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Proteins and Enzymes

In this worksheet, students explore the role of proteins and enzymes in the function of the human body.

Key stage:  KS 4

Curriculum topic:  Biology: Cell Biology

Curriculum subtopic:  Enzymes

Difficulty level:  

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QUESTION 1 of 10

Proteins are polymers made of monomers called amino acids. There are only 20 natural amino acids, but they join in hundreds and thousands, creating long chains that make up different proteins. 

Proteins make up structural parts, like muscles, hormones, enzymes and antibodies. 

 

Enzymes are biological catalysts, which means they speed up reactions in the body. They are made in such a way so that reacting molecules can fit into them; this mechanism is called key-lock. The reacting molecules are called substrate molecules, and the place where they fit on the enzyme is the active site. This is illustrated in the following diagram:

 

 

Enzymes are 'denatured' in conditions of extreme temperatures and pH, i.e. they no longer work. There are, however, some exceptions to this rule, as we will see during the worksheet.

 

Enzymes also aid food digestion by breaking down food molecules. Amylase is found in the saliva and breaks down starch into sugars. Starch is a carbohydrate and all enzymes that break down carbohydrates are a carbohydrase. Proteases break down proteins into amino acids and lipases break down lipids (fats) into fatty acids and glycerol. 

What are the monomers that make up proteins?

amino monomers

amino acids

amino proteins

Select the two proteins from the options below:

DNA

hormones

muscles

skin

How many naturally-occuring amino acids are there? Type the number in the answer box.

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 2). Choose a statement that describes stomach enzymes after you study the diagram:

 

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 2

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

 

 

The optimum temperature for enzymes is 37°C, because this is the normal body temperature. Choose the statement that describes 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 are the monomers that make up proteins?

CORRECT ANSWER
amino acids
EDDIE SAYS
Proteins are polymers that are made of monomers called amino acids.
  • Question 2

Select the two proteins from the options below:

CORRECT ANSWER
hormones
muscles
EDDIE SAYS
Hormones and muscles are proteins.
  • Question 3

How many naturally-occuring amino acids are there? Type the number in the answer box.

CORRECT ANSWER
20
twenty
EDDIE SAYS
There are only 20 naturally-occurring amino acids.
  • Question 4

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

CORRECT ANSWER
catalysts
EDDIE SAYS
Enzymes are catalysts that work in living organisms; they are biological catalysts. This means that they speed up chemical reactions in the body.
  • Question 5

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

CORRECT ANSWER
substrate
EDDIE SAYS
Substrate molecules fit into the enzyme's active site, 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
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
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
Lipase breaks down fats (lipids) into fatty acids and glycerol.
  • Question 9

The environment in the stomach is very acidic (pH 2). Choose a statement that describes stomach enzymes after you study the diagram:

 

CORRECT ANSWER
the optimum pH for enzymes in the stomach is 2
EDDIE SAYS
The optimum pH for enzymes in the stomach is 2. 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:

 

 

The optimum temperature for enzymes is 37°C, because this is the normal body temperature. Choose the statement that describes what happens when the temperature increases above 37°C.

CORRECT ANSWER
enzyme activity falls rapidly as heat denatures the enzyme
EDDIE SAYS
Enzyme activity falls rapidly as heat denatures the enzyme.
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