Enzymes Flashcards
1
Q
What do enzymes need help from to catalyse some reactions
A
Cofactor
2
Q
What part of the enzymes structure is changed if there is a gene mutation
A
Tertiary structure
3
Q
Examples of enzymes catalysing the formation of structural components
A
- collagen in bones
- cartilage
- blood vessel walls
- joints
- connective tissue
4
Q
What two things do enzymes effect
A
-structural
- functional
5
Q
Why is the tertiary structure important in active sites
A
Its shape is complementary to the shape of the substrate molecule
6
Q
What can change the shape of an active site
A
- temperature
- pH
- anything that affects the bonds that hold proteins in the tertiary structure
7
Q
Where do enzymes work
A
- intracellular reactions
- extracellular reactions
8
Q
What is a metabolic pathway
A
A series of consecutive reactions
- every part is catalysed by a specific enzyme
- these produce a specific product
- these then act as substrates for the next reaction (metabolites)
9
Q
What is a catabolic in metabolic pathways
A
Metabolites are broken down to smaller molecules and release energy
10
Q
What is an anabolic in metabolic pathways
A
Energy is used to synthesise larger molecules from smaller ones
11
Q
Example of a metabolic pathway
A
- respiration
- photosynthesis
12
Q
What is catalase
A
An enzyme that protects cels from damage by reactive oxygen
- quickly breaks hydrogen peroxide into water and oxygen
13
Q
What is the structure and characteristics of catalase
A
- four polypeptide chains
- contains a harm group with iron
- fastest acting enzyme
- eukaryotic cells: found in small vesicles called peroxisomes
- white blood cells use them to help kill microbes
14
Q
Example of an extracellular enzyme
A
- amylase
- trypsin
15
Q
What is amylase
A
- produced in the salivary glands
- digests the polysaccharide starch to the disaccharide maltose
- made in the pancreas
- catalyses same reaction as the lumen of the small intestine
16
Q
What is trypsin
A
- made in the pancreas
- acts in the lumen of the small intestine
- digests proteins into smaller peptides
- hydrolyses peptide bonds
17
Q
What is a cofactor
A
- substrate that has to be present to ensure that an enzyme catalysed reaction takes place at the appropriate rate
- some cofactors (prosthetic groups) are part of the enzyme structure
- others (coenzymes) form temporary associations with the enzyme
18
Q
What is a prosthetic group
A
A cofactor that is permanently bound, covalent bonds, to an enzyme molecule
19
Q
What is an enzyme-substrate complex
A
Complex formed by temporary bonding of enzyme and substrate come culex’s during an enzyme catalysed reaction
20
Q
What is the benefit of enzyme substrate complexes
A
Increases rate of reaction
21
Q
What is a co-substrate
A
When they bind to the substrate to form the correct shape to bind to the active site
22
Q
What is a coenzymes
A
Small organic non-proteins molecules that bind temporarily to the active site
- chemically charged during the reaction
23
Q
What happens to a substrate if it is heated
A
- extra energy causes the molecules to move faster
- increased rate of collisions between molecules
- increased force at which they collide
24
Q
What happens if the reactant mixture containing enzymes and substrate molecules is heated
A
- both molecules will gain kinetic energy
- increased rate of successful collisions
- rate of formations of ES complexes increases
- increased rate of reaction
- at a certain temp (optimum temperature) rate of reaction is at its max
25
What does vibrations lead to in molecules
- break some of the weak bonds: hold the tertiary structure of the active site
- active site changes = substrate cannot fit
- temp increases the active site will completely and irreversibly change
- enzyme is denatured
26
Formula to work out rate of reaction
Rate of reaction = 1 / time taken to reach end point
27
What is the units for rate of reaction
S -1
28
What is the temperature coefficient (Q10)
The increase in the rate of process when the temperature is increased by 10 C
29
What is the equation for temperature coefficient
Q10 = rate of reaction at (T+10)C / rate of reaction at T
30
What does it mean if the Q10 is 2
Every 10C the reaction is doubled
31
What is an enzyme product complex
Enzyme molecule with product molecules in its active site
- the two are joined temporarily by non-covalent forced
32
What are the steps of the lock and key theory
- substrate molecule bind to the active site of the enzyme
- temporary hydrogen bonds hold them together
- this forms a ES complex
- substrate is broken into smaller products and leave
- substrate molecules fit in the active site (ES complex)
- bonds form to create an enzyme product complex
- larger molecule leaves the active site
33
What is the induced fit hypothesis
Explains how the transition state (ES complex) is formed
34
Who suggested the induced fit hypothesis
Daniel Koshland (1958)
35
What did Daniel Koshland suggest
Steps of the induced fit hypothesis
- when the substrate fits into the active site it changed shape to mould around the molecule
- when binding the changes of the side chains (R groups) of amino acids give a more precise shape
- moulding allows the substrate to bind more effectively
- ES complex is formed with non-covalent forces binding the substrate to the active site
- an EP complex is formed
- products detach from the active site as they have a slightly different shape
- enzyme can now catalyse other reactions
36
What is the equation for showing how an enzyme catalyses a reaction
Enzyme + substrate —> enzyme-substrate complex —> enzyme product complex —> enzyme + product
E+S ESC EPC E+P
37
Do enzymes lower or increase the activation energy
Lower
38
What is activation energy
the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction
39
How are enzymes able to lower the activation energy
- bring the substrate molecules close enough together to react
- increase chance of molecules binding
- speed up metabolic reactions
40
What is pH
Concentration of hydrogen ions in a solution
41
What is a buffer
Something that resists changes in pH
42
What are buffers able to
Donate or accept hydrogen ions
43
How do changes in pH affect bonds within molecules
- hydrogen ions (proton, + charge)
- excess hydrogen ions will interfere with these hydrogen bonds so the active site will change shape
- this will decreases the rate of reaction
- increased concentration of hydrogen ions will also alter the charged
- more protons will cluster around negatively charged groups
- this interferes with the binding of the substrate and active site
44
Do enzymes work within a narrow or wise range of pH
Narrow
45
What happens if there are small changes around the optimum pH
Slow down the rate of reaction
- shape of the active site is disrupted
46
What happens if the normal pH is restored
Hydrogen bonds can re-form and the active site’s shape is restored
47
True or false
All enzymes have the same optimum pH
False
48
Why does the rate of reaction increase as substrate concentration is increased
- more ES complexes can form
- more products are formed
- it then becomes the limiting factor
49
What happens when substrate concentration is the limiting factor
- all the enzymes active sites are occupied with substrate molecules
- if more substrate is added they cannot successfully collide with and fit into the active site
50
What does the graph for substrate/enzyme concentration against initial rate of reaction look like
- steep gradient
- substrate concentration becomes limiting factor
- line plateaus
51
What controles enzyme synthesis
- cells needs
- genes for synthesis will be turned on or of
52
What is the advantage of enzyme degrading
- eliminated abnormally shaped proteins that might build up and harm the cell
- regulation of metabolism in the cell by eliminating any superfluous (surplus to requirements) enzymes
53
What happens as enzyme concentration is increased
- more active sites available
- more successful collisions between enzyme and substrate
- more ES complexed can form
- so increased rate of reaction
- will later become the limiting factor
54
What happens if enzyme concentration becomes the limiting factor
- there will be no more substrate to bind with the active sites
55
Why is the initial rate of reaction always the greatest
- there is a greater chance of the substrate molecules successfully colliding with an active site
56
Why does initial rate of reaction slow down over time
- the substrate then become product molecules and decreases the substrate concentration
- frequency of collisions decreased
- slows down rate of reaction
57
What is a competitive inhibitor
Substances whose molecules have simular shapes to an enzymes substrate molecules
- they compete with the substrate for the active site
- blocks the site and prevents the formation of ES complexes
58
What is an inhibitor
A substance that reduces or stops reactions
59
What does a competitive inhibitor do
- compete directly with substrate molecules for the active site
- make the enzyme inactive
- when in the active site they cannot be changed
- stops ES and EP complexes from forming
60
What are the different types of enzyme inhibition
- competitive
- non competitive
- reversible
- irreversible
61
What is an inactivator
When a competitive inhibitor binds irreversible to an active site
62
What is non-competitive inhibition
When the inhibition molecule binds to the enzymes somewhere other than the active site
63
How does non-competitive inhibition work
- attach to the enzyme in the allosteric site
- this distrusts the enzymes tertiary structure and shape
- changes the shape of the active site
- max rate of reaction is reduced
64
What is the place where the inhibitor binds to in non-competitive inhibition called
Allosteric site
65
What does the allosteric site do
Disrupts the enzymes tertiary structure and shape
- changes shape of active site
66
What is end product inhibition
When the reaction is finished the products may stay tightly bound to the enzyme
- engulfed cannot form more of the product than the cell needs
67
How are metabolic sequences controlled
- product of one reaction becomes the substrate of the next
- bindings change the shape of enzymes 1s active site
- when concentrations change the inhibitor will leave the enzyme to allow more of the product to be formed
68
What does cyanide inhibit
Aerobic respiration
69
What does snake venom inhibit
Acetylcholinesterase
- important in neuromuscular synapses
70
What does aspirin do
- catalyses the formation of prostaglandins
- reduces risk of blood clots
71
What do ATPase inhibitors do
Inhibit sodium potassium pump
- allows more calcium ions to enter the cells
- increase muscle contraction
- strengthens the heartbeat
72
What do ACE inhibitors do
Inhibit angiotensin converting enzyme (ACE)
- operates in a metabolic pathways that increased blood pressure
- lower blood pressure for hypertension when can’t take beta blockers
- treat heart failure
- minimise second heart attacks
