experiment help...

[dg2008]

Start by reading Experiment 1 and then use your knowledge and understanding of the processes of photosynthesis and respiration and the properties of enzymes as biological catalysts to write the interpretation of the results for Experiments 2, 3 and 4 which follow. For each experiment your answer should be less than 200 words.

 

Experiment 1

Method

A fixed quantity of Elodea canadensis is placed underneath an inverted water filled funnel at 20 °C in a beaker of pond water. A bright light is shone on the beaker. After a few hours a collection of gas is apparent in the test tube as the water it contained is displaced. The experiment is left to run for a specific time (6 hours) and the volume of gas is recorded.

pond water gas collecting support to keep funnel off bottom bright lamp Elodea canadensis

 

Results

10 cm3 of gas have collected in the test tube; the gas is identified by simple tests.

 

Interpretation

In Experiment 1, the Elodea canadensis is photosynthesising. Light and carbon dioxide (dissolved in the pond water), and water are available to the plant and it is able to synthesise glucose by the process of photosynthesis. The gas produced is oxygen. The plant will also be respiring: that is reacting glucose with oxygen. Photosynthesis must be occurring at a greater rate than respiration, as there is net production of oxygen.

 

Experiment 2

Method

Experiment 1 is repeated but this time in the dark. The apparatus is left for the same amount of time as Experiment 1 and the volume of the gas is recorded.

 

Results

2 cm3 of gas have collected in the test tube, the gas is identified by simple tests and is found to be different from the gas obtained in Experiment 1.

 

Experiment 3

Method

Experiment 1 is repeated at a range of different temperatures. For each temperature the amount of gas produced over a fixed time period is measured and recorded. The data collected is used to draw a graph of the rate of gas production against temperature.

 

Results

Graph 1 A graph of rate of gas production (measured in cm3 h−1) against temperature for Elodea canadensis.

 

 

Experiment 4

Experiment 1 is repeated once again but this time carbon dioxide is bubbled into the water so the amount of dissolved carbon dioxide in the water is increased above the level used in Experiment 1. Results 20 cm3 of gas have collected in the test tube; the gas is identified by simple tests to be the same as the gas produced in Experiment 1.

 

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Experiemnet 2 is about respiration or dark reaction & carbon dioxide fixation?

 

Experiment 3 is talking about rate of reaction with increasing temp

 

experiemnt 4 is about in increase in Oxygen due to increase in Carbon Dioxide.