Required practical 6 - Photosynthesis Flashcards
What is photsynthesis?
The process by which plants synthesise glucose using light energy from the sun.
Describe how you would investigate the effect if light intensity on the rate of photosynthesis in an aquatic plant
- Place cut pondweed in a boiling tube (containing sodium hydrogen carbonate solution) at a fixed distance from a light source.
- Count the number of bubbles produced in one minute using stop watch. Repeat again for a mean.
- Repeat several times at different distances/light intensities, and calculate a mean no. of bubbles for each distance.
- Plot a graph of rate of photosynthesis (bubbles per minute) (y) against light intensity (x).
Why is it best to use an LED light source rather than a lamp?
A lamp will emit more heat energy than an LED - therefore it may change the temperature of the experiment and affect rate of photosynthesis.
What is the relationship between the distance from a light source and light intensity?
Inverse square law states:
Light intensity is directly proportional to 1 / distance²
How can the measurement of oxygen production be more accurate?
If the pondweed is placed under a filter funnel with an inverted measuring cylinder over the spout, the volume of oxygen produced can be determined.
Why is sodium hydrogen carbonate solution used during this experiment?
It releases carbon dioxide, which is used by the pondweed during photosynthesis.
Why can the number of bubbles produced be used to calculate the rate of photosynthesis?
Oxygen bubbles are formed as a product during photosynthesis. The number of bubbles produced in a give time is proportional to the rate of photosynthesis.
