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Describe the Enzymes in the Digestive System

In this worksheet, students will describe 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 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 specific shape that allows molecules to fit into 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 amino acids, which can be reassembled into new proteins.

 

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, and breaks starch down into small sugar molecules called maltose

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 amino acids and are 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) allows the fat to ‘mix’ with water by breaking the fat into smaller droplets (emulsion). 

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. 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 describe the different enzymes that make up the digestive system.

 

 

Enzymes are super important and without them digestion can't occur.

 

Fill in the blanks below to describe what enzymes are.

Image showing enzyme in action

Enzymes break up larger food molecules into smaller food molecules. The lock and key theory is a model that describes how enzymes work.

 

Describe the lock and key theory by matching up the sentences below.

Column A

Column B

Enzymes have active sites that...
...have specific shapes
The active site shape...
matches the shape of specific food molecules
The fit between the enzyme and substrate is like.....
a lock and key
The enzyme catalyses the...
breakdown of the food molecule

Enzymes help to break up food molecules, also known as the substrates. Match up the types of enzymes with their substrates.

Column A

Column B

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

Enzymes are made in various locations around the body. Decide where each enzyme is produced.

 

Select one answer in each row.

The liver makes a substance called bile. What is the function of bile?

 

Select two answers below.

Image of the liver

Bile is an enzyme

Bile is alkaline to neutralise hydrochloric acid from the stomach

Breaks up fat to form smaller droplets

Bile is acidic and destroys microbes

Starch is a carbohydrate. In the image below, starch is broken down by the enzyme - (a) into (b).

 

What is (a) and (b)? Select two answers below.

Image showing starch being broken down into maltose

(a) Lipase

(a) Amylase

(b) Glucose

(b) Maltose

Other than the pancreas (not labelled in this picture), which part of the digestive system are proteases found in? 

 

Type two letters from the picture below.

Image of the digestive system

 

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 might we need glucose for? Select one answer below.

 

To make enzymes

Photosynthesis

Respiration

Image of protein into amino acid by protease enzyme

Certain enzymes break up proteins in our food into amino acids. The amino acids will be reassembled into new proteins needed for growth and repair.

 

Which type of enzyme breaks up proteins into amino acids? Select one answer below.

Protease

Carbohydrase

Lipase

 Are the following statements true or false? Select one answer in each row.

  • 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

Image showing enzyme in action

Enzymes break up larger food molecules into smaller food molecules. The lock and key theory is a model that describes how enzymes work.

 

Describe the lock and key theory by matching up the sentences below.

CORRECT ANSWER

Column A

Column B

Enzymes have active sites that...
...have specific shapes
The active site shape...
matches the shape of specific foo...
The fit between the enzyme and su...
a lock and key
The enzyme catalyses the...
breakdown of the food molecule
EDDIE SAYS
Enzymes and the specific food molecules they help to break down, fit together a little like a puzzle piece or a lock and key.
  • Question 3

Enzymes help to break up food molecules, also known as the substrates. Match up the types of enzymes 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 4

Enzymes are made in various locations around the body. Decide where each enzyme is produced.

 

Select one answer in each row.

CORRECT ANSWER
EDDIE SAYS
How did you do? If you notice, all the digestive enzymes mentioned above are produced in the pancreas and small intestine. It's only carbohydrases that are also produced in the mouth and proteases that are also produced in the stomach.
  • Question 5

The liver makes a substance called bile. What is the function of bile?

 

Select two answers below.

Image of the liver

CORRECT ANSWER
Bile is alkaline to neutralise hydrochloric acid from the stomach
Breaks up fat to form smaller droplets
EDDIE SAYS
A common misconception is that bile is an enzyme. Bile does help to breakdown fats through emulsification (the 'mixing' of fats with water), forming smaller droplets, which enzymes then can break down further.
  • Question 6

Starch is a carbohydrate. In the image below, starch is broken down by the enzyme - (a) into (b).

 

What is (a) and (b)? Select two answers below.

Image showing starch being broken down into maltose

CORRECT ANSWER
(a) Amylase
(b) Maltose
EDDIE SAYS
A good tip to remember is that most enzymes will end in the letters -'ase'. For example: Amylase Peptidase Lipase
  • Question 7

Other than the pancreas (not labelled in this picture), which part of the digestive system are proteases found in? 

 

Type two letters from the picture below.

Image of the digestive system

 

CORRECT ANSWER
C
D
EDDIE SAYS
C is the stomach and D is the small intestine. Remember, the three groups of digestive enzymes (carbohydrases, proteases and lipases) are all made in the pancreas as well.
  • Question 8

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 might we need glucose for? Select one answer below.

 

CORRECT ANSWER
Respiration
EDDIE SAYS
That was a tricky one! 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 9

Image of protein into amino acid by protease enzyme

Certain enzymes break up proteins in our food into amino acids. The amino acids will be reassembled into new proteins needed for growth and repair.

 

Which type of enzyme breaks up proteins into amino acids? Select one answer below.

CORRECT ANSWER
Protease
EDDIE SAYS
Amino acids join together to form different types of proteins like haemoglobin, keratin and other enzymes, so it's important we eat a variety of proteins.
  • Question 10

 Are the following statements true or false? Select one answer in each row.

CORRECT ANSWER
EDDIE SAYS
Don't forget: Proteases: Proteins → amino acids Carbohydrases: Carbohydrates → sugars Great work, you’ve completed another activity.
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