2.4 Enzymes Flashcards
What is an active site?
Area on the surface of an enzyme molecule with a shape that is complementary to that of the substrate molecule.
What does metabolic mean?
Chemical reactions that take place in living organisms
What is a substrate?
A molecule that is altered by an enzyme-catalysed reaction.
What is an enzyme?
Biological catalyst that speeds up the rate of a metabolic reaction
What is the turnover number of an enzyme?
The number of reactions an enzyme molecule can catalyse per second
What is the function of catalase?
Hydrogen peroxide broken down into water and oxygen
What is the function of amylase?
In saliva, breaks down starch into maltose
What is the function of trypsin?
Catalyses hydrolysis of peptide bonds
Where is trypsin made and secreted to?
Made in pancreas, secreted to small intestine
Enzymes reduce the amount of ________ needed for a reaction to occur.
Activation energy
What is formed when an enzyme binds to a substrate?
Enzyme/substrate complex
How does an enzyme help 2 substrate molecules join?
The enzyme holds them close together, reducing any repulsion so they can bond easier.
How does an enzyme catalyse a breakdown reaction?
Fitting the molecule into the active site strains the bonds, allowing it to break up more easily.
What is the induced fit model?
As the substrate binds, the active site changes shape slightly to fit the substrate more easily.
What is the lock and key model?
The enzyme and substrate fit together like a lock and key.
What is the temperature coefficient (Q10) ?
This shows how much the rate of a reaction changes when the temperature is increased by 10 degrees
What does a Q10 value of 2 mean?
If you increase the temperature of an enzyme controlled reaction by 10 degrees the rate of reaction doubles.
What is an example of an intracellular enzyme function?
Catalase catalysing breakdown of hydrogen peroxide
What is an example of an extracellular enzyme function?
Trypsin catalysing breakdown of proteins
How does increasing temperature affect enzyme activity?
It increases enzyme activity and reaction rate until the molecules vibrate too much and and the tertiary structure bonds break, denaturing the enzyme by changing the active site shape
How does pH affect enzyme activity?
The enzyme is most active at its optimum pH, and above and below it the excess H+ or OH- interfere with ionic and hydrogen bonds within the tertiary structure, so can denature the enzyme.
How does enzyme concentration affect rate of reaction?
As you increase the enzyme concentration the rate of reaction increases until the substrate concentration becomes limiting. This is because the more enzyme molecules there are, there is more possibility of collision to form an enzyme substrate complex
How does substrate concentration affect rate of reaction?
Higher substrate concentration means a higher rate of reaction because of an increased chance of collision between substrate and enzyme, but only until the saturation point where the rate is limited by enzyme concentration
What is the saturation point?
Where there are so many substrate molecules that all the enzyme active sites are full and adding more substrate makes no difference to rate of reaction
What are cofactors?
A chemical that must be present for an enzyme to function, can be permanently or temporarily bonded.
What is a coenzyme?
Organic, non-protein molecule that binds temporarily to the active site of an enzyme to aid its function
How does a coenzyme work?
They participate in the reaction and are changed by it. They act as carriers moving chemicals between enzymes.
How do cofactors work?
They are inorganic molecules that help the enzyme and substrate bind together, and don’t participate or get used up in the reaction.
What is the cofactor for amylase?
Chloride ion, Cl-
What is the prosthetic group for carbonic anhydrase?
Zinc ion, Zn2+
What is a source of coenzymes?
Vitamins
What is a prosthetic group?
A non-protein component that forms a permanent part of a functioning enzyme
What does carbonic anhydrase catalyse?
The production of carbonic acid from water and carbon dioxide.
What is an enzyme inhibiter?
A molecule that binds to an enzyme to inhibit its action
What is a competitive enzyme inhibter?
They have a similar shape to the active site of the enzyme they are inhibiting, and block the active site from substrate molecules
What is a non-competitive enzyme inhibiter?
They bind to the enzymes allosteric site, changing the shape of the active site so substrates can no longer bind.
What is a reversible inhibitor?
The bonds are weaker (ionic, hydrogen) and the inhibitor can be removed
What is a non-reversible inhibitor?
The bonds are stronger (covalent) and the inhibitor can’t be removed
What is end product inhibition?
When the final product in a metabolic pathway inhibits an enzyme that acts earlier in the pathway
Why is end product inhibition useful?
Its an efficient way of regulating the pathway and the amount of end product made, while also being reversible.
What is end product inhibition an example of?
Negative feedback
What are metabolic poisons?
They interfere with metabolic reactions causing damage, and are often enzyme inhibitors
How do antiviral drugs work?
They inhibit the enzyme that catalyses replication of viral DNA, preventing the virus from reproducing
How do antibiotics work?
They inhibit the enzyme that catalyses formation of proteins in bacterial cell walls, which weakens the cell wall making the bacterium burst and die
What are some examples of metabolic poisons?
Cyanide, malonate, and arsenic
