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Understand The Role of Enzymes

In this activity, students will learn the function and production of enzymes, as well as the different conditions necessary for optimal enzyme action.

'Understand The Role of Enzymes' worksheet

Key stage:  KS 4

Curriculum topic:  

Curriculum subtopic:  

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Without enzymes, we wouldn’t work!

 

Every action our bodies need like breathing and eating all depend on fast reactions controlled by enzymes.

 

Both chemistry and biology are mad about enzymes, so let’s get going!

1. Question: Who are they?

Answer: Well, enzymes are a type of protein made by cells.


Reminder: A protein is a polymer of amino acids arranged in a chain and then folded.


The folding is held in place by chemical bonds, giving a unique 3D shape.

 

For enzymes, the final structure always includes an area called an active site, and this shape always only matches one molecule!

 

So NO FIT = NO REACTION!

 

 

2. Question: What do they do?

Answer: They are catalysts!


A catalyst speeds up reactions WITHOUT BEING USED UP

 

3. Question: How do they work?

Answer: THE LOCK AND KEY HYPOTHESIS:

 

 

a. The right enzyme is present, with its active site being the right fit for the starting ingredient or substrate.


b. The substrate attaches to the active site, and this perfect match is described as the enzyme-substrate complex


c. The speed of the reaction increases and a product is made, and the enzyme is reused

 

What an enzyme needs to work

 

Every enzyme has its own ideal temperature and pH!

Start with temperature, too much heat can break the bonds holding the active site together, the enzyme stops working and the reaction stops.

 

When the active site loses its shape and a substrate can’t fit in it anymore, we call this denaturation (not enzyme death because they are not living things!)

 

Changing the temperature will also change how much energy the enzyme and the substrate have to move around, and the lower the temperature, the less movement, the less chance these things have of colliding with each other and successfully making a complex, and so the reaction slows down.

 

So temperature is a fine balance!

 

 

And let's not forget pH!

 

This can also have a big impact on the active site shape, again because of the sensitivity of the bonds between the amino acids in the folded 3D structure.

 

If the pH makes a huge change outside the enzyme’s comfort zone, the active site will be denatured (break down), the substrate won’t be able to fit, which, you guessed it, slows the reaction right down!

An enzyme has the role of a catalyst, but it's actually a what?

 

Protein

Carbohydrate

Lipid

As a protein, an enzyme is made of what subunit?

Protein

Carbohydrate

Lipid

Chemical bonds in a protein hold together what?

The enzyme and substrate in the enzyme-substrate complex

The 3D shape of the active site

The product to the enzyme at the end of the reaction

Why is it important that an active site is unique?

So the body has a better control over the number of reactions being catalysed

The body doesn't have the ability to make one catalyst that can cover all chemical reactions

So other cells can't steal each other's enzymes and one is left deficent

A catalyst speeds up a reaction. 

What else is an important factor of a catalyst?

There are many different terms to describe the components of enzyme activity:

Column A

Column B

Enzyme-Substrate Complex
When a substance fits exactly into the active site...
Denaturation
When so many chemical bonds are broken that the ca...
Substrate
A reactant or starting ingredient

Label this diagram about the 'Lock and Key Hypothesis:

 

Column A

Column B

Enzyme-Substrate Complex
When a substance fits exactly into the active site...
Denaturation
When so many chemical bonds are broken that the ca...
Substrate
A reactant or starting ingredient

What is the theory about how the substrate fits into the active site called?

What two things have to be taken into account when selecting an enzyme?

 

[Select 2 options below]

Its preferred temperature

Its preferred speed

Its preferred time of day

Its preferred pH

Here is a scenario:

 

'In the stomach, Lipase works best as a catalyst in 37 degrees at pH 2 to break down fats.'

 

Indicate whether the rate of reaction would increase or decrease if the following changes were made:

  • Question 1

An enzyme has the role of a catalyst, but it's actually a what?

 

CORRECT ANSWER
Protein
EDDIE SAYS
How did you get on with this definition? An enzyme is a protein, which can also be called a polypeptide. It has a large molecule structure because it's made of many small units put together.
  • Question 2

As a protein, an enzyme is made of what subunit?

CORRECT ANSWER
EDDIE SAYS
So like we've said, an enzyme is a protein, which is a chain of amino acids that has been folded into a 3D shape. This gives then a 3D area called an active site, allowing the enzyme to perform its function as a catalyst.
  • Question 3

Chemical bonds in a protein hold together what?

CORRECT ANSWER
The 3D shape of the active site
EDDIE SAYS
So let's start with the wrong answers: The enzyme and substrate aren't actually bonded together in the complex, they just fit together, and as the enzyme needs to be reused in its role as a catalyst, the product leaves so the active site is free for another substrate to enter. The middle option is right because: Once the protein has folded into the shape it needs for its function, something has to hold everything together, and the amino acids create more links called chemical bonds so the protein can remain 3D rather than a simple one-tier chain. SO now we can reveal that denaturation is specifically the break down of the active site's unique shape as the chemical bonds holding the 3D shape break down, making the reaction slow down as the catalyst stops working.
  • Question 4

Why is it important that an active site is unique?

CORRECT ANSWER
So the body has a better control over the number of reactions being catalysed
EDDIE SAYS
Every protein is a unique sequence of many possible amino acids. This specific selection means the folding the chain does is one of a kind, meaning the active site is a space for only one substance that also has the same shape so an enzyme-substrate complex can be made with that perfect fit. This type of control means every reaction needs one enzyme and the body gets to decide if it will make this enzyme and so if the reaction will take place. If there was one enzyme that worked for all reactions, the body would start working in too many individual directions, with no organisation or synchronisation- just imagine what your heartbeat or breathing would be like!
  • Question 5

A catalyst speeds up a reaction. 

What else is an important factor of a catalyst?

CORRECT ANSWER
IT'S NOT USED UP
IT'S REUSED
IT'S RECYCLED
EDDIE SAYS
How was it answering this question? A true catalyst doesn't need to be replaced frequently and should be considered recyclable, so once one reaction is finished, while the ingredients get topped up, the catalyst can be left alone.
  • Question 6

There are many different terms to describe the components of enzyme activity:

CORRECT ANSWER

Column A

Column B

Enzyme-Substrate Complex
When a substance fits exactly int...
Denaturation
When so many chemical bonds are b...
Substrate
A reactant or starting ingredient
EDDIE SAYS
These are important new terms to understand so I hope the matches seemed straight forward. An enzyme-substrate complex is a fancy phrase for when the active site gets filled with the substance that matches its unique space- this if often the reactant in a reaction, but as it depends on the reaction, we called this varying molecule a substrate. Denaturation is the break down of the enzyme because the conditions of the reaction have damaged the chemical bonds- please note that enzymes can't die, only stop working, as they are not living things! Keep working through the questions to find out more about what we have to control in reactions to prevent an enzyme from becoming denatured!
  • Question 7

Label this diagram about the 'Lock and Key Hypothesis:

 

CORRECT ANSWER
EDDIE SAYS
So the Lock and Key Hypothesis is quite simple: Unique active site, or LOCK, is chosen for the reaction, this connects to a specific KEY making a complex, and the desired product or effect takes place, the reaction happening at a good pace and the catalyst goes on the be reused. If this concept is still a little confusing, refer back to the diagram and notes in the introduction for some help!
  • Question 8

What is the theory about how the substrate fits into the active site called?

CORRECT ANSWER
THE LOCK AND KEY HYPOTHESIS
LOCK AND KEY
EDDIE SAYS
The lock and key hypothesis refers to the unique shape of the active site and the perfect fit when an enzyme-substrate complex is made. Look at the next question for more on this concept!
  • Question 9

What two things have to be taken into account when selecting an enzyme?

 

[Select 2 options below]

CORRECT ANSWER
Its preferred temperature
Its preferred pH
EDDIE SAYS
The 2 major factors involving optimal enzyme function is TEMPERATURE and pH!!! Every enzyme has an ideal temperature range and pH to work in, and if these stray too far outside the enzyme\'s comfort zone, we get denaturation!
  • Question 10

Here is a scenario:

 

'In the stomach, Lipase works best as a catalyst in 37 degrees at pH 2 to break down fats.'

 

Indicate whether the rate of reaction would increase or decrease if the following changes were made:

CORRECT ANSWER
EDDIE SAYS
Basically, enzymes are so picky that if you start messing around and try to boost the rate of reaction, you'll probably damage the enzyme's active site! Increasing the temperature to increased the rate of reaction is understandable, as you're trying to give all the particles more energy to collide, but go too far and the enzyme denatures, slowing down the reaction instead. The same goes for pH changes, as too acidic or alkalotic and the chemical bonds start breaking and we lose the active site. If the temperature dips too low, there will be less successful collision making enzyme-substrate complexes as the reactants will have too little energy to move, which slows down the reaction, so don't be too cautious! However, a good way to increase the rate of reaction is to of course add more ingredients, and adding more enzymes and substrates will make the reaction continue for longer and so make more product. You add more substrate because it's being converted into a product, but you also need more enzyme because otherwise all the active sites will be full and won't be able to interact with the extra substrate!
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