3.1.4.2 Many Proteins are Enzymes Flashcards
What do enzymes do in living cells
Control reactions
What do enzymes do
So what are they
Speed up reactions
Biological catalysts
What do enzymes not do to reactions
Cause then
2 advantages of enzymes
Can be used over + over
Effective in small amounts
What were enzymes discovered in in 1900
What type of enzyme
In yeast
Extracellular
What does the word ‘enzyme’ mean
‘In yeast’
How many different enzymes are there in human cells
40,000
What is each enzyme like to different chemical reactions
Specific
What do enzymes do to rate of reactions
Increase by up to 10(12) times
What would the speed of reactions not do without enzymes
Support life
What type of protein structure do enzymes have
Tertiary
Globular proteins
What’s an enzymes function determined by
It’s complex structure
Wheee does the reaction in an enzyme take place
In the active site
Only a few of what are involved in enzyme reactions
What type
Amino acids
Catalytic amino acids
What do catabolic reactions do
Break down
What do anabolic reactions do
Build up
What does the tertiary structure do in enzyme reactions
Brings them together
What binds in the active site
What does the rest of the protein do
The substrate
Acts as support
What do enzymes only bind with and control as they’re specific
Only bind with 1 substrate
Control only 1 reaction
What are the substrate and active site to each other
Complementary
What do enzymes ALWAYS form when they combine with their substrate
enzyme-substrate complexes
Why are enzyme-substrate complexes released as products
Due to their change in shape (after they bond)
Why can enzymes be re-used
As they aren’t altered or used up by reactions
Enzymes are energy efficient but what do they not do
What
Don’t last forever
As can be denatured/digested by protease
What do many enzymes also need to function
Other chemicals - coenzymes
What can slow down/stop enzyme function
Inhibitors
What inhibitor slows down enzyme function
Competitive
What inhibitor stops enzyme function
Permanent
Formula for enzyme function
Enzyme + substrate -> enzyme-substrate complex -> enzyme + products
How long does the enzyme-substrate complex last
Only temporarily while the substrate is sat in the active site
What are the 2 enzyme hypothesis’ s
Lock + key hypothesis
Induced fit hypothesis
What type of model is the lock + key hypothesis
What’s the active site like towards the substrate
Rigid
Active site is the inverse shape of the substrate - its complementary
How does the substrate form the enzyme-substrate complex in the lock + key hypothesis
The substrate fits into the precise shape (active site)
What does the lock+ key hypothesis not fully explain
The stabilisation of the enzyme - substrate complex
What’s the most generally accepted mechanism of action theory
Induced fit hypothesis
What is the active site not in the induced fit hypothesis
Active site is not a rigid shape
What does the active site do in the induced fit hypothesis when the substrate is attracted to it
Active site changes shape and modules around the substrate
Whats formed in the induced fit when the active site ,oilers around the substrate
What does the enzyme carry out
The enzyme-substrate complex
Enzyme carries out its catalytic function
How do the products differ in the 2 hypothesis’
In the induced fit hypothesis they have a different shape so are no longer complementary to the active site
Lock + key are ^
What do the products do at the end of the induced fit hypothesis as they’re not complementary anymore
Detach and leave the enzyme completely
What does the enzyme do at the end of the induced fit hypothesis until another enzyme arrives
Reverts back to its original state
Why does the shape of the active site change in the induced fit hypothesis
To accommodate the substrate
What happens to bonds in chemical reactions
Old bonds are broken
New bonds form
What’s the energy required to break bonds in chemical reactions
Activation energy
What does the substrate require energy from to react in any chemical reaction
Heat
What do enzymes do to the activation energy
What does this allow
Lower it
Allows reactions to take place at lower temperature
What do enzymes do to reactions as they all them to take place at lower temperatures
Make them more energy efficient
What 2 things does enzymes lowering activation energy cause to increase
Likelihood of correct reaction taking place (correct enzyme-substrate complexes form)
Rate of reaction
3 factors affecting rate of reaction
Temperature
PH
Substrate concentration
What’s the optimum temperature in humans at which enzymes work fastest
37*c
What are Molecules that may have optimum at very different temperatures called
E.g
Extremophiles
E.f bacteria in volcanoes/Arctic
What does increasing temperature do to kinetic energy
How does this increase rate of reaction
It increases kinetic energy
So are more collisions forming enzyme-substrate complexes
Increasing rate of reaction
What do collisions form
enzyme-substrate complexes
How can enzymes become denatured due to increasing temperature
Increasing temperature vibrates molecules violently
Breaks hydrogen bonds and other forces within enzyme (ionic bonds)
Altering tertiary 3D shape
So active site no longer fits substrate to form enzyme-substrate complexes
What’s the temperature for denaturing approximately in humans
60*C
What’s rate of reaction basically all about
The probability of enzyme colliding with substrate to form an enzyme-substrate complex
What’s normally the best pH for enzymes to work at
7
What pH to protease enzymes work best at in the stomach
Why
ph 1-2
Hydrochloric acid
What does PH affect at the active site
What does this affect and cause
pH affects charge of amino acids at active site
Affecting ionic bonds
So substrate can no longer bind to form enzyme-substrate complex
What can change in pH do to enzymes
Denature enzymes
Sum up denaturing
Change of charge
Unravel of shape
How does substrate concentration increase rate of reaction
As the substrate concentration increases
What’s all filled as the enzyme is working at fully capacity (large substrate concentration )
All active sites filled
How can more active sites be filled
Due to more collisions between enzyme and substrate
What isn’t all being used in low substrate concentrations
Not all enzyme molecules are being used
More of what is formed as substrate concentration increases
More enzyme-substrate complexes
What does not affect rate when all active sites are in use (saturated)
Substrate concentration
What is the part of a graph called that isn’t stopped but is just at a steady state
Plateau
What can inhibitors do to enzymes catalytic activity
Slow it down or stop it
What type of process is inhibitions
What’s it for
Natural
To switch enzymes on/off when needed
What is inhibition mostly
What’s exceptions
E.g
Reversible
But some poisons are permanently inhibiting e.g heavy metal like mercury
What happens to the enzyme when the inhibitor is removed if it’s reversible
Returns to Normal
2 types of reversible inhibitors
Competitive
Non-competitive
What do competitive inhibitors do and why
Compete with substrate molecules to occupy the active site
What can competitive inhibitors not be converted to even though they have similar structure to substrate
Products
What do competitive inhibitors reduce
Number of enzyme-substrate complexes being formed
What do competitive inhibitors do to the final amount of product formed
Nothing it’s the same
But just takes longer
What happens to rate if there’s an equal amount of substrate and competitive inhibitors
Rate is halved
What reduces the effect of competitive inhibitor
Increase in substrate concentration
What does the competitor not cause
Damage
Where do non-competitive inhibitors bind to the enzyme
Away from the active site (allosteric site)
What topic do we see non-compatible inhibitors in
Homeostasis
What do non competitive inhibitors change
The overall shape of the molecules including the active site indirectly
What’s there no competition for with non-competitive inhibitors
The active site
What molecules do non-competitive inhibitors reduce the amount of
Active enzyme molecules (more are inactive)
What do non-competitive inhibitors do to rate of reaction
How
Decrease it by decreasing number of enzyme-substrate complexes
What doesn’t reduce the affect of non-competitive inhibitors
Increase if substrate concentration
How do non-competitive inhibitors change active site shape
Pull out of shape
