2.4- Enzymes Flashcards Preview

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Flashcards in 2.4- Enzymes Deck (38)
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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?

Production of collagen


What is an example of an intracellular enzyme?



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?



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?



Ronald is labelling an image of an enzyme in action. What are three things he should label?

Active site


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