What causes enzymes to react at faster rates?
A
Interacting with substrate molecules
4
Q
What is an anabolic reaction?
A
Building up thinhs
5
Q
What is a catabolic reaction?
A
Breaking down reactions
6
Q
What do enzymes catalyse in food?
A
Digestion
7
Q
Define metabolism
A
The sun of all of the different reactions and reaction pathways happening in a cell or an organism
8
Q
What is the certain point called that enzymes can increase the rate of reactions up to?
A
Vmax (max initial velocity)
9
Q
The specificity of an enzyme
A
Each enzyme catalyses one biochemical reaction
10
Q
What is the activation energy?
A
The energy needed to be supplied for most reactions to start
11
Q
How do enzymes help reduce the activation energy needed?
A
Enzymes help the molecules collide successfully
12
Q
What is the active site?
A
An area within the 3Y of the enzyme with a shape complementary to the specific substrate
13
Q
When the substrate is bound to the active site, what is formed?
A
Enzyme-substrate complex
14
Q
When the substrates react, the products are formed inā¦
A
An enzyme-product complex
15
Q
How is the substrate held?
A
In such a way that the right atom-groups are close enough to react
16
Q
How are temporary bonds formed in an enzyme / substrate?
A
The R-groups within the active site of the enzyme will interact with the substrate
17
Q
How do temporary bonds help a reaction along?
A
By putting strain on the bonds within the substrate
18
Q
What is the induced-fit hypothesis?
A
The active site of the enzyme changed shape slightly as the substrate enters
19
Q
What is the initial intereaction between enzyme/substrate in induced-fit?
A
Weak initial interaction
20
Q
How do the weak interactions rapidly change in induced-fit?
A
Induces changes in the enzymes 3Y that strengthen the binding, putting strain on the substrate molecule
21
Q
How does putting strain on the substrate effect the reaction in induced-fit?
A
This weakens a particular bond(s) in the substrate, therefore lowering the activation energy
22
Q
What does catalase do?
A
Breaks down hydrogen peroxide into water and oxygen quickly, preventing its accumulation
23
Q
Where is catalase found?
A
In both plant and animal tissues
24
Q
What is the purpose of most
extracellular enzymes?
A
Released from cells to break down large nutrients into smaller molecules that can enter the cell-surface membrane
25
What type of organisms need extracellular enzymes?
Both single-celled and multi-cellular to make use of polymers for nutrition
26
Where do single felled organisms release their extracellular enzymes?
Directly into their surroundings
27
How are extracellular organisms used in multicellular organisms?
Nutrients are taken in by food, but need to be digested into smaller molecules to be absorbed into the bloodstream
28
Digestion of starch
What does amylase do?
Starch polymers are partially broken down into maltose (disaccharide)
29
Digestion of Starch
Where is amylase produced?
By the salivary glands and the pancreas
30
Digestion of Starch
Where is amylase released?
In saliva in the mouth or in pancreatic juice into the small intestine
31
Digestion of starch
How is maltose then broken down into glucose (monosaccharide)?
By maltase found in the small intestine
32
Digestion of starch
Why are amylase and maltase needed to turn starch into glucose?
Itās small enough to be absorbed by the cells lining the digestive system and then into bloodstream
33
Digestion of proteins
What is trypsin?
A protease
34
Digestion of proteins
What are proteases?
A type of enzymes that catalyses the digestion of proteins into smaller peptides, which can then be broken down further into amino acids
35
Digestion of proteins
Where is trypsin produced and found?
Produced in the pancreas and released with the pancreatic juice into the small intestine
36
Why is it important reactions donāt happen too fast?
Leads to a build up of excess products
37
What controls the different steps in reaction enzymes?
Different enzymes
38
What regulates the rate and quantity of product formation?
Controlling the activity of enzymes at crucial points
39
What activates enzymes?
Cofactors
40
What inactivates enzymes?
Inhibitors
41
What are inhibitors?
Molecules that prevent enzymes from carrying out their normal function of catalysis
42
What are the two types of inhibitors?
Competitive and non-competitive
43
Competitive inhibition
Step 1 = a molecule or part of a molecule that has a similarā¦
shape to the substrate of an enzyme can fit into that active sit of the enzyme
44
Competitive Inhibition
Step 2 = this blocks the substrate from enteringā¦
the active site, preventing the enzyme from catalysing the reaction
45
Competitive Inhibition
Step 3 = the enzyme cannot carry outā¦
itās function and is said to be inhibited
46
Competitive Inhibition
Step 4 = what is the non-substrate molecule that binds to the active site?
A type of inhibitor
47
Competitive Inhibition
Step 4 = substrate and inhibitor molecules present in a solution will competeā¦
to bind to the active sites of the enzymes catalysing the reaction
48
Competitive Inhibition
Step 5 = this will reduce the number ofā¦
substrate molecules binding to the active sites in a given time and slows down the rate of reaction
49
Competitive Inhibition
How do most competitive inhibitors bind to the active site?
Temporarily so their effect is reversible
50
Competition Inhibition
What does the degree of inhibition depend on?
Relative concentrations of substrate, inhibitor and enzyme
51
Competitive Inhibition
What is an exception to the temporary binding to the active site?
Aspirin
52
Competitive Inhibition
What is their effect of rate of reaction?
Reduces
53
Competitive Inhibition
What is their effect on the Vmax?
Doesnāt change it of the enzyme it inhibits
54
Competitive Inhibition
What inhibitor of an enzyme is used in the synthesis of cholesterol?
Statins
55
What can high blood cholesterol levels cause?
Heart disease
56
Competitive Inhibition
What active site does aspirin irreversibly inhibit?
COX enzymes, preventing the synthesis of prostaglandins and thromboxane = the chemicals responsible for producing pain and fever
57
Non-competitive Inhibition
Step 1 = the inhibitor binds to the enzyme atā¦
a location other than the active site - this location is called the allosteric site
58
Non-competitive Inhibition
Step 2 = the binding of the inhibitor causesā¦
3Y of the enzyme to change, meaning the active site changes shape
59
Non-competitive Inhibition
Step 3 = this results in the active site no longer having aā¦
complementary shape to the substrate so it is unable to bind to the enzyme
60
Non-competitive Inhibition
Step 4 = the enzyme cannot carry out itsā¦
function and is said to be inhibited
61
Why is it called non-competitive inhibition?
The inhibitor doesnāt compete with the substrate for the active site
62
Non-competitive Inhibition
What does increasing the concentration of inhibitor do to rate?
Decrease it as more active sites are unavailable
63
Organophosphates are used as what?
Insecticide or herbicides
64
What do organophosphates do?
Irreversibly inhibit the enzyme acetyl cholinesterase
65
What does acetyl cholinesterase do?
Necessary for nerve impulse transmission
66
What does the absence of acetyl cholinesterase do?
Leads to muscle cramps, paralysis and even death if accidentally inhested
67
What is used to treat long term indigestion?
Proton pump inhibitors (PPIs)
68
What do PPIs do?
Irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach
69
What are PPIs effective at?
Reducing the production of excess acid, which can lead to stomach ulcers
70
Define end-product inhibition
The term used for enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it
71
What does end-product inhibition serve as?
A negative feedback control mechanism for reactions so excess products are not made and resources arenāt wasted
72
What is end-product inhibition:
Competitive or non-competitive?
Non-competitive
73
What is respiration?
A metabolic pathway resulting in the production of ATP
74
How is glucose broken down in respiration?
- addition of two phosphate groups to glucose
- addition of second group results in intial breakdown
75
What enzyme catalyses the addition of a phosphate group to break down glucose?
Phosphofructokinase (PFK)
This enzyme is inhibited by ATP
76
What happens when ATP levels are high?
More ATP binds to PFK, preventing the addition of the second phosphate to glucose so it isnāt broken down and ATP isnāt produced at the same raye
77
What happens as ATP is used up?
Less ATP binds to PFK and the enzyme catalyses the addition of the second phosphate to glucose, resuming respiration and the production of ATP
78
Define a cofactor
A non-protein component or metallic ion that is required for an enzymes activity as a catalyst
79
Cofactors can be considered what?
āHelper moleculesā that assist in biochemical transformations
80
Cofactor = Zn++
Enzyme/protein = ?
- Carbonic anhydrase
- alcohol dehydrogenase
81
Cofactor = Fe++ or Fe+++
Enzyme/protein = ?
- cytochromes
- haemoglobin
- ferredoxin
82
Cofactor = Cu++ or Cu+
Enzyme/protein = ?
Cytochrome oxidase
83
Cofactor = K+ or Mg++
Enzyme/protein = ?
Pyruvate phosphokinase
84
What is vitamin B3 used to synthesise?
NAD and NADP
85
What does NAD do?
A coenzyme responsible for transfer of hydrogen atoms between molecules involved in respiration
86
What do NADP do?
Similar as NAD but in photosynthesis
87
What does vitamin B5 synthesis?
Coenzyme A
88
What does coenzyme A do?
Breakdown fatty acids and carbohydrates in respiration
89
What are prosthetic groups?
Cofactors as they are required got certain enzymes to carry out their catalytic function
90
How do prosthetic groups add to the structure of proteins?
Tightly bound and form a permanent feature
91
What are inactive enzymes called?
Inactive precursor enzymes
92
What do inactive precursor enzymes tend to do?
Cause damage within cell producing them or to tissues once released
93
How are precursor enzymes activated?
Undergo a change in shape (3Y) particularly to the active site
94
What must be added to activate a precursor enzyme?
A cofactor
95
Define an apoenzyme
An inactive precursor enzyme without its non-protein part (cofactor)
96
Define a holoenzyme
The active enzyme with its cofactor added
97
Cofactor =
Non-protein part is a metal ion
98
Coenzyme =
A small organic molecule
99
What external influences can result in a change in 3Y and activate a precursor enzyme?
Changes in conditions such as pH or temperature
100
What type of precursor enzymes are produced when they are activated by external conditions?
Zymogens or proenzymes
101
What happens when inactive pepsinogen is released into the stomach to digest proteins?
The acid pH brings about the transformation into the active enzyme pepsin
This adaption protects the body tissues against the digestive action of pepsin
102
Factors Affecting Enzyme Activity
Increase in temperature = increased frequency ofā¦
ā¦successful collisions between substrate and enzyme = increased rate of reaction
103
Factors Affecting Enzyme Activity
Define the temperature coefficient
A measure of how much the rate of a reaction increases with a 10Ā°C temperature increase
104
Factors Affecting Enzyme Activity
What is the symbol for the temperature coefficient?
Q10
105
Factors Affecting Enzyme Activity
What is the Q10 for enzyme-controlled reactions?
2 as the rate of reaction doubled with a 10Ā°C temp increase
106
Factors Affecting Enzyme Activity
What happens do the bonds holding proteins together at a higher temp?
They vibrate more = bonds break = change in precise 3Y = denature
107
Factors Affecting Enzyme Activity
What happens when an enzyme denatures?
The enzyme is no longer complementary to the substrate
108
Factors Affecting Enzyme Activity
Define the optimum temperature
The temp at which the enzyme has the highest rate of activity
109
Factors Affecting Enzyme Activity
What is the optimum temp in humans?
40Ā°C
110
Factors Affecting Enzyme Activity
What is thermophilic enzymes optimum temp?
70Ā°C
111
Factors Affecting Enzyme Activity
What is psychrophillic enzymes optimum temp?
Below 5Ā°C
112
Factors Affecting Enzyme Activity
What happens to rate with enzymes that have denatured below optimum temp?
decrease is rate as they havenāt denatured but are just less active
113
Factors Affecting Enzyme Activity
Enzymes adapted to cold will have what properties?
- more flexible
- less stable
- smaller temp changes will denature then
114
Factors Affecting Enzyme Activity
Define the optimum pH
The active site will only be at the right shape at a certain hydrogen ions concentration
115
Factors Affecting Enzyme Activity
If the pH changed and denatured enzyme, but then changed back, what will happen?
The enzyme will go back to the correct shape = renaturation
116
Factors Affecting Enzyme Activity
What happens if pH is changed significantly?
Structure of the enzyme will be irreversibly altered
117
Factors Affecting Enzyme Activity
pH hydrogen ions interact with what, and what causes a change in this interaction?
Polar and charged R-groups
- changing the conc of H+ ions will change the degree of the interactive
118
Factors Affecting Enzyme Activity
A low pH means lots of H+ ions =
The less the R-groups are able to interact with each other = bonds break = enzyme changes shape
(Same with high pH)
119
Factors Affecting Enzyme Activity
Which factor is rarely limiting?
Substrate and enzyme concentration
120
Factors Affecting Enzyme Activity
What happens when there is an increased number of substrate particles?
Higher collision rates with the active site of enzymes = increasing rate
121
Factors Affecting Enzyme Activity
How can you increase the available active sites?
Increase the enzyme concentration
122
Factors Affecting Enzyme Activity
What is the Vmax?
The rate of reaction is at its maximun
123
Factors Affecting Enzyme Activity
What causes a Vmax?
All active sites are occupied by substrate particles and no more enzyme-substrate complexes can be formed until products are released from the active sites
124
Factors Affecting Enzyme Activity
Is the rate of reaction directly proportional to enzyme conc?
Yes
