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7. Bioenergetics eLearn.Punjab

Procedure:
1. Fill about half of the 500-ml beaker with water.
2. Take some fresh branches of Hydrilla and place them in the broader side of a funnel and set

the funnel as shown in Fig 7.7.
3. Put an inverted test tube on the tubular part of the funnel. (Perform step 1, 2 and 3 by putting

all the apparatus in a water tub, so that no external air would enter the test tube. After step 3,
bring the set-up out of water tub.)
4. Put some quantity of potassium bicarbonate in the water of beaker.
5. Put all the set up in light and observe.

Observation:

Bubbles would be created in test tube water and these

will accumulate in the top portion of the tube.

Results: T

he branches have released oxygen gas in the form of

bubbles.

Confirmation:

When enough gas bubbles have accumulated in the

test tube, pick up the tube by putting thumb on its

mouth. Take a burning match-stick inside the tube. It

flares up when it touches gas bubbles. It confirms that

the test tube contains oxygen gas.

Error analysis:

The experimental work would not give the expected

results if any of the limiting factors of photosynthesis

i.e. light, CO2 , water, and chlorophyll are not present.
Similarly, if gas bubbles are not observed the branches

used may be dead and decayed.

Evaluation:

1. There are two phases of photosynthesis i.e. light Figure 7.7: Experiment set up for the demonstration of
reactions and dark reactions.During which of photosynthesis

these phases oxygen is produced?

2. Why was it necessary to do experiment with fresh

branches of Hydrilla?

3. Why did you use a burning match-stick for confirmatory test?

4. What products (other than oxygen) are produced during photosynthesis?

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