New
New
Year 10
OCR
Higher

The requirements and products of photosynthesis: practical

I can predict and investigate the presence of starch in the leaves of living plants kept in different conditions, and can explain my predictions and observations.

New
New
Year 10
OCR
Higher

The requirements and products of photosynthesis: practical

I can predict and investigate the presence of starch in the leaves of living plants kept in different conditions, and can explain my predictions and observations.

Lesson details

Key learning points

  1. Some of the glucose made by photosynthesis is converted into starch and stored in starch grains in leaf cells.
  2. Iodine solution can be used to test plant leaf tissue for the presence of starch.
  3. A scientific prediction is a testable statement about a possible outcome, which can be tested in an experiment.
  4. Predicting the iodine test result for destarched leaves kept in various conditions, and explaining the predictions.
  5. Observing the iodine test result for destarched leaves kept in various conditions, and explaining the observations.

Common misconception

Mixing up a prediction, an observation and an explanation.

This practical lesson explores predictions, observations and explanations in the context of using iodine solution to test leaves for starch.

Keywords

  • Photosynthesis - the process used by producers to make their own food via a series of chemical reactions

  • Glucose - a type of sugar, which is a simple carbohydrate

  • Starch - a complex carbohydrate, made of many glucose molecules joined together to form a polymer

  • Iodine solution - a reagent that can be used to test for the presence of starch

  • Prediction - a scientific prediction is a testable statement about a possible outcome, which could be tested in an experiment

For part 2, plants will need to be set up by the technician several days before the lesson; firstly to destarch them for 2 days in the dark, then to allow them to photosynthesise for 2 days in the light in various conditions.
Teacher tip

Equipment

Geranium, kettle, large beakers, heat-proof mats, boiling tubes, glass rods, forceps, ethanol, Petri dishes, white tiles, iodine solution, droppers, foil, bell jars, soda lime, marble chips, acid.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Cells in the leaves of plants have chloroplasts that contain a green pigment called .
An image in a quiz
Correct Answer: chlorophyll
Q2.
The energy required for photosynthesis is transferred to chlorophyll by ...
carbon dioxide.
chloroplasts.
Correct answer: light.
water.
Q3.
What is the correct word summary for photosynthesis?
Correct answer: carbon dioxide + water --> glucose + oxygen
carbon dioxide + oxygen --> glucose + water
glucose + oxygen --> carbon dioxide + water
glucose + carbon dioxide --> water + oxygen
Q4.
Some of the glucose made by photosynthesis is stored as starch. Which reagent can be used to test for the presence of starch?
An image in a quiz
Benedict’s solution
biuret solution
Correct answer: iodine solution
pH indicator
Q5.
Iodine solution changes colour in the presence of starch. What colour would you expect the iodine solution to be when starch is present?
Correct answer: blue/black
brick red
lilac/purple
yellow/orange
Q6.
Who correctly predicts what would happen if there was no carbon dioxide available for a plant during the day?
Lucas: This would have no effect on the amount of glucose made.
Correct answer: Izzy: No glucose would be made because photosynthesis needs carbon dioxide.
Laura: Carbon dioxide is just a waste product, so more glucose would be made.

6 Questions

Q1.
Some of the glucose made by photosynthesis is used to make a larger carbohydrate called , which is stored in grains in plant cells.
An image in a quiz
Correct Answer: starch
Q2.
The reagent called solution is used to test for the presence of starch.
An image in a quiz
Correct Answer: iodine
Q3.
True or false? The iodine test result for this leaf shows that it contains starch.
An image in a quiz
True
Correct answer: False
Q4.
Foil was attached to this leaf to block out the ...
An image in a quiz
ethanol.
iodine solution.
Correct answer: light.
water.
Q5.
Why is a leaf placed in hot ethanol when testing for the presence of starch?
An image in a quiz
To de-starch the leaf.
Correct answer: To remove green-coloured chlorophyll.
To turn glucose into starch.
To show the presence of starch with a blue/black colour.
Q6.
The photographs show the same leaf before and after the iodine method was used to test it for starch. Which statement explains why area A turned a darker colour during the test?
An image in a quiz
Area A had less chlorophyll so less starch was made.
Correct answer: Area A had more chlorophyll so more starch was made.
Area A had less carbon dioxide so less starch was made.
Area A had more carbon dioxide so more starch was made.
Q1 MarekMiś, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons

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