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Understand Enzyme Function

Worksheet Overview

QUESTION 1 of 10

Your body needs chemical reactions to be able to work effectively. They are happening all the time performing functions such as digestion, respiration (so you have energy), sending signals and creating new cell parts. Everything that your body does, it achieves through chemical reactions.

But these chemical reactions would not work if it weren’t for the enzymes in your body that speed up these reactions. We’re going to be looking at what enzymes are and how they work in this activity.

 

Enzymes are biological catalysts which means they speed up reactions in the body. Enzymes are made in such a way that reacting molecules can fit into them. If you look at the image below, you can see the substrate (the thing that needs to react) fits perfectly into the active site (the part of the enzyme that does the reactions). We call this the lock and key model because the enzyme fits in the substrate like a lock and key. 

Enzymes can break down substrates, as in the image below (this typically happens in digestion and respiration) or they can put two substrates together (this will happen in plants when making glucose in photosynthesis). But it is important to remember that one enzyme has one function and that is it. It cannot do anything but its own job. There are about five different proteins needed just to do respiration. 

 

An image of a shape fitting into another shape. The two shapes fit perfectly, and then one of the shapes is broken.

 

Enzymes are 'denatured' (they no longer work) in conditions of extreme temperatures and pH. This means that you need enzymes to be specific to their environment – for example, the enzymes in your stomach are suited to work in a pH of about 1 because your stomach is acidic. If you put them into a different pH, they will become denatured (they won’t work).

They do this because their active site will change shape when moved to a different pH or temperature than they are used to. Because the active site has changed shape, the substrate will no longer fit and the enzyme won’t be able to do its job anymore. Just so you know, enzymes do not die -  they were never alive in the first place, so they can’t die. They only denature.

 

Enzymes also aid food digestion by breaking down food molecules. Amylase is found in saliva and breaks down starch into sugars. Starch is a carbohydrate and every enzyme that breaks down carbohydrates is a carbohydraseProteases break down proteins into amino acids, and lipases break down lipids (fats) into fatty acids and glycerol.

 

Are you ready to try some questions on this topic now?

What is the job of an enzyme? 

To stop reactions in the body

To make reactions happen quicker in the human body

To cause digestion

What happens to an enzyme when the active area changes shape?

It dies

It becomes denatured

It changes its function

It continues to perform its role

If you took an enzyme from the human body and put it into a cup, what temperature would you need that cup to be so that the enzyme could perform its role effectively?

20

37

49

80

How would you describe enzymes in terms of their chemical action?

Reactants

Catalysts

Triggers

What is the name of the molecules that enzymes help to react?

Active

Substrate

Monomer

What is the site on the enzyme where substrate molecules fit into?

Deactive site

Active site

Key site

What enzyme breaks down starch?

Protease

Lipase

Amylase

What is the name of the enzymes that break down fats?

Protease

Lipase

Amylase

The environment in the stomach is very acidic (pH 1). Study the diagram below and then choose a statement that describes stomach enzymes.

 

Chart to show optimum ph in the stomach

The optimum pH for enzymes in the stomach is 7

The optimum pH for enzymes in the stomach is 12

The optimum pH for enzymes in the stomach is 1

This diagram shows how enzyme activity changes according to the temperature:

 

Graph to show enzyme changes related to temperature.

 

The optimum temperature for enzymes is 37°C, because this is the normal body temperature.

 

 What happens when the temperature increases above 37°C?

Enzyme activity falls rapidly as heat denatures the enzyme

Enzyme activity decreases gradually

Enzyme activity continues as normal

  • Question 1

What is the job of an enzyme? 

CORRECT ANSWER
To make reactions happen quicker in the human body
EDDIE SAYS
Did you choose option three in error here? It was easily done! While enzymes do play a role in digestion, they work all over the body to speed up chemical reactions. We call this catalysing the reactions - because we're scientists and we like posh complicated words.
  • Question 2

What happens to an enzyme when the active area changes shape?

CORRECT ANSWER
It becomes denatured
EDDIE SAYS
Remember - enzymes can't die because they were never alive. We say they denature because their nature is not working.
  • Question 3

If you took an enzyme from the human body and put it into a cup, what temperature would you need that cup to be so that the enzyme could perform its role effectively?

CORRECT ANSWER
37
EDDIE SAYS
Enzymes only work effectively at one temperature - if it has come from a human, then it will need that temperature to be body temperature - or 37oC. If the temperature is too high, it will denature, and if it's too low, then it will not work as well as it should.
  • Question 4

How would you describe enzymes in terms of their chemical action?

CORRECT ANSWER
Catalysts
EDDIE SAYS
A hard one to finish with, wasn't it? Enzymes are catalysts that work inside living organisms - they are biological catalysts. This means that they speed up chemical reactions within the body. You've completed this activity - and it was a tricky one - so well done for getting to the end! If you are still unsure of some of this stuff, it would be a good idea to reread the Introduction and maybe have another go at the questions to see if you can improve your score.
  • Question 5

What is the name of the molecules that enzymes help to react?

CORRECT ANSWER
Substrate
EDDIE SAYS
Some really tricky sounding names here - if you found it a bit confusing, you can always go back to the Introduction and have another read through to help you sort things out in your head. Substrate molecules fit into the enzyme's active site ( a bit like pieces in a jigsaw puzzle) and the enzymes then help them to react more quickly.
  • Question 6

What is the site on the enzyme where substrate molecules fit into?

CORRECT ANSWER
Active site
EDDIE SAYS
Wouldn't be great if it were called the key site, since it is like a key! But it isn't, so you've got to learn another term. Substrate molecules fit into the active site. This mechanism is called the key-lock.
  • Question 7

What enzyme breaks down starch?

CORRECT ANSWER
Amylase
EDDIE SAYS
There's no easy way of getting these questions on enzymes right - you've just got to learn them! Amylase is found in saliva and breaks down starch into sugars.
  • Question 8

What is the name of the enzymes that break down fats?

CORRECT ANSWER
Lipase
EDDIE SAYS
Once again, there are no short cuts here - you've just got to learn these! Lipase breaks down fats (lipids) into fatty acids and glycerol.
  • Question 9

The environment in the stomach is very acidic (pH 1). Study the diagram below and then choose a statement that describes stomach enzymes.

 

Chart to show optimum ph in the stomach

CORRECT ANSWER
The optimum pH for enzymes in the stomach is 1
EDDIE SAYS
The optimum pH for enzymes in the stomach is 1. You can see this in the diagram as once the pH has reached the optimum, the rate of activity rapidly decreases again as the enzymes denature.
  • Question 10

This diagram shows how enzyme activity changes according to the temperature:

 

Graph to show enzyme changes related to temperature.

 

The optimum temperature for enzymes is 37°C, because this is the normal body temperature.

 

 What happens when the temperature increases above 37°C?

CORRECT ANSWER
Enzyme activity falls rapidly as heat denatures the enzyme
EDDIE SAYS
Could you see the dramatic drop in activity on the graph? This is because enzyme activity falls rapidly as heat denatures the enzyme. The heat will change the shape of the active area meaning that it will not be able to do its job any more.
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