1 of 47© Boardworks Ltd 2008 PHOTOSYNTHESIS. 2 of 47© Boardworks Ltd 2008 How do plants make their...

1 of 47 © Boardworks Ltd 2008

PHOTOSYNTHESIS


How do plants make their own food?

One of the raw materials that plants need to make food does come from the soil, the other comes from the air.

What are these two raw materials?

Plants use carbon dioxide and water to make their own food in a chemical reaction. What is the name of this reaction?

carbon dioxide(from the air)

water(from the soil)


What is the name of the process?

Plants make their food from carbon dioxide and water in a chemical reaction called photosynthesis.

Oxygen gas is also made as a by-product of photosynthesis.

glucose

oxygen



The food made by photosynthesis is the sugar, glucose.


Where does the energy come from?

Plants need energy for photosynthesis to take place. The energy for photosynthesis comes from the Sun.

Where in a plant does photosynthesis take place?

glucose

oxygen




Where does photosynthesis happen?

Plant cells in the upper surface of leaves have chloroplasts which contain the green pigment called chlorophyll.

It is chlorophyll, which absorbs light energy from the Sun, that enables plants to carry out photosynthesis.

glucose

oxygen



chlorophyll


Photosynthesis

Plants make their own food by a process called photosynthesis.

The word equation for photosynthesis

This equation can be read as:

“Carbon dioxide and water, using light energy and chlorophyll, react to make glucose and oxygen”

light energy

chlorophyll

carbon dioxide + water oxygen+glucose


What is needed for photosynthesis?


What is the word equation?


PhotosynthesisPhotosynthesisPhotosynthesisPhotosynthesis

Photosynthesis


• Water comes from the soil

• Carbon dioxide comes from the air

• Chlorophyll is a green pigment found in the chloroplast of leaves

It traps light energy that is needed to make the glucose

chloroplast contains

chlorophyll


The leaves are specially adapted for photosynthesis

1. Leaves are flat and thin

- To absorb maximum light

2. Leaves have tiny pores called stomata

- To allow CO2 in and O2 out

3. Leaves have chloroplasts

- These contain chlorophyll

- Chlorophyll traps light energy


The Products of Photosynthesis

1. Glucose

• Used in respiration• Stored as starch

2. Oxygen

• Used in respiration• Released into the air

– Animals then use it for respiration


To show that a plant produces starch

We need to show that a plant is making starch during the experiment

First we must remove any starch that is already in the plant i.e.

we must destarch the plant

To destarch a plant

It is placed in a dark cupboard for 48 hours

(The plant uses up all its stored starch and it cannot make any more)

During this experiment safety goggles must be worn!!!!!


1. Cover some leaves with aluminium foil

(This will act as our control)

2. Place plant in strong sunlight for several hours

3. Remove leaves from plant and boil for one minute to kill them


3. Place leaves in alcohol to remove chlorophyll

3. Now place leaves in warm water to soften

4. Place leaves on white tile and add a few drops of iodine


Results

Iodine is a red/brown chemical

If starch is present it turns blue/black

Leaf Result Conclusion

Leaf covered in foil No colour change No starch found

Uncovered leaf Turns blue/black Starch has been made during photosynthesis


Testing a leaf for starchTesting a leaf for starchTesting a leaf for starchTesting a leaf for starch

Testing a leaf for starch


To show starch is produced


The Control


QuizQuizQuizQuiz

Quiz

Exclude Q2


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Wordsearch


Skool.ie lessonhttp://www.skoool.ie/content/skoool_learning/junior/lessons/science/plant_nutrition/flash/h-frame-ns6.htm

Skool.ie assessmenthttp://www.skoool.ie/content/skoool_learning/junior/assessments/science/plant_nutrition/flash/h-frame-ns6.htm

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