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Compare the Role of Enzymes in the Digestive System

In this worksheet, students will compare the role of enzymes in the digestive system.

Worksheet Overview

QUESTION 1 of 10

Did you know that our saliva contains something called enzymes? And did you know that without these enzymes digestion wouldn't be able to occur? So what are these enzymes anyway and how do we use them in digestion?

Enzymes are proteins. They are biological catalysts that speed up a chemical reaction without being used up in the reaction. Enzymes have a complex 3D shape. The specific shape that allows molecules to fit in is called the active site. It's here that large insoluble food substances are broken into smaller soluble molecules. Smaller molecules are easily absorbed by the blood. These smaller molecules might be used for different processes, for example, glucose can be used for respiration. Some smaller molecules will be used to build and make new products. Proteins can be broken down into peptides which are short chains of amino acids and then further broken down into amino acids. These amino acids can be used to build new proteins needed for growth and repair.

The lock and key theory 

The shape of the active site of an enzyme matches the shape of the food molecule (substrate), a bit like a key is specific to the lock it opens, a substrate will only match a specific enzyme. This is called the lock and key theory

Image showing enzyme in action

Different types of food are broken down by different enzymes.  Digestive enzymes are classified by the type of food that they affect; there are three main types:

  • carbohydrase – breaks carbohydrate into smaller sugars
  • protease – breaks protein into amino acids
  • lipase – breaks fat into fatty acids and glycerol

Carbohydrates

Carbohydrates are chains of identical sugar molecules. The digestive enzyme called carbohydrase breaks the chemical bonds between the sugar molecules in each carbohydrate chain. An example is amylase. Amylase is found in saliva and pancreatic juices. Amylase breaks starch down into small sugar molecules called maltose. Maltose can be further converted to glucose by another enzyme called maltase in the small intestine.

Image of starch broken into maltose by amylase enzyme

Proteins 

Proteins are made up of amino acids. There are over 20 different types of amino acids. Proteins are digested by digestive enzymes called proteases. These enzymes break proteins into smaller peptides and individual amino acids. Amino acids can be built up to make new proteins for growth and repair. Proteases can be found in the stomach, pancreas and small intestine.

Image of protein into amino acid by protease enzyme

Fats

Fats are digested in two stages:

Firstly, bile (made by the liver) emulsifies fat into smaller droplets called an emulsion. This increases the surface area of the fat. 

Secondly, the digestive enzyme lipase breaks each fat molecule into the smaller glycerol and fatty acid molecules. These can now be absorbed by the blood and can be used by the body for energy storage and building cell structures like cell membranes. Bile is alkaline and helps to neutralise the acidic food leaving the stomach.

Lipases are found in the pancreas and small intestine.

Image of fats being broken down by bile and enzyme lipase 

In the following activity, you will compare the different enzymes in the digestive system. 

Enzymes are super important and without them digestion can't occur. Fill in the blanks below to describe what enzymes are. 

Enzymes are very specific. They have active sites that only bind with specific food molecules, also known as substrates.

Compare the different types of digestive enzymes by matching them with their substrates.

Column A

Column B

Carbohydrase
Breaks fat into fatty acids and glycerol
Protease
Breaks carbohydrate into smaller sugars
Lipase
Breaks protein into amino acids

Below are three different images of enzymes and their substrates. Which of the three images below shows a substance in acidic conditions. Select one answer below.

A B C
 Image of starch broken into maltose by amylase enzyme Image of protein into amino acid by protease enzyme Image of fats being broken down by bile and enzyme lipase

 

A

B

C

Enzymes break down larger insoluble food molecules to smaller soluble food molecules. Starch is a carbohydrate that will often get broken down into glucose. What is the glucose used for? Type one answer below.

 

Digestive enzymes are essential for digestion to occur. Where are the main enzymes found and what do they digest? Answer this question by selecting one answer in each row.

The picture below shows an enzyme and three substrate molecules. 

Image of enzyme and three different substrates

Which substrate will react with the enzyme? Type one answer. 

Proteases are enzymes that catalyse proteins.

Image of protein broken down into peptides and amino acids

Label A. Select one answer

Amino acids

Peptides

Glucose

Image of food groups

Carbohydrates, proteins and lipids are major nutrients. These are needed by the body and we get these nutrients by eating them. 

What do these nutrients provide? Match up the nutrient with its function.

Column A

Column B

Carbohydrates
Growth and repair
Proteins
Source of energy
Lipids
Energy, essential part of cell membranes

All digestive enzymes have some similarities. Select three similarities below. 

Catalyse lipids

Biological catalysts

Catalyse proteins

Catalyse specific substrates

Have specific active sites

Bile and lipase both play an important role in the digestion of fats. Compare bile and lipase by filling in the blanks below.

 

Catalyse lipids

Biological catalysts

Catalyse proteins

Catalyse specific substrates

Have specific active sites

The table below shows a summary of the digestive enzymes and their specific functions. Match up A, B and C.

Carbohydrase Protease
A  Proteins → Amino acids  Lipids → Glycerol + Fatty acids
 Energy, respiration B  Energy, Cell membranes
Salivary glands, Pancreas, Small intestine Stomach, Pancreas, Small intestine Pancreas, Small intestine

 

Column A

Column B

A
Lipase
B
Carbohydrates → Sugars
C
Growth and repair
  • Question 1

Enzymes are super important and without them digestion can't occur. Fill in the blanks below to describe what enzymes are. 

CORRECT ANSWER
EDDIE SAYS
A common misconception is that enzymes get used up in reactions. Enzymes help to speed up reactions but don\\\'t take part in the actual reaction so don\\\'t get used up.
  • Question 2

Enzymes are very specific. They have active sites that only bind with specific food molecules, also known as substrates.

Compare the different types of digestive enzymes by matching them with their substrates.

CORRECT ANSWER

Column A

Column B

Carbohydrase
Breaks carbohydrate into smaller ...
Protease
Breaks protein into amino acids
Lipase
Breaks fat into fatty acids and g...
EDDIE SAYS
To help you remember the name of these enzymes and their substrates, remember the clue is in the name: Carbohydrase → Carbohydrates Protease → Proteins Lipase → Lipids (another name for fats)
  • Question 3

Below are three different images of enzymes and their substrates. Which of the three images below shows a substance in acidic conditions. Select one answer below.

A B C
 Image of starch broken into maltose by amylase enzyme Image of protein into amino acid by protease enzyme Image of fats being broken down by bile and enzyme lipase

 

CORRECT ANSWER
C
EDDIE SAYS
Bile is alkaline and is added to food leaving the acidic conditions of the stomach, neutralising it.
  • Question 4

Enzymes break down larger insoluble food molecules to smaller soluble food molecules. Starch is a carbohydrate that will often get broken down into glucose. What is the glucose used for? Type one answer below.

 

CORRECT ANSWER
respiration
EDDIE SAYS
Digestion allows smaller molecules to be used by the body for important processes. Often these smaller glucose molecules will be used to build new carbohydrates.
  • Question 5

Digestive enzymes are essential for digestion to occur. Where are the main enzymes found and what do they digest? Answer this question by selecting one answer in each row.

CORRECT ANSWER
EDDIE SAYS
This activity is a great summary for revision purposes. Try this question a few times to consolidate your knowledge.
  • Question 6

The picture below shows an enzyme and three substrate molecules. 

Image of enzyme and three different substrates

Which substrate will react with the enzyme? Type one answer. 

CORRECT ANSWER
c
EDDIE SAYS
Active sites have a specific shape that is complementary to a particular substrate. Like a puzzle piece, the substrate and the active site has to be complementary or the substrate won't be broken down. C is the only substrate that has a complementary shape to the enzymes active site.
  • Question 7

Proteases are enzymes that catalyse proteins.

Image of protein broken down into peptides and amino acids

Label A. Select one answer

CORRECT ANSWER
Peptides
EDDIE SAYS
Peptides are short chains of amino acids. Amino acids are the individual compounds that can make up proteins.
  • Question 8

Image of food groups

Carbohydrates, proteins and lipids are major nutrients. These are needed by the body and we get these nutrients by eating them. 

What do these nutrients provide? Match up the nutrient with its function.

CORRECT ANSWER

Column A

Column B

Carbohydrates
Source of energy
Proteins
Growth and repair
Lipids
Energy, essential part of cell me...
EDDIE SAYS
Having a varied and balanced diet is important, it means the body will get a mixture of nutrients. The body will reassemble these nutrients depending on what the body needs.
  • Question 9

All digestive enzymes have some similarities. Select three similarities below. 

CORRECT ANSWER
Biological catalysts
Catalyse specific substrates
Have specific active sites
EDDIE SAYS
Enzymes are highly specific catalysts. The active sites have a specific shape for specific substrates.
  • Question 10

Bile and lipase both play an important role in the digestion of fats. Compare bile and lipase by filling in the blanks below.

 

CORRECT ANSWER
EDDIE SAYS
When making comparisons in longer answers in your exams, remember to use your comparative words: however conversely whereas similarly in contrast
  • Question 11

The table below shows a summary of the digestive enzymes and their specific functions. Match up A, B and C.

Carbohydrase Protease
A  Proteins → Amino acids  Lipids → Glycerol + Fatty acids
 Energy, respiration B  Energy, Cell membranes
Salivary glands, Pancreas, Small intestine Stomach, Pancreas, Small intestine Pancreas, Small intestine

 

CORRECT ANSWER

Column A

Column B

A
Carbohydrates → Sugars
B
Growth and repair
C
Lipase
EDDIE SAYS
All three enzymes are specific to the nutrient they catalyse. One main similarity you can spot in the table is that they are found in the pancreas (as well as other locations).
---- OR ----

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