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Discuss the Process of Photosynthesis

In this worksheet, students will discuss the process of photosynthesis

'Discuss the Process of Photosynthesis' worksheet

Key stage:  KS 4

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

GCSE Boards:   Pearson Edexcel

Curriculum topic:   Plant Structures and Their Functions

Curriculum subtopic:   Plant Structures and Their Functions

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Virtually everything we eat can be traced back to plants. Either we eat food from plants or we eat food from animals that, in turn, have eaten plants. How do plants get their food then? Let's find out the answer to this question below.

 

Image of photosynthesis

 

 

Plants use sunlight to make their own food - this process is called photosynthesis. Plants contain a special green pigment called chlorophyll that traps sunlight. The chlorophyll is found in structures called chloroplasts, which are found in plant cells - mainly in palisade cells in the leaf.

Photosynthesis is an endothermic reaction because light energy is absorbed by the plant to power photosynthesis.  Enzymes speed up this process - without enzymes, the reactions in photosynthesis would happen really slowly. Water and carbon dioxide are also essential for photosynthesis. Water is absorbed by root hair cells in the plant's roots, and carbon dioxide enters the leaf of a plant through small pores called stomata (or stoma, when we're talking about just one).  Stomata are normally surrounded by guard cells that open and close. They control which gases enter or exit the leaf.

 

Image of leaf anatomy

 

 

Photosynthesis can be broken down into two main stages: 


 

First Stage:  Light energy is used to split water into oxygen and hydrogen. The oxygen is released into the atmosphere.

water   →  oxygen + hydrogen

 

Second Stage: The hydrogen is combined with carbon dioxide taken in from the atmosphere to make glucose

 hydrogen + carbon dioxide   →  glucose


 

The table below summarises the inputs (what is taken in) and outputs (what is released or produced) from each stage of photosynthesis:

 

Stage of Photosynthesis

 Input

Output 

First Stage

Light

Chlorophyll (structure)

Water (H2O)

Oxygen (O2)

Hydrogen (H2)

Second Stage

 

Hydrogen (H2)

Carbon Dioxide (CO2)

 

Glucose (C6H12O6)

 

The glucose made by photosynthesis is used for many processes:

 

It provides energy for respiration.

It is used to make cellulose - the main structural material in cell walls.

It is used to turn sugars, nitrates and other nutrients into amino acids which build up proteins.

It is stored as starch (in leaves, seeds, roots and tubers).

It is used to make fats and oils (energy stored in seeds).


In the following activity, you will explore the process of photosynthesis.

 

Glucose from photosynthesis is the starting point for the manufacture of materials that plants need to survive.

 

How is glucose used by the plant?

Column A

Column B

Used to make cellulose which is...
...for respiration
Stored as starch for example in...
...the main structural material in cell walls
Used to turn sugars and nitrates...
...leaves, seeds, roots and tubers
Provides an energy source...
...and oils often stored in seeds
Used to make fats...
...into amino acids which build up proteins

 

Photosynthesis occurs over two stages. 

 

Explain what happens in these two stages.

Column A

Column B

In the first stage of photosynthesis, light energy...
...with carbon dioxide to make glucose
The oxygen is released...
...into the atmosphere
In the second stage, carbon dioxide is taken in...
...from the atmosphere
The hydrogen from the first stage is combined...
...used to split water into oxygen and hydrogen

Discuss the role of chloroplasts in photosynthesis.

 

Image of leaf anatomy

Chloroplasts contain a pigment called chlorophyll that absorbs sunlight

Chloroplasts contain root hair cells that absorb water

The water is used in the first stage of photosynthesis

This light energy is used to split water in the first stage of photosynthesis

 

Rosie and Tim are discussing photosynthesis in their science lesson. Rosie says that all a plant needs for photosynthesis are water and carbon dioxide. Tim agrees, but says chlorophyll and enzymes are needed too.

 

Explain why Tim thinks chlorophyll and enzymes are needed for photosynthesis.

Chlorophyll is needed to capture light energy used to split water into hydrogen and oxygen

Chlorophyll is needed to take in carbon dioxide

Enzymes speed up the reactions needed for photosynthesis

Enzymes are needed to split up light energy

Glucose can be used to form long chains. Some of these chains are used for cell walls and for storage.

 

 What are the names of these long chains?

Cellulose

Chloroplasts

Starch

Why is photosynthesis regarded as an endothermic process? 

Because energy is taken in to start the reaction

Because energy is released when starting the reaction

Because energy is not needed

What are some of the inputs and outputs of the first and second stages of photosynthesis?  

 

 Stage of Photosynthesis

 Input

Output 

First Stage

Light

Chlorophyll (structure)

A

Oxygen

B

 

Second Stage

 

Hydrogen

C

 

D

 

In an exam question, Sam wrote that enzymes don't have a part to play in photosynthesis, whereas Lenny wrote that enzymes speed up the reactions involved in photosynthesis.

 

Who's correct?

Sam

Lenny

They are both right

Jon says that for photosynthesis to occur, carbon dioxide and water are needed. He says that only glucose is produced. Jane says that he's wrong and that oxygen, as well as glucose, is produced. 

 

Who's correct?

Jon

Jane

Neither of them

Why are enzymes needed for photosynthesis?

They speed up the reactions needed for photosynthesis

They are turned on when there's sunlight

They are chemicals that slow down reactions

  • Question 1

 

Glucose from photosynthesis is the starting point for the manufacture of materials that plants need to survive.

 

How is glucose used by the plant?

CORRECT ANSWER

Column A

Column B

Used to make cellulose which is.....
...the main structural material i...
Stored as starch for example in.....
...leaves, seeds, roots and tuber...
Used to turn sugars and nitrates....
...into amino acids which build u...
Provides an energy source...
...for respiration
Used to make fats...
...and oils often stored in seeds
EDDIE SAYS
Were you confident with this one? If not, it might be a good idea to have a go at this question a few times to consolidate your knowledge. It is important to know all this stuff because the uses of glucose often comes up in exams!
  • Question 2

 

Photosynthesis occurs over two stages. 

 

Explain what happens in these two stages.

CORRECT ANSWER

Column A

Column B

In the first stage of photosynthe...
...used to split water into oxyge...
The oxygen is released...
...into the atmosphere
In the second stage, carbon dioxi...
...from the atmosphere
The hydrogen from the first stage...
...with carbon dioxide to make gl...
EDDIE SAYS
Many reactions occur during photosynthesis but are summarised in two main stages. In the first stage, light energy is absorbed and used to split water into its components - that is oxygen and hydrogen. The oxygen is not needed, so it is released into the atmosphere. In the second stage, the hydrogen created from the first stage is combined with carbon dioxide taken from the atmosphere to produce glucose.
  • Question 3

Discuss the role of chloroplasts in photosynthesis.

 

Image of leaf anatomy

CORRECT ANSWER
Chloroplasts contain a pigment called chlorophyll that absorbs sunlight
This light energy is used to split water in the first stage of photosynthesis
EDDIE SAYS
Many structures are needed for photosynthesis to occur. Chloroplasts contain the pigment chlorophyll, which absorbs the sunlight and enables the process of photosynthesis to occur. Chlorophyll also gives plants their green colour!
  • Question 4

 

Rosie and Tim are discussing photosynthesis in their science lesson. Rosie says that all a plant needs for photosynthesis are water and carbon dioxide. Tim agrees, but says chlorophyll and enzymes are needed too.

 

Explain why Tim thinks chlorophyll and enzymes are needed for photosynthesis.

CORRECT ANSWER
Chlorophyll is needed to capture light energy used to split water into hydrogen and oxygen
Enzymes speed up the reactions needed for photosynthesis
EDDIE SAYS
How did you get on with this one? It is important to understand the functions of these two chemicals. Both chlorophyll and enzymes play vital roles in the process of photosynthesis. Indeed, without these substances, photosynthesis couldn't occur!
  • Question 5

Glucose can be used to form long chains. Some of these chains are used for cell walls and for storage.

 

 What are the names of these long chains?

CORRECT ANSWER
Cellulose
Starch
EDDIE SAYS
There were two answers to tick here. Cellulose is needed to keep cell walls strong, thus allowing plants to grow upright. Glucose is stored in the plant as starch, so that plants will have access to it when they need it!
  • Question 6

Why is photosynthesis regarded as an endothermic process? 

CORRECT ANSWER
Because energy is taken in to start the reaction
EDDIE SAYS
Can you remember these terms - exothermic and endothermic? An endothermic reaction is one that takes in energy from the surroundings - in photosynthesis, light energy is taken in or absorbed. An exothermic reaction, on the other hand, gives out energy to the surroundings such as in burning coal on a fire (combustion). It is important to know the difference and to understand that photosynthesis is an endothermic reaction. You've reached the end of this activity. How do you feel about this topic now?
  • Question 7

What are some of the inputs and outputs of the first and second stages of photosynthesis?  

 

 Stage of Photosynthesis

 Input

Output 

First Stage

Light

Chlorophyll (structure)

A

Oxygen

B

 

Second Stage

 

Hydrogen

C

 

D
CORRECT ANSWER
EDDIE SAYS
In the first stage of photosynthesis, water is split up by light to produce oxygen and hydrogen. water → oxygen + hydrogen The hydrogen is then combined with carbon dioxide to produce glucose.
  • Question 8

 

In an exam question, Sam wrote that enzymes don't have a part to play in photosynthesis, whereas Lenny wrote that enzymes speed up the reactions involved in photosynthesis.

 

Who's correct?

CORRECT ANSWER
Lenny
EDDIE SAYS
Well done if you went with Lenny! Without enzymes, the reactions involved in photosynthesis would occur very slowly, if at all.
  • Question 9

Jon says that for photosynthesis to occur, carbon dioxide and water are needed. He says that only glucose is produced. Jane says that he's wrong and that oxygen, as well as glucose, is produced. 

 

Who's correct?

CORRECT ANSWER
Jane
EDDIE SAYS
Well done if you went with Jane! Oxygen is one of the main waste products of photosynthesis. It may be a waste product for the plant because it doesn't need it, but this oxygen is essential for animals and any microorganisms that use oxygen for respiration.
  • Question 10

Why are enzymes needed for photosynthesis?

CORRECT ANSWER
They speed up the reactions needed for photosynthesis
EDDIE SAYS
Enzymes are catalysts, which means that they speed up reactions but without being used up in the process themselves. Without enzymes, photosynthesis would happen very slowly.
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