4 Enzymes Flashcards
What is an enzyme?
A biological catalyst
Made of protein
Lowers activation energy
The active site is complementary to the substrate
How do you test for enzymes in a sample?
(Test for proteins)
Biuret’s solution
Intracellular vs extracellular
Intracellular: inside cell e.g. catalase
Extracellular: outside cell e.g. amylase
Define a catabolic reaction.
Break down
Define anabolic reaction.
Build up
State if the following are intracellular or extracellular enzymes:
a) catalase
b) trypsin
c) amylase
a) intracellular
b) extracellular
c) extracellular
State what the following enzymes catalyse the break down of and the products formed:
a) catalase
b) trypsin
c) amylase
a) hydrogen peroxide into water and oxygen
b) proteins into amino acids (hydrolysis of peptide bonds)
c) starch into maltose (hydrolysis)
Explain the lock and key hypothesis.
Substrate enters active site
Enzyme-substrate complex formed
Substrate broken down
Enzyme-products comped formed
Products leave active site
Explain the induced fit hypothesis.
Substrate enters active site
Enzymes-substrate complex is formed
Active sight slightly changes shape as substrate binds
Substrate is complementary to active site
Products leave the active site of enzyme
Explain one difference between the induced fit hypothesis and the lock and key hypothesis.
Lock and key hypothesis- the enzymes is rigid and the active site does not change shape
Induced fit hypothesis- the active site changes shape slightly as the substrate binds
How do enzymes lower activation energy?
When the substrate binds and forms an enzyme-substrate complex it strains the substrate
This distorts the bonds
And lowers the activation energy
What does it mean if an enzymes denatures?
The shape of the active site has changed
The enzyme-substrate complex cannot form
The enzyme no longer functions
Name 5 factors that have an effect on enzyme activity.
Temperature
pH
Concentration of substrate
Concentration of enzyme
Inhibitors
Name 3 ways enzyme catalytic reactions can be measured.
Measure the:
Disappearance of products
Formation of products
Rate of reaction
Describe how enzyme activity is affected as temperature increases/ at different pH’s.
Initially, the rate of reaction increases rapidly until it reaches a peak (easy enzyme-substrate contact).
After this, the rate of reaction decreases rapidly until it is finished.
Peak= optimum temperature/pH
Explain the term biological catalyst.
A substance that increases the rate of reaction
By lowering the activation energy
It speeds up metabolic reactions
Describe how substrate and enzyme concentration affects rate of reaction/ enzyme activity.
As long as the enzyme/substrate concentration is high enough, the relationship between the enzyme/substrate concentration and rate of reaction is linear.
If the enzyme/substrate concentration is not high enough then Vmax is reached (maximum rate of reaction).
What is the equation for the temperature coefficient?
Q10= rate at (t + 10 degrees)/ rate at t degrees
What bonds are affected when an enzyme denatures and which structure are these bonds in?
Hydrogen and ionic bonds
Tertiary structure
Is a denatured enzyme due to
a) temperature
b) pan
always permanent? Explain your answer.
a) yes- the specific shape of the active site is lost
b) no- if the structure is not changed significantly, renaturation can occur (original shape of active site is returned)
Explain how low temperature affects enzymes.
The number of successful collisions decreases
Because the molecules have less kinetic energy
Therefore, fewer complexes are formed
And the rate of reaction is slower
Explain how increasing the temperature affects enzymes.
The number of successful collisions increases
Because the molecules have more kinetic energy
More substrate-complexes are formed (and more products are formed)
And rate of reaction is faster
Define the term ‘inhibitor’ in relation to enzymes.
A substance that indirectly or directly interferes with the functioning of the active site of an enzyme.
Most are temporary attachments, but there are also permanent inhibitors.
Describe the differences between competitive and non-competitive inhibitors.
Competitive (C): similar shape to substrate
Non-competitive (N): doesn’t have to be like the substrate
C: can fit into active site of enzyme
N: attached to inhibitor site
C: competes with substrate
N: does not compete with substrate
C: causes a shower reaction
N: causes a change in shape of the active site so the enzyme cannot bind
C: direct
N: indirect
What is end product inhibition?
The end product of a chain of reactions inhibits the enzyme in an earlier reaction (in the chain).
What is a cofactor?
A non-protein substance
That binds to an enzyme
And is needed for the enzyme to function
What is a coenzyme?
An organic cofactor (has carbon)
What is a prosthetic group?
A cofactor
That is permanently attached to an enzyme.
How do inorganic cofactors work?
They are (often) carriers- they move chemical groups from one enzyme to another
They are changed by participating in a reaction.
What is precursor activation?
When an enzyme is activated by something to work.
How do inorganic cofactors work?
They help the enzyme and substrate bind (change the shape of the active site to make fit better).
They are not part of the reaction.
What is the cofactor for amylase?
Chlorine ion (Cl-)
What enzyme is a zinc ion a prosthetic group for?
Carbonic anhydrase
Name a source of coenzymes.
Vitamins
