2.4- Enzymes Flashcards
What are enzymes?
Biological catalyst which speed up chemical reaction.
They work both at a cellular level and for the organism as a whole
What are the two main types of enzyme action called?
Intracellular and extracellular
What are three examples of processes which involve enzymes?
Respiration
Digestion
Production of collagen
What is an example of an intracellular enzyme?
Catalase
What is the function of catalase?
It works inside cells to catalyses the breakdown of hydrogen peroxide to harmless oxygen and water
What are two examples of extracellular enzymes?
Amylase
Trypsin
What is the function of amylase?
It is found in saliva and catalyses the breakdown of starch into maltose in the mouth
What is the function of trypsin?
Trypsin catalyses the hydrolysis of peptide bonds turning big polypeptides into smaller ones
It is produced in the pancreas and secreted into the small intestine
What type of proteins are enzymes?
Globular
Ronald is labelling an image of an enzyme in action. What are three things he should label?
Active site
Substrate
Products
What is the specific shape of an active site determined by?
The enzymes tertiary structure
How do enzymes affect activation energy?
They reduce the amount of activation energy that is needed which speeds up the rate of reaction
When a substrate binds to an active site, an enzyme-substrate complex is formed. How does this lower the activation energy?
Attaching molecules close together reduces repulsion between the molecules so they can bond more easily
An active site puts a strain on bonds in the substrate so it can break up more easily
What are the two models which explain the action of enzymes?
The lock and key model
The induced fit model
What is explained in the induced fit model which is not in the lock and key model?
Why enzymes are so specific and only Bond to one particular substrate
How the active site changes shape slightly
Explain how temperature affects enzyme activity.
An increase in temperature means that molecules have more energy and the more likely to collide and create enzyme-substrate complexes
If the temperature goes above a certain level some of the bonds that hold enzyme in shape of broken and the active site changes shape. At this point the enzyme is denatured
How can we show how the rate of reaction changes with temperature?
With the temperature coefficient Q10
Q10=2 means the rate doubles when temperature is increased by 10 degrees celcius
How does pH affect enzyme activity?
All enzymes have an optimum PH value
Above and below optimum pH, hydrogen and hydroxide ions can interfere with ionic and hydrogen bonds which hold enzymes tertiary structure in place. This makes the active site change shape
How does enzyme concentration affect the rate of reaction?
The more enzyme molecules that are , the more likely a substrate is to collide with one and form an enzyme substrate complex. So increasing the concentration of the enzyme increases the rate of reaction.
However, if the amount of substrate is limited, there is a point where enzyme concentration has no further effect
How does substrate concentration affect the rate of reaction?
The high the substrate concentration the faster the reaction, as more substrate molecules means achalasia green substrate and enzyme is more likely
However, this is only true up to a certain point as once all the active sites are full, adding more substrate makes no difference to the rate of reaction
How can you measure the rate of an enzyme controlled reaction? (two-ways)
Using a gas syringe
Regular sampling of a mixture at timed intervals
What is the definition of a cofactor?
A substance which an enzyme needs to work. They help the enzyme and substrate bind together. They don’t get used up.
What is the definition of a coenzyme?
An organic cofactor is a molecule that acts as a carrier between enzymes. they are continually recycled during this process.
If a cofactor is tightly bound to an enzyme, what is it known as?
The prosthetic group
What are the two types of enzyme inhibition?
Competitive and non-competitive
What is the definition of a competitive inhibitor?
A molecule that has a similar shape to that of the substrate.
They block the active site so no substrate molecules can fit in.
What is the definition of a non-competitive inhibitor?
A molecule that binds to the enzyme or way from its active site.
This course is the active site to change shape so the substrate can no longer bind to it
What is the site that non competitive inhibitors bind to called?
Allosteric site
Shawna adds an inhibitor which has strong covalent bonds to a reaction. Why is this inhibitor irreversible?
The inhibitor can’t be removed easily
Shawna adds a reversible inhibitor to a reaction. What type of bonds must the inhibitor have?
Weaker hydrogen bonds are weak ionic bonds which can be easily
How are reverse transcriptase inhibitors a medicinal drug?
They inhibit the enzyme reverse transcriptase which catalyses the replication of viral DNA.
This prevents the virus from replicating
How do antibiotics act as a medicinal drug?
Penicillin inhibits the enzyme transpeptidase which catalyses the formation of proteins in bacterial cell walls.
This weakens the cell wall and prevents the bacterium for regulating its osmotic pressure which causes the cell to burst.
What does cyanide inhibit?
cytochrome c oxidase -An enzyme that catalyses respiration reactions
What does malonate inhibit?
succinate dehydrogenase- An enzyme which catalyses respiration reactions
What does arsenic inhibit?
pyruvate dehydrogenase- An enzyme which catalyses respiration reactions
How can protease enzyme inhibition help protect cells?
Proteases are synthesized as inactive precursors to stop them damaging proteins in the cell in which they are made
give an example of a cofactor and its enzyme
Chloride ions (Cl-) are cofactors for the enzyme amylase
give an example of a prosthetic group and its enzyme
Zn ions (Zn2+) are a prosthetic group for carbonic anhydrase (an enzyme in red blood cells which catalyses the carbonic acid from water and carbon dioxide)
