Unit 1.4 - Biological reactions are regulated by enzymes Flashcards
What is the shape of an enzyme and why?
3D spherical, globular shape
Polypeptide chain is folded back on itself
Which protein structure do enzymes have?
Tertiary
What causes the 3D spherical globular shape of an enzyme?
Polypeptide chain folding back on itself
What does the polypeptide chain folding back on itself cause for an enzyme?
Gives it its 3D spherical globular shape
What combines with an enzymes active site to form a product?
Substrate molecules
What do substrate molecules combine with on an enzyme to form a product?
Active site
What happens when a substrate combines with the active site of an enzyme?
A product forms
What can enzymes be described as?
Biological catalysts
What does the fact that enzymes are biological catalysts mean?
They speed up the rate of chemical reactions without undergoing permanent change
What number is high for enzymes?
High turnover number
High turnover number
Enzymes work efficiently to convert many substrate molecules of substrate into product per unit time
What does the fact that enzymes work efficiently to convert many substrate molecules of substrate into product per unit time mean?
They have a high turnover number
Why do enzyme reactions need to happen quickly?
To respond to changes in Environment
What do changes in Environment mean that enzymes have to?
Enzyme reactions need to happen quickly to respond to these changes
Where can enzymes react?
Inside or outside of the cell
Enzymes that react inside the cell
intracellular
Intercellular enzymes
Are synthesised and are active within the cell
Enzymes that act outside the cell
Extracellular
Extracellular enzymes
Synthesised within cells but are active outside
What’s similar and different between intercellular and extracellular enzymes?
Both - are synthesised within cells
Intercellular - are active inside the cell
Extracellular - are active outside the cell
Extracellular enzyme example
Digestive enzymes
What are digestive enzymes an example of?
Extracellular enzymes
Example of intercellular enzymes
Enzymes of respiration
What are enzymes of respiration examples of?
Intercellular enzymes
What is required in order for a reaction to occur?
Activation energy
What is activation energy required for?
A reaction to occur
What do enzymes enable reactions to do?
Occur at lower activation energies, so that they can occur at high rates even at relatively low temperatures
What do enzymes do to the activation energy of a reaction and what does this mean?
Lower the activation energy of a reaction
Chemical reactions can occur at high rates even at relatively low temperatures
Why is a reaction having a low activation energy good?
It can occur at high rates even at relatively low temperatures
What causes a chemical reaction to occur at high rates even at relatively low temperatures?
Enzymes lowering the activation energy of a reaction
Metabolism
All reactions that occur in the body
What’s the name for all reactions that occur in the body?
Metabolism
What do metabolism reactions occur in?
Sequences called metabolic pathways
Metabolic pathways
Metabolism reactions occur in these sequences
What are two types of metabolic reactions?
Anabolic
Catabolic
What are anabolic and catabolic reactions examples of?
Metabolic reactions
Anabolic reactions
Building up molecules
Type of reaction for building up molecules
Anabolic
Catabolic reactions
Molecules are broken down
Type of reaction when molecules are broken down
Catabolic
2 examples of anabolic reactions
Protein synthesis (amino acids in a chain form a polypeptide)
Condensation
What is protein synthesis an example of?
An anabolic reaction
What is condensation an example of?
An anabolic reaction
2 examples of catabolic reactions
Digestion
Hydrolysis
What is digestion an example of?
A catabolic reaction
What is hydrolysis an example of?
A catabolic reaction
What happens to the products of enzyme-controlled reactions?
Become a reactant in the next reaction
What is the reactant of an enzyme-controlled reaction?
A product of a different enzyme-controlled reaction
What type of reaction uses products to become reactants in the next reaction?
Enzyme-controlled reactions
Name three parts involved in a simple metabolic pathway
Substrate
Intermediate
Product
Example of a metabolic pathway
Glycolysis
What’s glycolysis an example of?
A metabolic pathway
Glycolysis
The start of cellular respiration - the way cells release energy
What’s glycolysis?
The start of cellular respiration - the way cells release energy
(Example of a metabolic pathway)
Which process is the start of cellular respiration - the way cells release energy?
Glycolysis
What do metabolic reactions occur as?
A series of small steps
What occurs in a series of small steps?
Metabolic reactions
What is each step in a metabolic reaction?
A reaction catalysed by an enzyme due to the active site containing reactive molecules
Is each step of a metabolic reactions catalysed by the same enzyme?
No - a different enzyme (lots of different types in the cell)
What do different enzymes within a cell do?
Catalyse different steps within the metabolic reaction
What does each individual enzyme react with?
A particular substrate molecule
How can we describe each individual enzyme?
Specific (to a particular substrate molecule)
What does the fact that enzymes react to a particular substrate molecule make it?
Specific
Why are enzymes specific?
Each one reactions with a particular substrate molecule
Describe the relationship between the shape of the active site and a substrate molecule
Complementary (not the same!)
What shape is the active site of an enzyme?
3D and globular
Is an active site’s shape the same as the substrate molecule?
No - its complementary
What’s the 3D globular shape of the active site of an enzyme maintained by?
Tertiary protein bonding
What is maintained by tertiary bonding on an enzyme?
The 3D globular shape of the active site
What’s the first stage to how enzymes work?
Substrate and enzyme collide successfully
What happens once a substrate has collided successfully with an enzyme?
Substrate fits into and binds to the active site by interactions with R groups/polar atoms of the amino acids that make up the active site to form an enzyme-substrate complex
How is an enzyme-substrate complex formed?
When the substrate fits into and binds to the active site of an enzyme by interactions with R groups/polar atoms of the amino acids that make up the active site
What forms when a substrate has bonded to the active site of an enzyme?
Enzyme-substrate complex
What makes up the active site of an enzyme?
R groups/polar atoms of amino acids
How does a substrate bind to the active site of an enzyme?
Interactions with R groups/polar atoms of the amino acids that make up the active site
Which part of the enzyme do we call the enzyme-substrate complex?
The entire enzyme, with the substrate binded to it
What is the ability of R groups and the substrate to form bonds affected by?
Temperature and pH
What does temperature and pH affect the ability of?
R groups and the substrates ability to form bonds
How are the bonds in the substrate broken in the active site of an enzyme?
They’re distorted, which puts strain on the bonds that are going to be broken and increase the chance that they’ll break
What are distorted in order to put strain on the so that they break?
The bonds in a substrate
What does breaking the bonds of a substrate do?
Brings new atoms in the substrates closer together so that new bonds can form
How do new bonds form within the substrate to form a product?
Breaking the bonds brings new atoms in the substrates closer together so that new bonds an form
What are the two theories of enzyme action?
Lock and key hypothesis
Induced fit model
What does the original enzyme hypothesis suggest?
The lock and key hypothesis suggests there’s an exact fit between the substance and the active site of an enzyme
Which enzyme hypothesis suggests there’s an exact fit between the substance and the active site of an enzyme?
Lock and key hypothesis
What’s the lock and key hypothesis supported by?
X-ray diffraction studies of enzyme molecules
What has X-ray diffraction studies of enzyme molecules supported?
The lock and key hypothesis
What type of metabolic reaction is an enzyme turning a substrate into a product? Why?
Anabolic - it involves enzyme building
What are the two types of complex generated during an enzyme catalysing a substrate?
- Enzyme-substrate complex
- Enzyme-product complex
Where does a substrate react and form a product?
Whilst still in the active site
What holds the substrate molecule and why?
The active site of the enzyme to release activation energy and speed up the process
Anabolic enzymes
Build larger products from smaller substrate molecules
Which type of enzymes build larger products from smaller substrate molecules?
Anabolic enzymes
Catabolic enzymes
Break large substrate molecules into smaller products
What type of enzymes break large substrate molecules into smaller products?
Catabolic enzymes
What happens with the induced fit model?
The enzyme molecule changes shape as the substrate molecules get close - the change in shape is ‘induced’ by the approaching substrate molecule
What changes shape in the induced fit model and how?
The enzyme molecule, as it’s “induced” by the approaching substrate molecule
What does the induced fit model rely on?
The fact that molecules are flexible because single covalent bonds are free to rotate
Why are molecules flexible?
Single covalent bonds are free to rotate
What does the induced fit model explain?
The ability of some enzymes that have a wide range of specificy, that can catalyse more than one substrate, due to the ability of the substrates to mould it
What does the fact that some enzymes can catalyse more than one substrate give them?
A wide range of specificy
Why do some enzymes ave a wide range of specificy?
They can catalyse more than one substrate due to the ability of the substrates to mould it
Two examples of enzymes with broad specificy
Lipase
Lysozyme
What are lipase and lysozyme examples of?
Enzymes with broad specificy
Where’s lipase found?
saliva, stomach, pancreas
What’s found in the saliva, stomach and pancreas?
The enzyme lipase
What does the enzyme lipase do?
Breaks down fats in food so that they can be absorbed in the intestines
Which enzyme breaks down fats in food so that they can be absorbed in the intestines?
Lipase
Where is the enzyme lysozyme found?
Tears
Saliva
How does lysozyme work?
Cleaves the peptidoglycan component of bacterial cell walls
Binds to and breaks down the polysaccharide coating of a bacterial cell, leading to cell death
Which enzyme binds to and breaks down the polysaccharide coating of a bacterial cell, leading to cell death?
Lysozyme
How is lysozyme an example of an enzyme with a wide range of specificy and therefore backs up the induced fit model?
The bacterial cells being destroyed have a wide range of cell walls and structures, so the induce fit model could explain this broad specificy
Lysozymes break down bacteria, yet they have a wide range of cell walls and structures, so which model explains this?
The induced fit model, as this could explain the broad specificity of the lysozyme enzyme
What are the Environmental factors that effect the rate of enzyme catalysed reaction?
Temperature
pH
Substrate concentration
Enzyme concentration
What do the environmental factors - temperature, pH, substrate concentration and enzyme concentration - effect?
the rate of enzyme catalysed reaction
What happens between 0 degrees and optimum temperature in terms of enzyme catalysed reaction?
Increasing kinetic energy
Molecules move about me quickly
More collisions between them
Probability of successful collisions between the substrate and the active site of the enzyme to catalyse the reaction and form enzyme-substrate complexes/products increases
What do higher temperatures give enzymes and what does this cause?
Kinetic energy - molecules more about more quickly and there’s more collisions between them
The probability of successful collisions between substrate and the active site of the enzyme to catalyse the reaction and form an enzyme-substrate complex increases
What is formed following successful collision between an enzyme and a substrate?
An enzyme-substrate complex
What causes an enzyme-substrate complex to form?
Successful collisions between enzymes and substrates
What happens to the enzyme above optimum temperature?
High kinetic energy causes irreversible changes to the shape of the active site
When are irreversible changes caused to the active site of an enzyme and what causes this?
When temperatures go above optimum for that enzyme
Kinetic energy
How is irreversible damage caused to the shape of the active site of an enzyme in temperatures above optimum?
High kinetic energy causes atoms to vibrate which breaks bonds
At which point are irreversible changes caused to the shape of an enzyme’s active site?
Past optimum for that enzyme
How are the bonds in an enzyme’s active site broken?
When temperatures rise above optimum for that enzyme, and kinetic energy causes atoms to vibrate and this breaks the bonds
Which bonds are broken on an enzyme’s active site when temperatures rise above optimum for that enzyme?
The bonds which maintain the tertiary structure of the enzyme
Hydrogen bonds, ionic bonds, disulphide bonds (covalent)
When are the bonds which maintain the tertiary structure of an enzyme broken?
When temperatures rise above optimum for that enzyme
What happens when the bonds which maintain the tertiary structure of an enzyme are broken?
The substrate cannot fit into the active site (is no longer complementary) - the enzyme cannot continue to catalyse the reaction and has been denatured
When has an enzyme been denatured?
When the temperatures have risen above optimum for that enzyme and the bonds which maintain the tertiary structure of the enzyme have been broken
What happens to a substrate molecule when approaching the active site of an enzyme that has been denatured?
Substrate molecule cannot fit into the active site
Enzyme cannot continue to catalyse the reaction and has been denatured
Describe the active site of an enzyme when a substrate molecule can no longer fit into it due to it being denatured
No longer complementary
What’s it important to always refer to when giving reasons for why an enzyme catalysed reaction has been effected in a certain way?
Kinetic energy
Collisions
Enzyme-substrate complexes/products
What’s the order in which the bonds break in the tertiary structure of an enzyme? Why?
Hydrogen bonds (weakest)
Ionic bonds
Disulphide bonds (covalent - strongest)
Which is the strongest of the bonds in the tertiary protein structure? Why?
Disulphide bonds, which are covalent
Which of the bonds in the tertiary protein structure are weakest?
Hydrogen bonds
Which enzymes tend to be more stable at high temperatures?
Enzymes with lots of disulphide bonds
What do enzymes with lots of disulphide bonds tend to be more than other enzymes? Why?
More stable at higher temperatures - strongest of the bonds in tertiary protein structure
What happens in terms of enzyme catalysed reaction when the temperatures are relatively low?
Product is formed slowly due to low kinetic energy
Fewer vibrations of substrates and enzymes
Less frequent collisions between substrates and active sites to form enzyme-substrate complexes
Enzyme activity is low
Maximum product formation axes time to achieve
Under which conditions does the maximum product formation take time to achieve and why?
Low temperatures
Low kinetic energy = fewer vibrations of substrates and enzymes
Less frequent collisions between substrates and active sites to enzyme-substrate complexes
Enzyme activity is low
Under which conditions is enzyme activity low and why?
Lower temperatures - low kinetic energy
What does low kinetic energy levels due to low temperatures mean in terms of the formation of enzyme-substrate complexes? Why?
Less frequent collisions between substrates and active sites to form enzyme-substrate complexes
What is pepsin and what does it do?
An enzyme that catalyses the break down of proteins in the stomach, where pH is very acidic
Which enzyme catalyses the break down of proteins in the stomach, where pH is very acidic?
Pepsin
Describe the pH of the stomach
Very acidic
What is salivary amylose and what does it do?
A type of enzyme that digests starch to maltose in the mouth (works at a pH slightly higher than 7)
At which pH does salivary amylose work?
Slightly higher than 7
Which enzyme works at a pH slightly higher than 7?
Salivary amylose
Which enzyme digests starch to maltose in the mouth?
Salivary amylose
What type of environment do enzymes always work in?
Solution
Describe the pH range which enzymes have
Very narrow
Do all enzymes have the same pH optima?
No - they all have very different pH ranges which they work in
What explains the fact that the digestive system has different regions?
All enzymes have very different pH ranges which they work in/pH optima
How is the digestive system set out and why?
With different regions as all enzymes have different pH optima
What do small changes in pH within the enzyme’s range do?
Affect the rate of reaction without affecting enzyme structure
Which environmental change affects the rate of reaction for an enzyme but doesn’t affect its structure?
Small changes in pH within the enzymes range
What do small changes outside an enzyme’s optimum range do?
Cause reversible changes in enzyme structure = inactivation
Which environmental condition cause reversible changes in enzyme structure (inactivation)?
Small changes outside the enzyme’s pH range
Reversible changes in enzyme structure caused by small changes outside the pH optimum range
Inactivation
Inactivation
Reversible changes in enzyme stature due to small changes outside the pH optimum range
What do extremes of pH do to an enzyme?
Can denature an enzyme
What can denature an enzyme in terms of pH?
Extremes of pH
How can we keep pH within a range?
Use chemicals which maintain a certain pH = Buffers
What are buffers?
Chemicals which maintain a certain pH in order to keep it in suitable range
How is an enzyme-substrate complex formed in terms of charges?
Charges on the amino acid side chains of the active site must attract charges on the substrate molecule
Which charges must attract each other in order to form an enzyme-substrate complex?
Charges on the amino acid side chains of the active site and the charges on the substrate molecule
What happens when the charges on the amino acid side chains of the active site attract the charges on the substrate molecule?
An enzyme-substrate complex forms
What are the charges on an enzyme’s active site affected by?
Free hydrogen (H+) and hydroxyl (OH-) ions
What do free hydrogen (H+) and hydroxyl (OH-) ions affect?
The charges of the enzyme’s active site
Hydrogen and hydroxyl ions symbols
(H+) and (OH-)
What may happen if the medium in which an enzyme and a substrate is in is too acidic?
Active site and substrate may end up with the same charge and repel one another
Slow down and eventually stop enzyme-substrate complexes from forming
What would cause a substance to be too acidic in terms on ions?
Too many H+ ions
What would too many H+ ions cause a substance to be?
Too acidic
What would cause an active site and a substrate to have the same charge as one another?
Too many H+ ions (too acidic)
What would stop being formed in a solution that’s too acidic and why?
Enzyme-substrate complexes
The active site and the substrate may end up with the same charge and would repel one another instead of attract one another
In which situation would the active site of an enzyme and a substrate molecule repel one another?
When they’re ended up with the same charge, perhaps in a solution that’s too acidic
What would an enzyme and a substrate do if they had the same charge, for example, from being in a solution that’s too acidic?
Repel one another, stopping enzyme-substrate complexes from being able to be formed
Describe the graph that shows the affect of temperature on the rate of enzyme catalysed reaction?
Goes up quickly, slows down a little and then drops down to zero
Vmax meaning
The maximum rate of reaction
The maximum rate of reaction symbol
Vmax
Describe the graph that demonstrates the affect of substrate concentration on enzyme catalysed reactions
Up steadily before flattening off
What is the limiting factor at the start of a ‘substrate concentration’ vs ‘rate of reaction’ graph?
Substrate concentration
What is the limiting factor at the end of a ‘substrate concentration’ vs ‘rate of reaction’ graph?
Enzyme concentration/number of active sites
On which part of a ‘substrate concentration’ vs ‘rate of reaction’ graph is substrate concentration the limiting factor?
The start
On which part of a ‘substrate concentration’ vs ‘rate of reaction’ graph is enzyme/active site concentration the limiting factor?
The end
Something that limits the rate of reaction
Limiting factor
Limiting factors
Something that limits the rate of reaction
What happens to the rate of reaction in terms of the substrate concentration as long as the enzyme concentration remains constant?
The rate of reaction will increase as the substrate concentration increases
What has to remain constant for the rate of reaction to increase as the substrate concentration increases?
Enzyme concnetration
Why does the rate of reaction increase as the substrate concentration increases?
Plenty of free active sites - more likely for a collision between an active site and a substrate to form an enzyme-substrate complex
What happens as the substrate concentration increases and why?
the rate of reaction increases (as long as the enzyme concentration remains constant)
Plenty of free active sites, making it more likely for a collision between an active site and a substrate to form an enzyme-substrate complex
What happens to the rate of reaction after a certain point in terms of substrate concentration and why?
Reaction levels off once all of the active sites are simultaneously occupied - they’re saturated with substrate molecules without free active sites.
Rate of reaction stops increasing - the number of active sites has become a limiting factor.
What’s the phrase for the active sites being simultaneously occupied at higher substrate concentrations?
Saturated with substrate molecules
What are the active sites of enzymes at higher substrate concentrations and what’s the phrase for this?
Simultaneously occupied - saturated with substrate molecules
What becomes a limiting factor after a certain point in terms of substrate concentration and why?
The number of active sites - saturated with substrate molecules
How does the fact that there’s less available active sites at higher substrate concentrations affect the rate of reaction?
Stops increasing, as the probability of a substrate and enzyme colliding to form an enzyme-substrate complex decreases
How does enzyme concentration affect the rate of reaction?
As long as the substrate concentration is in excess and temperature and pH are kept close to optimum, the rate of reaction is in direct proportion to the concentration of enzyme
What would a graph showing ‘enzyme concentration’ vs ‘rate of reaction’ show and why?
A straight line through the axis, as they’re in direct proportion
Which factor is in direct proportion to the rate of reaction of enzymes?
Enzyme concentration
Which conditions have to occur for enzyme concentration to be directly proportional to the rate of reaction?
Temperature and pH close to optimum
Why do higher enzyme concentrations increase the rate of reaction?
The more enzymes, the more free active sites available - higher probability of substrate molecules colliding with them to form enzyme-substrate complexes
Initial rat of reaction
Instantaneous rate at the start of the reaction (t=0)
Factors such as substrate concentration haven’t had time to change
What would we see on a ‘product concentration’ vs ‘time’ graph and why?
Steeper curve at the beginning which levels off
The initial rate of reaction is higher, with the substrate being turned into enzyme-substrate complexes
Less substrate available over time
Probability of successful collisions between enzymes and substrates decreases
Less product forms, due to a reduced rate of enzyme catalysed reaction
What happens to product concentration in terms of enzyme reactions over time and why?
Decreases as less substrate is available over time, so the probability of successful collisions between enzymes and substrates decreases, so less product forms due to a reduced rate of enzyme catalysed reaction
What happens to substrate concentration as a reaction progresses and why?
Falls - it’s converted into product
What happens to the rate of product formation in an enzyme catalysed reaction over time and why?
Decreases as the substrate is used up
What do inhibitors do?
Reduce or even stop the catalytic activity of enzymes in biochemical reactions
What reduce or even stop the catalytic activity of enzymes in biochemical reactions?
Inhibitors
What type of reactions do inhibitors stop catalytic activity within?
Biochemical
What type of enzyme activity do inhibitors reduce or stop in biochemical reactions?
Catalytic activity of enzymes
How do inhibitors inhibit enzyme reactions?
Block or distort (change the shape) of the active site
What blocks or distorts the shape of an active site on an enzyme?
Inhibitors
What are the two types of inhibitors?
Competitive inhibitors
Non-competitive inhibitors
Competitive inhibitors
Occupy active sites and prevent substrate molecules from binding to active sites (“compete” with substrates for active sites)
What occupy active sites and prevent substrate molecules from binding to enzymes?
Competitive inhibitors
(“Compete” with substrates for active sites)
Non-competitive inhibitors
Attach to other parts (not the active site) of an enzyme molecule, perhaps distorting its shape
What attach to other parts (not the active site) of an enzyme molecule, perhaps distorting its shape?
Non-competitive inhibitors
Is the inhibitor within the active site of an enzyme permanent?
No, only a temporary situation
Describe the situation in which a competitive inhibitor is within the active site of an enzyme?
Only temporary
How can a competitive inhibitor enter the active site of an enzyme?
Has a complementary shape
How does a competitive inhibitor reduce or stop the catalytic activity of an enzyme?
Has a complementary shape to the active site, allowing it to block it and prevent reactions from happening and enzyme-substrate complexes from forming
What are prevented from forming as a result of competitive inhibitors?
Enzyme-substrate complexes
What’s the similarity between a competitive inhibitor and a substrate molecule?
Structurally similar
What’s the competitive inhibitor structurally similar to?
The substrate molecule that would fit in the enzyme’s active site
What’s the probability of a substrate or an inhibitor entering the active site of an enzyme when their concentrations are equal?
50:50
Which type of inhibitor has a 50:50 chance of entering the active site against the substrate?
Competitive inhibitors
What has to be kept equal in order for the probability of a substrate and competitive inhibitor to enter an active site to be equal?
Their concentrations
What would an increased concentration of substrate molecules mean for the probability of entering the active site with the presence of competitive inhibitors?
Increased probability of entering the active site
What’s the name of the site the non-competitive inhibitor enters?
Allosteric site
Allosteric site
The site on an enzyme a non-competitive inhibitor enters instead of the active site
Where does a non-competitive inhibitor bind to an enzyme?
Not the active site, but the Allosteric site
How do non-competitive inhibitors reduce or stop the catalytic activity of enzymes in biochemical reactions?
When they bind to the Allosteric site, it prevents the binding of the substrate by changing the shape of the active site
What happen to the active site with non-competitive inhibitors and why?
Changes shape so the substrate in unable to bind with it as the inhibitor combines to the Allosteric site
How can competitive inhibition be reversed?
Increasing the concentration of substrates
Which type of inhibition is reversible?
Both types, but not always non-competitive inhibition
Is non-competitive inhibition reversible?
Usually, not always
What depends on non-competitive inhibition being reversible?
The concentration of inhibitor and substrate
How could the affects of non-competitive inhibition be reversed?
Inhibitor detaches, allowing the enzyme to return to its normal shape for the reaction to continue
If a non-competitive inhibitor detached itself from the enzyme, what would happen?
The enzyme would return to its normal shape and the reaction would be reversed and would be able to continue
Example of non-competitive inhibitors causing damage
Compounds containing heavy metals such as lead, mercury, copper or silver are poisonous, as ions of these metals are non-competitive inhibitors for several enzymes - would affect enzymes in the cells, affecting metabolism in the process
Name 4 compounds containing heavy metals
Lead
Mercury
Copper
Silver
What do lead, mercury, copper and silver all have in common?
All compounds containing heavy metals, which are poisonous as their ions are non-competitive inhibitors for several enzymes
Why are some heavy metal poisonous?
Their ions are non-competitive inhibitors for several enzymes, and therefore affect certain enzymes in the cell and metabolism too
What type of inhibitors are the ions of some of the poisonous heavy metals?
Non-competitive inhibitors
Give two examples of non-competitive inhibitors
-Heavy metals (e.g - lead, mercury, copper, silver)
-Cyanide
What type of inhibitor is cyanide?
Respiratory non-competitive inhibitor
Why is it bad that cyanide is a non-competitive respiratory inhibitor?
Stops someone from being able to produce ATP = stops metabolic activity in the cell
Why would not being able to product ATP be bad?
Stops metabolic activity in the cell
What would stop metabolic activity in a cell?
Not being able to produce ATP
(Perhaps from a respiratory non-competitive inhibitor like cyanide…)
Describe the lines on a graph showing the effect of increasing substrate concentration on enzyme inhibition
Without inhibitor - steepest, reaches the maximum rate of reaction
With competitive inhibitor - less steep, but reaches the same maximum rate of reaction
With non-competitive inhibitor - least steep, doesn’t reach the maximum rate of reaction
How come that the rate of reaction without an inhibitor and with a competitive inhibitor reaches the maximum rate as the substrate concentration increases for both?
All active sites are saturated
Which two enzyme inhibition scenarios both reach the maximum rate of reaction as the substrate concentration increases and why?
Without inhibitor and with competitive inhibitor as all active sites are saturated
What happens to the rate of reaction to a competitive inhibitor as the substrate concentration increases?
Increases, but is lower than without an inhibitor as they interfere
Why does the non-competitive inhibitor have a lower rate of reaction and doesn’t reach the maximum rate of reaction as the substrate concentration increases compared to without an inhibitor and with a competitive inhibitor?
A certain proportion of enzyme molecules will be attached to a non-competitive inhibitor at a given time, decreasing the amount of available active sites for the substance - active sites are all saturated with substrate at a lower level
Which inhibitor condition has the lowest rate of reaction as the substrate concentration increases and why?
With a non-competitive inhibitor
The active sites are all saturated with substance at a lower level
Why does the rate of reaction not reach maximum with a non-competitive inhibitor as the substrate concentration increases?
As a certain proportion of enzyme molecules will be attached to a non-competitive inhibitor at a given time, decreasing the amount of available active sites for the substance
Which inhibitor condition doesn’t reach the maximum rate of reaction as the substrate concentration increases and why?
With a non-competitive inhibitor
Active sites are all saturated with a substance at a lower level
What does increasing the substrate concentration do to the affect of the competitive inhibitor and why?
Decreases its affect as the enzyme is more likely to collide with a substrate molecule and form a successful enzyme-substrate complex
What condition decreases the effect of a competitive-inhibitor and why?
Increasing the substrate concentration as the enzyme is more likely to collide with a substrate molecule and form a successful enzyme-substrate complex
How does increasing the substrate affect the rate of reaction in the case of the non-competitive inhibitor and why?
Doesn’t increase the rate of reaction as the substrate can no longer fit in the enzyme’s active site
In which case will increasing the substrate concentration to increase the rat of reaction and why?
Non-competitive inhibitors
The substrate can no longer fit into the enzyme’s active site
What does end-product inhibition occur in?
Some metabolic reactions
What’s a risk that can occur in some metabolic pathways?
The end-product may build up in the cell and reach toxic concentrations if the reaction continues
When could toxic concentrations occur in metabolic pathways?
When the end product builds up
What can happen in some metabolic pathways if the end product builds up?
Toxic concentrations may be reached in the cell
In which processes can end-product inhibition occur?
Some metabolic reactions
End-product inhibition
The molecule formed at the end of a metabolic pathway acts as a competitive inhibitor to one of the enzymes in the pathway
What’s it called when the molecule formed at the end of a metabolic pathway acts as a competitive inhibitor to one of the enzymes in the pathway?
End-product inhibition
What type of inhibitor does the end product act as in the metabolic pathway during end-product inhibition?
A competitive inhibitor
What does end-product inhibition do?
Slows down or inhibits the reactions in a metabolic pathway so that the end product doesn’t reach toxic concentrations in the cell
How does end-product inhibition ensure that conditions in a cell don’t reach toxic concentrations?
Slows down or inhibits the reaction in a metabolic pathway so that the end product doesn’t build up too much
What build up to cause toxic concentration within a cell?
The end-product of a metabolic pathway
Which process stops toxic concentrations=t ions from Ewing reached within a cell?
End-product inhibition
What must be ensured for end-product inhibition to work?
Part of the molecule must have a shape that’s complementary to the active site of the first enzyme to compete with the substrate for it
The shape of which active site must the end-product molecule be complementary to to compete with a substrate for it?
The first enzyme in the metabolic pathway
What’s significant about the first enzyme in a metabolic pathway?
The end-product molecule must have a shape that’s complementary to its active site in order to compete with a substrate molecule for it for end-product inhibition
Which industries are enzymes used in?
Food, pharmaceutical and agrochemical
What type of enzymes in particular are used on an industrial scale?
Immobilised
What are immobilised enzymes often used on?
An industrial scale
Immobilised enzymes
Enzymes that have been immobilised (fixed, bound or trapped) by being put in an inert/non-reactive support matrix
Immobilise
Fix, bound or trap
Word for fixing, bounding or trapping an enzyme
Immobilising
How are enzymes immobilised?
They’re put in an inert/non-reactive support matrix
Describe the support matrix that enzymes are put in in order to be immobilised
Inert/non-reactive
Solid or semi-solid
4 examples of immobilisation of enzymes
Adsorption
Encapsulation
Entrapment
Covalent bonding
What are Adsorption, encapsulation, entrapment and covalent bonding all examples of?
Emobilising enzymes
What does asorption immobilisation use?
Charged polar glass to attract enzymes
Which type of enzyme immobilisation uses charged polar glass?
Adsorption
What does encapsulation for the emmobilisation of enzymes require?
A permeable membrane (e.g -nylon)
Permeable membrane example
Nylon
What is nylon an example of?
A permeable membrane
Which type of enzyme emmobilisation requires a permeable membrane?
Encapsulation
How does entrapment emmobilisation of enzymes work?
Use a gel (e.g - alginate) that form long, thin polymer units, where the substrate can easily enter but the enzymes are too big to exit the matrix of the gel
How can substrates enter the matrix of an emmobilised enzyme?
Easily
Can emmobilised enzymes exit their matrix? Why?
No - they’re too big
Example of a gel used for the entrapment emmobilisation of enzymes
Alginate
Alginate
Type of gel from seaweed used for the entrapment of emmobilised enzymes in a matrix
Which type of enzyme emmobilisation uses a gel to form a matrix?
Entrapment
What does the alginate gel form during the entrapment emmobilisation of enzymes?
Long, thin polymer units
What are the long, thin polymer units of the matrix in the entrapment emmobilisation of enzymes?
Gel, such as alginate
With covalent bonding emmobilisation of enzymes, what is required?
Support (e.g - cellulose)
Which type of enzyme emmobilisation requires support?
Covalent bonding
What’s an example of a support system for covalent bonding emmobilisation of enzymes?
Cellulose
What does cellulose do in terms of emmobilised enzymes?
Supports covalent bonding emmobilised enzymes
Name a type of immobilised enzyme which has an industrial use
Alginate beads
What are the majority of the world intolerant to - what is this and why?
Lactose (milk sugar)
They don’t produce the enzyme that digests it
Why are the majority of the world lactose intolerant?
They don’t produce the enzyme that digests it
Milk sugar
Lactose
How can lactose content in milk be decreased?
Using the enzyme lactase
What can the enzyme lactase be used for?
Reducing lactose content in milk
How does lactase reduce lactose?
Breaks the disaccharide into glucose and galactose
How is the disaccharide lactose broken down into glucose and galactose?
Using the enzyme lactase
Describe the process of reducing the lactose content in milk with alginate beads
Continuous
Name a continuous process
Reducing the lactose content in milk with alginate beads
What are the alginate beads with the immobilised enzymes contained within for reducing the lactose content in milk?
A wide glass tube
What’s at the bottom of the wide glass tube that contains alginate beads for reducing the lactose content in milk?
A tap to regulate flow rate where the products come out
What happens as milk flows through the column containing immobilised enzymes?
The substrate (lactose) diffuses into the alginate matrix and forms an enzyme-substrate complex with the lactase enzyme
What’s our substrate in the case of using alginate beads to reduce the lactose content in milk?
Lactose
What does lactose act as when reducing its content in milk?
A substrate
What are the products from the formation of enzyme-substrate complexes within the alginate matrix to reduce lactose content in milk?
Monosaccharides glucose and galactose
What do glucose and galactose (our products) do after being formed from the enzyme catalysed reaction within the alginate beads?
Diffuse out of the alginate beads and leave the column with the rest of the milk
What diffuses out of the column when catalysing lactose to reduce its content in milk?
The monosaccharide products - glucose and galactose
How can more successful enzyme-substrate complexes be formed within the wide glass tube when reducing the lactose content in milk? Why?
Reduce the flow rate of the milk, allowing more contact time between enzyme and substrate, allowing more successful enzyme-substrate complexes to be formed
How can we make diffusion take place quicker within the wide glass tube for reducing lactose content in milk? Why?
Smaller beads, as this increases the surface area
How can we make diffusion take place quicker when reducing lactose content in milk?
Use smaller beads, as it increases the surface area
What would decreasing the flow rate of milk do when reducing lactose content in milk?
Allows more contact time between enzyme and substrate, allowing more successful enzyme-substrate complexes to form
Name 8 advantaged of using immobilised enzymes
- Greater control over the process
- The enzyme does not contaminate the product
- The immobilised enzymes can be recovered and reused
- They can be used in a continuous process
- Only a small quantity of enzyme is needed
- The enzymes have greater stability and denature at higher temperatures compared to enzymes free in solution
- Immobilised enzymes can catalyse reactions over a wider range of pH
- More than 1 enzyme can be used -enzymes can be added or removed
Example of immobilised enzymes not contaminating our product
Milk stays within the beads when reducing its lactose content
What does adding immobilised enzymes do to the process?
Speeds it up
What does removing immobilised enzymes do to a process?
Slows it down
How do we speed up a process involving immobilised enzymes?
Add more immobilised enzymes
How do we slow down a process involving immobilised enzymes?
Remove immobilised enzymes
Two examples of uses of immobilised enzymes
- In alginate beads to reduce lactose content in milk
- Biosensors
Biosensor
A device for measuring the concentration of a specific molecule in a mixture by converting a chemical reaction into an electrical signal
A device for measuring the concentration of a specific molecule in a mixture by converting a chemical reaction into an electrical signal
Biosensor
What do biosensors measure?
The concentration of a specific molecule
How does a biosensor measure the concentration of a specific molecule?
Converts a chemical reaction into an electrical signal
Why are immobilised enzymes used in biosensors?
Only react with their substrate (are specific)
What would a higher concentration of a substrate in a mixture do to the strength of the reaction?
The higher the concentration, the stronger the reaction
What happens within the biosensor as the concentration of a substrate increases?
Higher concentration of substrate - higher strength of electrical signal
What happens if the concentration of substrate is high within the mixture in a biosensor?
Stronger reaction —> higher signal from the electrode —> converted to a higher electrical signal
How would we get a higher electrical signal within a biosensor?
Higher signal from the electrode due to the stronger reaction from a higher concentration of the substrate in the mixture
What does a higher electrical signal within a biosensor mean?
A higher concentration of the substrate
What’s the first step within a biosensor?
Sample hits the immobilised enzymes to form enzyme-substrate complexes and form products
What happens when products are formed within a biosensor?
Detector/electrode detects the presence of H202
high concentration = higher signal from electrode
What happens within a biosensor when the electrode has generated a signal?
This is converted into an electrical signal
What happens within a biosensor when an electrical signal has been generated by the electrode?
Electrical signal to an amplifier then a computer to be put on display
What’s the unit used on a biosensor?
ppm
Example of a sample that we could measure its substrate concentration in a biosensor
Glucose
What’s the immobilised enzyme that would catalyse glucose?
Glucose oxidase
Glucose oxidase
Immobilised enzyme that catalyses glucose
What’s the product of reacting glucose oxidase with glucose?
Hydrogen peroxide
What happens to amino groups of enzymes in acidic solutions?
Gain hydrogen atoms, giving it a positive charge
When do the amino groups of an enzyme become positively charged?
When gaining hydrogen atoms in acidic solution
What happens to the carboxyl group of an enzyme in alkaline solution?
Becomes negatively charged as it loses hydrogen ions
When does the carboxyl group of an enzyme become negatively charged?
When in alkaline solution as it loses hydrogen ions
Draw and label a graph showing a reaction occurring in terms of energy
(Check notes - under catalysis)
Is the shape of the active site permanent following the substrate ‘inducing’ it its fit?
No - it’s unchanged by the reaction and can be re-used
Can induced fit enzymes be reused?
Yes
How do you calculate a rate when the dependant variable is the time?
1
——
Time
How do you calculate a rate when the dependant variable is quantity?
Quantity
————
Time
What’s the relationship between time and a rate?
The shorter the time, the higher the rate
How do we work out optimum temperature or pH?
The shortest time or the highest rate
What does the shortest time or the highest rate represent?
Optimum pH/temperature
What does 1/time calculate?
A rate
What does quantity/time calculate?
A rate
Unit of rate
s-1
Give an example of an important immobilised enzyme in a biosensor for diabetics
Glucose oxidase, to help detect glucose levels in the blood sample
Which group of people can benefit from biosensors and why?
Diabetics, as using the immobilised enzyme glucose oxidase allows them to detect the amount of glucose in their blood
what’s the difference between an inactivated and a denatured enzyme?
denatured - permanent change
inactivated - reversible
how does inactivation and denaturing of an enzyme in terms of pH vary?
inactivation - occur either side of optimum pH, charges on active site repel the substrate
denatured - more at the extremes, ionic bonds broken in the active site
Why do immobilised enzymes work at their maximum rates over a wider temperature than free enzymes?
More energy required to overcome weak bonds
Protection from higher temperatures
Shapes of active sites are maintained at higher temperatures
Which react fastest at lower temperatures - immobilised enzymes or non-immobilised enzymes? Why?
Non-immobilised
More kinetic energy and free to move
What are the key words to use in all enzyme questions?
Complementary
Specific
Enzyme-substrate complex
What do we discuss in “difference in rate” questions with a graph?
Limiting factors at different points
Why does an immobilised enzyme work at its maximum rate over a wider range of temperatures?
Stability from higher temperatures
More energy required to overcome weak bonds
Shape of active site is maintained at higher temperatures
Why must a instance used to immobilise an enzyme be inert?
Must not affect the shape of the active site by reacting with the enzyme
How does an enzyme actually catalyse a reaction?
When the substrate is in the active site, it puts strain o the bonds that are going to be broken in the substrate
Why do the products of enzyme reactions leave?
They’re no longer complementary to the active site
What do we always need to refer to when there’s an enzyme question based on temperature?
Kinetic energy
