Starter Activity:

Draw a line down the middle of your show me board.On one side, you must write all the advantages of genetic engineering, and on the other, all the disadvantages – no notes!

Key Area 7

Photosynthesis

Photosynthesis

Learning Intention: We are learning the

overall process of photosynthesis.

Success Criteria: Be able to state what a

carbohydrate is.Be able to write the word equation forPhotosynthesis.

Watch and Listen

• Plants are Amazing!

Energy• All our energy comes from the sun.• Sun gives the energy to plants• They make it in to food• Plants pass its energy on to animals• We eat the animals or plants (to get energy)

Plant Cell

Plants and Light• Plants manufacture their own food in a

process called PHOTOSYNTHESIS.• When a plant carries out

photosynthesis it combines simple substances to make carbohydrates like glucose and starch.

• Photosynthesis is carried out in the leaves of a plant.

PHOTO SYNTHESIS (Light) (To build)

Photosynthesis• Sunlight is extremely important as it provides

the energy for plants to make their own food

• Cells in green plants make their own food in a process known as photosynthesis

• Photosynthesis is an enzyme-controlled process where light energy from the sun is trapped by chlorophyll and converted into chemical energy

• Chlorophyll is a green pigment (colour) found in disc-shaped structures called chloroplasts in green leaves

Carbohydrates• The food that a plant makes is called glucose.

• Some of this is used immediately as an energy source and the rest is changed into starch for storage

• Starch is a large and insoluble molecule so it cannot leave the plant cell.

• Glucose and starch are carbohydrates made up of the following elements:

carbon (C)Hydrogen (H)Oxygen (O)

Watch and Listen

• Photosynthesis Video Clip

While watching this clip, think about how

green plants affect the composition of

gases in the atmosphere.

Photosynthesis Photosynthesis EquationEquation

CarbonDioxide

+ Water Glucose+Oxygen

6CO2 6H2O C6H12O6 6O2

Raw MaterialsRaw Materials ProductsProducts

chlorophyll

Light energy

The process of photosynthesis converts light energy into chemical energy.

Photosynthesis

Learning Intention: We are learning the

overall process of photosynthesis

Success Criteria: Be able to state what a

carbohydrate isBe able to write the word equation

forphotosynthesis

Starter Activity:

On a show me board, using no notes, write out the photosynthesis word equation.Make sure you label the raw materials and products. Question - How do green plants affect the composition of gases in the atmosphere?

Photosynthesis

Learning Intention: We are learning howto test a leaf for the presence of starch

Success Criteria: Be able to take part inan investigation to prove that a leaf isphotosynthesising Be able to describe the experiment

carried outBe able to name the solution used to test

forstarch

Investigating Conditions Needed for Photosynthesis

• Before we can carry out investigations to find out the conditions required for photosynthesis, we need to know the process for proving that a leaf has photosynthesised

• What do you think we will test a leaf for?

Testing a leaf for starch

Important Points:• 1) We boil the leaf to remove the waxy coating so our stain can get inside the leaf• 2) We place the leaf in ethanol to remove the green colour so we can see the colour

change.

Method

1) Place the leaf in a beaker of water.2) Sit the beaker on a tripod stand and use a

Bunsen Burner to boil the water. 3) TURN OFF THE BUNSEN BURNER.4) Using tweezers, remove the leaf.5) Place the leaf in a boiling tube with ethanol.6) Place the boiling tube into the beaker of

water.7) Once the ethanol has turned green, remove

the leaf using tweezers and test for the presence of starch, using Iodine solution.

Set up your experiment

100 ml of water in 250 ml beaker

Proving that Light is Required

• Discuss with your partner how you think you can prove that light is required for photosynthesis to take place

• Your teacher will listen to all of your ideas

• You will then carry out an experiment to prove your hypothesis

Photosynthesis

Learning Intention: We are learning howto test a leaf for the presence of starch

Success Criteria: Be able to take part inan investigation to prove that a leaf isphotosynthesising Be able to describe the experiment

carried outBe able to name the solution used to test

forstarch

Starter Activity:What leaf (Q or R) would test positive for starch?Why?

Photosynthesis

Learning Intention: We are learning to use

skills we have already learned to carry out

an investigation

Success Criteria: Be able to carry out an

investigation to prove that chlorophyll is

required for photosynthesis

• Light energy from the sun is used by green plants to make their own food.

• Light energy is trapped by green pigment called chlorophyll

• Chlorophyll found in disc-shaped structures called chloroplasts

Chlorophyll

(green pigment)

Conditions Required for Photosynthesis

• You will now carry out the test for starch on a variegated leaf

• Write down your hypothesis.

Set up your experiment

100 ml of water in 250 ml beaker

Task

• Write up your experiment including your aim, variables, method and results.

• You must include a labelled diagram.

• You must include the reasons for boiling the leaf and for resting it in alcohol.

Photosynthesis

Learning Intention: We are learning to use

skills we have already learned to carry out

an investigation

Success Criteria: Be able to carry out an

investigation to prove that chlorophyll is

required for photosynthesis

Starter Activity:

Describe an experiment which shows thatcarbon dioxide is required for

photosynthesis.

You will need to use your knowledge from the

“testing a leaf” experiment.

Photosynthesis

Learning Intention: We are learning stage1 of photosynthesis

Success Criteria: Be able to name,describe and explain stage 1 ofphotosynthesis Be able to state the conditions required

forstage 1

Photosynthesis Song

PhotosynthesisPhotosynthesis

CarbonDioxide

+ Water Glucose+Oxygen

CO2 H2O C6H12O6 O2

Light energy

Raw Materials Products

Photosynthesis (stage 1)

• Photosynthesis happens in 2 stages.

• Stage 1 is the Light Reaction.

• It is sometimes called Photolysis.

Light energy

Light energy trapped by chlorophyll in chloroplasts

Water from roots

Excess Oxygen diffuses from the cell

water is split into oxygen and hydrogen

Hydrogen attaches to hydrogen acceptor molecules. Light energy is converted to chemical energy : ADP + Pi ATP.

Light Reaction

• Stage 1 is sometimes called photolysis.• Occurs in the chloroplasts.• Splitting of water into oxygen and hydrogen.• Oxygen is produced and excess oxygen

diffuses into the air. • Light energy is converted to chemical

energy in the form of ATP (ADP + Pi ATP).

• Hydrogen attaches to the hydrogen acceptor molecules.

• ATP and hydrogen are used in stage 2.

Task

• In groups, pupils should play a part in a short production to show their class what happens during the light reaction.

• Each person in the group must take part.

• You may use Show Me Boards or paper to help demonstrate the light reaction.

Photosynthesis

Learning Intention: We are learning stage1 of photosynthesis

Success Criteria: Be able to name,describe and explain stage 1 ofphotosynthesis Be able to state the conditions required

forstage 1

Starter Activity:Answer the following questions in your class

workjotter:

1) Name the two raw materials of photosynthesis

2) Name stage 13) Why is it sometimes referred to as the light-

dependant stage?4) What is the energy change that takes place?5) Name two products made in stage 1 that

are required for stage 2

Photosynthesis

Learning Intention: We are learning stage2 of photosynthesis

Success Criteria: Be able to name,describe and explain stage 2 ofphotosynthesis Be able to state the conditions required

forstage 2

Photosynthesis (stage 2)

• Photosynthesis happens in 2 stages.

• Stage 2 is called Carbon Fixation.

Hydrogen from stage 1ATP from stage 1

Carbon dioxide (from air)

Glucose formed

Carbon Fixation

• Stage 2 – sometimes referred to as temperature- dependent stage as it’s controlled by series of enzymes.

• ATP (from stage 1) provides energy for this process.

• Hydrogen from stage 1 combines with CO2 from the air to form glucose.

• The chemical energy in glucose is available for respiration or can be converted into other substances.

Task

• Take a full page of your notebook and draw the two stages of photosynthesis linked together.

Task

• In groups, pupils should play a part in a short production to show their class what happens during the whole process of photosynthesis.

• Each person in the group must take part.

• You may use Show Me Boards or paper to help demonstrate the process.

Consolidation TaskCollect a National 5 text book and readread pages 76 to 83.

You must complete:You must complete:Activity 7.1 working individually in your notebook, answering in FULL sentences.

You should complete:You should complete:Activity 7.2 working individually in your notebook, answering in FULL sentences.

You could complete:You could complete:Activity 7.3 working in pairs on A3 paper.

Photosynthesis

Learning Intention: We are learning stage2 of photosynthesis.

Success Criteria: Be able to name,describe and explain stage 2 of

photosynthesis. Be able to state the conditions required

forstage 2.

Starter Activity:

Answer on a show me board:Why is the glucose made in photosynthesis converted to starch?

Photosynthesis

Learning Intention: We are learning thedifferent uses of glucose in a plant cell.

Success Criteria: Be able to name the twocarbohydrates that glucose can be converted

to.Be able to explain why each of the

carbohydratesis suited to its function.

So . . .

• The final product is glucose.• We already know that glucose can be

converted to starch because starch is storage carbohydrate.

• Glucose can also be converted into cellulose, a structural carbohydrate – used to build cell walls.

PhotosynthesisSo what happens to the sugar made in the leaves?

It can be used in a number of ways

GlucoseGlucoseUsed as buildingMaterial (e.g. cellulosein cell walls)

Used immediatelyfor energy

Stored as starch and converted back when Sugar is needed byPlant

Starch

• A single starch molecule can be made up from around 200-800 glucose molecules.

• The glucose molecules are joined in coiled chains.

•

Comparing Starch and Cellulose

• Starch molecules and cellulose molecules are both large molecules.

• They are both built up from glucose.• This happens as a result of glucose

molecules being linked together in different ways.

• They have different structural arrangements and properties.

Starch continued…

• Starch molecules are large and insoluble in water.

• They act as concentrated energy stores.

• Starch is made of long coiled chains of glucose and stored in the form of a starch grain.

• Starch is called a storage carbohydrate.

Cellulose

• A single cellulose molecule is likely to be made up from around 1000 – 1500 glucose molecules.

• Cellulose is made up of chains of linear glucose molecules.

•

Cellulose continued…..

• Cellulose molecules are also insoluble in water and are not easily broken down.

• This makes them particularly suitable for use as a structural component of cell walls in plants.

• Cellulose is therefore known as a structural carbohydrate.

Photosynthesis

Learning Intention: We are learning thedifferent uses of glucose in a plant cell.

Success Criteria: Be able to name the twocarbohydrates that glucose can be converted

to.Be able to explain why each of the

carbohydratesis suited to its function.

Starter Activity:

On a show me board, using no notes, write down the three elements found in a carbohydrate.

Photosynthesis

Learning Intention: We are learning toinvestigate the limiting factors ofPhotosynthesis.

Success Criteria: Be able to name the three

limiting factors of photosynthesis.Be able to carry out an investigation tomeasure the rate of photosynthesis.

Photosynthesis

Photosynthesis CANNOT work without:

• Carbon dioxide• The correct temperature • Sunlight

If any of the above are in short supply they are said to be “Limiting Factors”.

Limiting Factors

• The three limiting factors of photosynthesis are: temperature, carbon dioxide concentration and light intensity.

• By increasing the limiting factors, you can increase the rate of photosynthesis and therefore, rate of plant growth.

Success CriteriaYour news/weather report must:• Be between 1 and 3 minutes long• Have a contribution from every group member • Contain the process of photosynthesis Your news/weather report should:• Be factually correct• Be spoken in a varied tone

Your news/weather report could:• Have interesting facts for your audience• Be entertaining, as well as informative

Garden Weather/News Report

Limiting Factors

• Discuss with your partner what would happen to the rate of photosynthesis if you increased the temperature to above its optimum.

• Why do very high temperatures cause the rate of photosynthesis to drop to zero?

• Think back to the enzymes topic.

Measuring the rate of photosynthesis

• This can be measured by: -rate of CO2 uptake -rate of O2 production -rate of build up of starch/carbohydrate

• The easiest of these to measure is O2 production in plants which live in water.

Pondweed Cabomba Elodea

• These plants produce tiny oxygen bubbles which are released into the water.

• This is good for the fish in a fish tank! What do the plants get from the fish in return?

Cabomba / Elodea bubbler

By counting the bubbles of oxygen released per unit of time, we can measure the rate of photosynthesis

Elodea Bubbler

X

Y

What could be limiting the rate of photosynthesis at point X?

What could be limiting the rate of photosynthesis at point Y?

Z

0.5 conc of CO2

250C

0.5 conc of CO2

150C

What could be limiting the rate of photosynthesis at point Z?

Elodea Bubbler

What happens as light intensity increases? The rate of photosynthesis increases then levels off.Why does it level off?Something else must be in short supply.

Elodea

• This animation helps demonstrate how limiting factors affect the rate of photosynthesis.

http://www.kscience.co.uk/animations/photolab.htm

Measuring rate of photosynthesis with Elodea

(pondweed)

elodea

Solution of sodium carbonate (a source of CO2)

Thermometer

lamp

funnel

Upside down test tube(to collect oxygen gas)

How could the light intensity be altered?How could the temperature be altered (and kept constant)?How could the CO2 concentration be altered?How can the rate of photosynthesis be measured?

Light intensity as a limiting factor

Light intensity

A

B

At A, low light intensity is limiting the rate of photosynthesis.

At B, light intensity is high, so another factor must be in short supply (carbon dioxide concentration or temperature).

Carbon dioxide concentration as a limiting factor

Carbon dioxide concentration

A

B

At A, low carbon dioxide concentration is limiting the rate of photosynthesis.

At B, carbon dioxide concentration is high, so another factor must be in short supply (light intensity or temperature).

Temperature as a limiting factor

Temperature (°C)

A

B

At A, low temperature is limiting the rate of photosynthesis.

At B, temperature is high, so another factor must be in short supply (carbon dioxide concentration or light intensity).

But what happens after 40°C?

400 20

Temperature as a limiting factor

• At very high temperatures, the rate of photosynthesis drops down to zero.

• Why do you think this happens? (Think back to the enzymes topic.)

Limiting factor graphs

• The temperature graph is different due to the enzymes that control photosynthesis being denatured at high temperatures.

Limiting Factors

Light Intensity

At this point, light intensity is the limiting factor

At this point, something other than light intensity is the limiting factor. It must be either CO2 concentration or temperature.

As a general rule,

whatever is on the x-axis is the limiting factor on the slope of the

graph.

What’s the limiting factor?Your teacher will add a label to the x

axis. You can then try to complete the sentences.

A

B At A, low ________________ is the limiting factor.

At B, ___________ or ______________ is the limiting factor.

Photosynthesis

Learning Intention: We are learning toinvestigate the limiting factors ofphotosynthesis

Success Criteria: Be able to name the three

limiting factors of photosynthesisBe able to carry out an investigation tomeasure the rate of photosynthesis