Write the balanced symbol equation for photosynthesis.

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

What does chlorophyll do?

It absorbs light energy for photosynthesis.

Why is starch good for storage?

It is insoluble, so it does not affect the water balance of cells.

What is cellulose used for?

To build strong plant cell walls.

So gases have a short distance to diffuse.

What is the job of the palisade layer?

It has many chloroplasts to absorb light.

Tiny pores that let carbon dioxide in and oxygen out.

How does a leaf test show starch is present?

Iodine solution turns blue-black.

Why is the leaf heated in ethanol?

To remove the chlorophyll so the colour change can be seen.

Why must ethanol be heated in a water bath?

It is flammable, so no naked flame.

PhotosynthesisIB MYP Biology: Flashcards

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Write the word equation for photosynthesis.

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Write the word equation for photosynthesis.: Carbon dioxide + water → glucose + oxygen (in light, with chlorophyll).
Write the balanced symbol equation for photosynthesis.: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Where in a plant cell does photosynthesis happen?: In the chloroplasts.
What does chlorophyll do?: It absorbs light energy for photosynthesis.
Why is starch good for storage?: It is insoluble, so it does not affect the water balance of cells.
What is cellulose used for?: To build strong plant cell walls.
What is glucose combined with to make proteins?: Nitrates from the soil.
Why are leaves thin?: So gases have a short distance to diffuse.
What is the job of the palisade layer?: It has many chloroplasts to absorb light.
What are stomata?: Tiny pores that let carbon dioxide in and oxygen out.
What controls the opening of stomata?: Guard cells.
How does a leaf test show starch is present?: Iodine solution turns blue-black.
Why is the leaf heated in ethanol?: To remove the chlorophyll so the colour change can be seen.
Why must ethanol be heated in a water bath?: It is flammable, so no naked flame.

Exam questions on Photosynthesis

A market gardener near Marrakech in Morocco grows spinach in sunny fields. The dark green spinach leaves make glucose in their cells using light energy, and the gardener wants to understand the process so that she can grow healthier plants.
Write the balanced symbol equation for photosynthesis.2 marks
Potato plants grow in cool, humid highland areas of Peru. During the growing season the leaves make large amounts of glucose. By harvest time, the underground tubers of the potato plants are full of stored food, but the leaves contain very little glucose.
Explain why the potato plants convert glucose into starch for storage in the tubers.2 marks
A student wants to show that chlorophyll is needed for photosynthesis. She uses a plant with variegated leaves, which have green patches and white patches. She keeps the plant in the dark for 48 hours, then in bright light for six hours. She then tests one leaf for starch with iodine solution. The green patches of the leaf turn blue-black, and the white patches stay orange-brown.
Describe how the student should test the leaf for starch after the six hours in light.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).