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The Role of the Leaf in Photosynthesis

This worksheet will explain how the leaves are used in photosynthesis.

'The Role of the Leaf in Photosynthesis' worksheet

Key stage:  KS 3

Curriculum topic:  Biology: Material Cycles and Energy

Curriculum subtopic:  Photosynthesis

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

The leaves are exceptionally important when it comes to photosynthesis. They are like factories which produce the food that plants need to grow and survive. But how?

Leaves are designed and adapted to allow photosynthesis to take place. They are flat and broad to capture as much of the light energy from the sun as possible.
 


They also contain lots of tiny holes called stomata which allow for the absorption of carbon dioxide and the release of oxygen.    

 

Do all leaves allow photosynthesis?

Surprisingly, no!  The only leaves that can photosynthesise are the ones that contain the chemical chlorophyll.  So how do you know what leaves contain chlorophyll? Easy, chlorophyll is the green pigment in leaves, so if a leave is green, it will photosynthesise.

 




Chlorophyll is the chemical responsible for converting light energy from the sun into chemical energy.  This chemical energy is then used to make glucose (C6H12O6) from carbon dioxide (CO2) and water (H2O).

Light energy   +  CO2  +   H2O   C6H12O6   +   O2

 

What happens to the Glucose?


The glucose produced in photosynthesis has a variety of uses. Some of the glucose is used to create other chemicals needed in the plant such as proteins. Some is converted into starch and stored in the plant for later use and some is used for respiration.

 

Respiration

Respiration is the process that all living organisms use to get the energy they need.  Plants use the glucose produced in photosynthesis and convert it into the energy needed for the living processes in green plants.

C6H12O6    +  O2        CO2 +   H2O   +   Energy

 

 


 

Experiment - Testing a leaf for starch

A simple experiment can be done to prove that green plants photosynthesise:

 




Step 1:   Boil the leaf in water for around 10 minutes to soften the leaf.  

Step 2:   Place the leaf in a boiling tube containing methylated spirit an heat for a further 10 minutes to remove the chlorophyll from the leaf (IMPORTANT: Make sure the bunsen burner is switched off before using the methylated spirit as it is highly flammable)

Step 3:   Rinse the leaf with cold water

Step 4:   Test the leaf with iodine.  If the plant has photosynthesised the iodine should turn from brown to blue/black, indicating the presence of starch.   



The white of a variagated leaf does not contain any chlorophyll. What would you expect to see happen when this type of leaf is tested for starch?

 

We will now answer some more questions on photosynthesis and the importance of leaves.

What is the name given to the tiny holes on the surface of a leaf that allow the transfer of gases to take place? 

chlorophyll

chloroplast

stomata

photosynthesis

What is the name of the green chemical in plants that converts light enery into chemical energy? Write the word in the answer box.

What is the chemical formula for glucose?

CO2

C2H2O2

C6H12O6

C12H22O11

Some of the glucose produced during photosynthesis is converted into storage for later use. What is the name of the storage chemical that glucose is converted into?  

carbon dioxide

sugar

starch

protein

What are the raw materials needed for respiration?

water

oxygen

starch

glucose

carbon dioxide

chlorophyll

Complete the word equation for respiration.

 

Glucose  +  ____A____  ---------->  Carbon dioxide  +  _____B_____  +  energy

 

Remember to write your answers in lower case.

 Answer
A
B

When using methylated spirit to test a leaf for starch, why is it important to ensure that there are no near by naked flames?

methylated spirit is highly flammable

methylated spirit is a solid and will melt

methylated spirit will burn through the leaf

methylated spirit is non-flammable

In the present of starch, iodine will change from red/brown to what colour?

yellow

orange

blue/black

green/blue

In the answer box below, write the word which completes this sentence:

 

The white of a variagted plant does not produce starch as it does not contain any  __________ .

  • Question 1

What is the name given to the tiny holes on the surface of a leaf that allow the transfer of gases to take place? 

CORRECT ANSWER
stomata
EDDIE SAYS
The tiny holes in the leaf that allow carbon dioxide in and oxygen out are the stomata.
  • Question 2

What is the name of the green chemical in plants that converts light enery into chemical energy? Write the word in the answer box.

CORRECT ANSWER
chlorophyll
EDDIE SAYS
The green chemical which gives the leaves their green colour and also converts light energy into chemical energy is chlorophyll.
  • Question 3

What is the chemical formula for glucose?

CORRECT ANSWER
C6H12O6
EDDIE SAYS
The chemical formula for glucose is C6H12O6.
  • Question 4

Some of the glucose produced during photosynthesis is converted into storage for later use. What is the name of the storage chemical that glucose is converted into?  

CORRECT ANSWER
starch
EDDIE SAYS
Glucose is converted into starch and stored in the plant.
  • Question 5

What are the raw materials needed for respiration?

CORRECT ANSWER
oxygen
glucose
EDDIE SAYS
The process of respiration involves glucose and oxygen being converted into carbon dioxide, water and energy.
  • Question 6

Complete the word equation for respiration.

 

Glucose  +  ____A____  ---------->  Carbon dioxide  +  _____B_____  +  energy

 

Remember to write your answers in lower case.

CORRECT ANSWER
 Answer
A
B
  • Question 7

When using methylated spirit to test a leaf for starch, why is it important to ensure that there are no near by naked flames?

CORRECT ANSWER
methylated spirit is highly flammable
  • Question 8

In the present of starch, iodine will change from red/brown to what colour?

CORRECT ANSWER
blue/black
  • Question 9

In the answer box below, write the word which completes this sentence:

 

The white of a variagted plant does not produce starch as it does not contain any  __________ .

CORRECT ANSWER
chlorophyll
EDDIE SAYS
Chlorophyll is the chemical which converts light energy into chemical energy. Without chlorophyll a plant cannot photosynthesise.
---- OR ----

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