Starch Test in Plants

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Questions and Answers

What is the primary purpose of boiling the leaf in water for 10 minutes?

To enhance the color of the leaf for better visualization.

To remove chlorophyll from the leaf immediately.

To destroy the cell membranes, allowing substances to enter the cells. (correct)

To sterilize the leaf from any contaminants.

Why is alcohol used in the experiment after boiling the leaf in water?

To enhance the chlorophyll present in the leaf.

To cool down the leaf before the next step.

To extract chlorophyll, avoiding any masking of color changes. (correct)

To provide a safe medium for the iodine solution.

What safety precaution should be taken when using alcohol in this experiment?

Keep the alcohol away from boiling water to prevent evaporation.

Use a larger volume of alcohol for better results.

Wear gloves but not goggles during the experiment.

Ensure the room is well-ventilated and avoid open flames. (correct)

What is the significance of using a white tile to spread the leaf?

To provide a neutral background for better visibility of color changes. Signup and view all the answers

What does the addition of iodine solution to the leaf test for?

The presence of carbohydrates, specifically starch. Signup and view all the answers

What happens to the leaf after it is placed in the boiling tube with alcohol?

It becomes soft and unrecognizable. Signup and view all the answers

What is the final step after adding iodine solution to the leaf?

To record the color change indicating starch presence. Signup and view all the answers

What is a potential outcome if the leaf has not been properly boiled before testing?

The chlorophyll will enhance the color change of iodine. Signup and view all the answers

Why is it necessary to use a plant that has been in sunlight for several hours?

To ensure photosynthesis has occurred Signup and view all the answers

What is the primary purpose of boiling the leaf in water?

To destroy cell membranes Signup and view all the answers

Why must safety spectacles be worn during this experiment?

To protect from chemical splashes Signup and view all the answers

What is the purpose of using alcohol in the experiment?

To extract chlorophyll Signup and view all the answers

Why is the alcohol tube placed in hot water rather than directly over flame?

To prevent fire hazards Signup and view all the answers

What indicates successful chlorophyll extraction?

The alcohol turns green Signup and view all the answers

Why is the leaf returned to hot water after alcohol treatment?

To remove remaining alcohol Signup and view all the answers

What is the purpose of the white tile?

To observe color changes clearly Signup and view all the answers

Why are exactly 10 drops of iodine solution specified?

To standardize the test Signup and view all the answers

What safety precaution is most critical when handling alcohol?

Keeping away from flames Signup and view all the answers

Why must the leaf be completely submerged in water during boiling?

To ensure even heating Signup and view all the answers

What tool is recommended for leaf transfer?

Forceps or glass rod Signup and view all the answers

What is the expected result if starch is present?

Blue-black coloration Signup and view all the answers

Why is minimal alcohol volume recommended?

To minimize safety risks Signup and view all the answers

What alternative can be used instead of a Bunsen burner?

Hotplate Signup and view all the answers

Why must iodine contact be avoided with skin?

It is harmful Signup and view all the answers

What is the purpose of the insulating mat?

To prevent table damage Signup and view all the answers

Why must the chlorophyll be removed?

To see color changes clearly Signup and view all the answers

What indicates the experiment is ready for iodine testing?

Leaf is dry Signup and view all the answers

What should be recorded during the experiment?

Leaf color changes Signup and view all the answers

Study Notes

Starch Test in a Green Leaf

Preparation: The experiment starts with a plant that has been exposed to sunlight for some hours. A healthy leaf is selected.
Boil Leaf: The leaf is boiled in water for 10 minutes. This process breaks down the cell membranes, allowing other solutions to enter the leaf cells. A hotplate or Bunsen burner can be used to boil the leaf. Safety precautions should be followed, such as wearing safety glasses and being cautious with hot equipment.
Alcohol Treatment: The leaf is placed in alcohol (in a boiling tube) in a beaker of hot water for 10 minutes. This removes the green chlorophyll from the leaf cells, so any colour changes caused by starch will be visible. Avoid using a naked flame with alcohol.
Wash and Spread: The leaf is taken out of the hot water and alcohol, and washed in more hot water to remove the alcohol completely and make the leaf soft. Then spread the leaf out on a white tile.
Iodine Test: Ten drops of iodine solution are added to the leaf. This is the final test to check for starch. If starch is present, the leaf will turn a blue-black color. Iodine is harmful, so avoid contact with skin.

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Description

This quiz covers the practical procedure for conducting a starch test on a green leaf. It includes steps from boiling the leaf to observing the iodine reaction, providing a comprehensive overview of the experiment. Ideal for students studying plant biology and experiments in botany.