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Describe Enzyme Function

In this worksheet, students will describe enzyme function.

'Describe Enzyme Function' worksheet

Key stage:  KS 4

GCSE Subjects:   Biology: Single Subject, Biology: Combined Science

GCSE Boards:   OCR Gateway

Curriculum topic:   Cell Level Systems

Curriculum subtopic:   What Happens in Cells?

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Enzymes occur naturally in all organisms and are needed for many processes in the human body and in other organisms like plants. Enzymes are biological catalysts – they speed up the chemical reactions that take place inside all cells, but don't get used up in the process. Enzymes are protein molecules and are made up of amino acids. Most enzymes contain between 100 and 1,000 amino acids! These amino acids are joined together in a long chain,  which is folded to produce a unique 3D structure.
There are many different types of enzyme and each one catalyses a different reaction. 

Enzymes can be found inside the cell, for example in the cytoplasm, mitochondria, chloroplast (in plants) or nucleus. Enzymes found here help with different processes like respiration, DNA replication, metabolism or photosynthesis. 

Enzymes have a specific shape that allows molecules to fit in called the active site. It's here that large substances are broken into smaller molecules. 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 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

At low temperatures the reaction between enzyme and substrate is slow. Higher temperatures increase the reaction between the enzyme and substrate. However, too high temperatures can be problematic. Most enzymes have an optimum temperature, a temperature they work best at. At high temperatures the active site of an enzyme denatures. This means the active site changes shape permanently and substrates can't fit into the active site anymore. These substrates won't be broken down. Body temperature for humans is 37°C. If temperatures reach above 37°C the enzymes in the body will start to denature. Different organisms have enzymes that work best at different temperatures. 

Image of enzyme in high pH

The pH of enzymes surroundings can affect the way the enzymes active site is folded. This will mean it can become denatured. Different enzymes work best in different pH's. We say they have an optimum pH. Many enzymes work best in neutral pH (pH 7), whereas some work in acidic conditions while others work better in alkaline conditions.

In the following activity, you will describe enzyme function.

 

 

Image of plant photosynthesising

In order for plants to photosynthesise, enzymes are needed.

What often happens to the rate of photosynthesis at temperatures higher than 40°C? Select one answer below.

Increases

Stays the same

Decreases

Image showing enzyme in action

Enzymes can be found in the human body and help to 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...
matches the shape of specific substrates
The active site shape...
breakdown of the substrate
The fit between the enzyme and substrate is like.....
...have specific shapes
The enzyme catalyses the...
a lock and key

What is the common optimum pH for enzyme activity in humans? Select one answer.

Image of graph showing enzyme activity and pH

pH 1

pH 10

pH 7

Image of graph showing temperature and enzyme activity

The graph above shows enzyme activity at different temperatures.

At what temperature is enzyme activity lowest? Select two answers.

0-10°C

40°C

50°C

65-70°C

Enzymes are needed in the body for many different important processes. Select some examples below.

 

Photosynthesis

Respiration

DNA Replication

Digestion

The image below shows Enzyme A placed in a solution of high pH. What has happened to the active site of enzyme A? 

Image of enzyme in high pH

Complete the sentence:

The active site of enzyme A has...

Type an answer below.

The lock and key model illustrates how enzymes work.

Which substrate will be catalysed by the enzyme below? Type one answer below.

 

Image of enzyme and three different substrates

Energy is released in respiration. Enzymes are needed for respiration to occur. Which organelle contains the enzymes needed for respiration? Select one answer below.

 

Cell membrane

Nucleus

Mitochondria

Amy and Jodie are discussing enzymes in their science lesson. Amy says if plants are kept in extremely hot temperatures the plant won't be able to photosynthesise efficiently. Jodie agrees and says it's because the plant's enzymes might denature.

What does the term denature mean? Select two answers.

When an enzyme's active site becomes permanently changed

When an enzyme is against nature

When substrates will fit into an active site

No substrate can fit in the active site to become catalysed

What is the optimum temperature for respiration to occur in the human body? Select one answer below.

10°C

37°

100°

  • Question 1

Image of plant photosynthesising

In order for plants to photosynthesise, enzymes are needed.

What often happens to the rate of photosynthesis at temperatures higher than 40°C? Select one answer below.

CORRECT ANSWER
Decreases
EDDIE SAYS
The reactions involved in photosynthesis are controlled by enzymes. At really high temperatures, enzymes become denatured and the rate of photosynthesis decreases.
  • Question 2

Image showing enzyme in action

Enzymes can be found in the human body and help to 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 sub...
The fit between the enzyme and su...
a lock and key
The enzyme catalyses the...
breakdown of the substrate
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

What is the common optimum pH for enzyme activity in humans? Select one answer.

Image of graph showing enzyme activity and pH

CORRECT ANSWER
pH 7
EDDIE SAYS
Enzymes have different optimum pHs depending on where they're found in the body. Most cellular enzymes work best at pH 7.
  • Question 4

Image of graph showing temperature and enzyme activity

The graph above shows enzyme activity at different temperatures.

At what temperature is enzyme activity lowest? Select two answers.

CORRECT ANSWER
0-10°C
65-70°C
EDDIE SAYS
Enzymes don't work well at extreme temperatures. Very low temperatures mean that the enzyme and substrate don't collide and react. Very high temperatures mean that the enzyme's active site gets denatured.
  • Question 5

Enzymes are needed in the body for many different important processes. Select some examples below.

 

CORRECT ANSWER
Respiration
DNA Replication
Digestion
EDDIE SAYS
Bit of a trick question as the question asked "in the body" and though enzymes are needed in photosynthesis, this happens in plants!
  • Question 6

The image below shows Enzyme A placed in a solution of high pH. What has happened to the active site of enzyme A? 

Image of enzyme in high pH

Complete the sentence:

The active site of enzyme A has...

Type an answer below.

CORRECT ANSWER
denatured
denature
EDDIE SAYS
A solution's pH can affect the way enzymes are folded up and the enzyme's active site can become denatured. This means it won't be able to fit and catalyse any substrates.
  • Question 7

The lock and key model illustrates how enzymes work.

Which substrate will be catalysed by the enzyme below? Type one answer below.

 

Image of enzyme and three different substrates

CORRECT ANSWER
c
EDDIE SAYS
C is the only substrate that will fit correctly into the enzymes active site to be catalysed.
  • Question 8

Energy is released in respiration. Enzymes are needed for respiration to occur. Which organelle contains the enzymes needed for respiration? Select one answer below.

 

CORRECT ANSWER
Mitochondria
EDDIE SAYS
Mitochondria have a large inner folded surface area to allow more enzymes to help with the process of respiration. Without enzymes, reactions would happen at a very slow rate.
  • Question 9

Amy and Jodie are discussing enzymes in their science lesson. Amy says if plants are kept in extremely hot temperatures the plant won't be able to photosynthesise efficiently. Jodie agrees and says it's because the plant's enzymes might denature.

What does the term denature mean? Select two answers.

CORRECT ANSWER
When an enzyme's active site becomes permanently changed
No substrate can fit in the active site to become catalysed
EDDIE SAYS
When an enzyme has denatured it won't be able to catalyse any more substrates. That's because the substrates won't fit into the enzyme's active site anymore so important reactions will stop occurring.
  • Question 10

What is the optimum temperature for respiration to occur in the human body? Select one answer below.

CORRECT ANSWER
37°
EDDIE SAYS
37° is body temperature and the temperature at which all enzymes work best. If our body temperature rises really high because of illness our enzymes might denature, this could be very dangerous as important processes won't be able to occur.
---- OR ----

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