Photosynthesis Practical sheets

Photosynthesis Learning objectives: ◦ By the end of the lesson you should be able to:  Describe what the glucose made during photosynthesis is converted to.

Practical 1 Testing a leaf for starch

Introduction ___________ made in green plants by photosynthesis is stored in the form of _____________ Testing a leaf for starch is used to show whether of not ________________ has taken place The leaf will turn ___________ if starch is present. If starch is absent the leaf will turn _____________ Leaves need special treatment before this test can be carried out. Glucose Starch Photosynthesis Black Brown

Aim To carry out a starch test on a leaf

Method (a ) Leaf treatment StepReason Boil leaf in water for 5 minutes Heat destroys cell membranes and so allows iodine solution in. Use forceps to transfer leaf to a boiling tube containing alcohol Alcohol removes: Green chlorophyll, Waxy cuticle To let iodine in TURN OFF BUNSENAlcohol is flammable Place tube in the beaker of hot water. Leave until the leaf is discoloured. To boil the alcohol Starch test colour change will now be more visible. Remove the leaf and rinse in the beaker of hot water for 10 seconds Softens that the leaf can be spread out. Place leaf on a white tile and cover with iodine solution. The leaf will turn black if starch is present

Results What colour does the leaf turn? ________________________________ The leaf turns a black/brown colour

Conclusion What does the result show? ______________________________ That starch is present

Evaluation What safety precautions are taken in this experiment and why? __________________________________ ____________________________________ Eye protection is worn as liquids are being boiled Lit bunsen burners and ethanol are kept well apart as ethanol is flammable

REQUIREMENT FOR PHOTOSYNTHESIS Practical 2

Photosynthesis Learning objectives: ◦ By the end of the lesson you should be able to:  State the raw materials required for photosynthesis.  Describe how the raw materials get into the plant mentioning diffusion.  Write a word equation for photosynthesis.

Introduction The equation for photosynthesis is: Glucose is stored in leaves as ________. Co 2 Water Light Energy GlucoseOxygen Chlorophyll Enzymes starch photosynthesis starch If any one of the raw materials or requirements is missing, then ___________ cannot occur and ________ cannot be made

A variegated leaf has some white parts which lack ________________ Chlorophyll

Aim To show that chlorophyll, Co2 and light are essential for photosynthesis to occur.

Method 1. Your teacher will give you three leaves A – variegated and kept in the light B – kept in the light but without CO2 C – kept in the dark Draw an outline of each leaf in the “Before” column in your results table and label ◦ The green areas of leaf A 3. Test all the leaves using the method outlined in practical 1 4. Draw an outline of each leaf in the “After” column and label the areas of the leaf that have turned black

Results LeafAppearance Before Appearance After A B (No Co 2 ) C (No light) Interpretation Which leaf shows that for starch to be made by photosynthesis. a) light is necessary __________________ b) Co2 is necessary _________________ c) Chlorophyll is necessary ______________________________ Leaf C Leaf B Leaf A

Conclusion What requirements does this experiment show are needed for photosynthesis to occur? ___________________________________ Evaluation What is possible source of error in this experiment? _______________________________ Light, Co2 and Chlorophyll Keeping a leaf in a bell jar may also prevent CO2 reaching the leaf