Photosynthesis

Background

Photosynthesis is the chemical process plants use to change energy in the form of sunlight into chemical energy in the form of sugar or other carbohydrates. The equation of this process is 6 CO2+ 6 H2O → C6H12O6+ 6 O2. Which is Carbon dioxide plus Water plus Light energy into Glucose plus Oxygen? For a plant to be able do the process of photosynthesis they need sunlight. In plants, photosynthesis usually happens in the leaves. This is where plants can get the materials for photosynthesis.

There are two reactions of photosynthesis, light dependent and light independent. The light-dependent reaction needs energy from the sun or other sources of light. The energy from sunlight is taken and used to break down the water that is absorbed into the plant through the roots. The water that is broken down makes oxygen, hydrogen, and electrons. These electrons move through chloroplasts make ATP. After that comes the second phase, the light dependent reaction, also known as the Calvin Cycle. The Calvin cycle doesn’t require light. The first part of the Calvin cycle is called carbon fixation. This is the process in which carbon dioxide joins with other organic molecules. Then the chemical energy stored in ATP and NADPH is transferred to 3-PGA molecules to form G3P molecules. Then the final step is the rubisco cycle. This process basically turns CO2 into glucose which is sugar.

The anatomy of leaves also relate to photolysis. In most plants, leaves are the major food producer for the plant. Structures within a leaf convert the energy in sunlight into chemical energy that the plant can use as food. Chlorophyll is the molecule in leaves that uses the energy in sunlight to turn water and carbon dioxide gas into sugar and oxygen gas.

Purpose

The Floating Leaf disk experiment is an excellent for students and people in general to learn and understand the basic process of photosynthesis. We also will understand the role of environmental factors in photosynthetic rate. This lab will also help us measure the effect of light and other factors on photosynthesis. This lab also investigates and explains the interrelated nature of photosynthesis and cellular respiration in the cells of photosynthetic organisms by breaking it down through leaves and allows us to visually see.

Hypothesis

If light produces more photosynthesis which produces more glucose and O2 causing it to float, than less light will produce less photosynthesis and cause the leaf disk to sink.

Materials

2-3 x fresh young leaves or about8 plant seedlings

2 x 5-cm sections of drinking straw

1 x small container such as cup or 100-mL beaker

2 x 250 mL-beakers

1 x 100 mL graduated cylinder

3 x 10 mL syringes

Baking soda/detergent solution (photosynthetic solution)

Water

Piece of aluminum foil

Procedure

Set up syringes

First take the 100 mL beaker mentioned in the material and add 35 mL of baking soda or detergent to it.(it may have already been done for you by your teacher if not proceed to do it)

Secondly use the cut up drinking straws to punch out 5 leaf disk. It is very important to make sure you avoid the mid vain of the leaf.

Thirdly remove the plunger from the syringe and blow the leaves out of the straw gently into the syringe. Then repeat the former two steps so you have total of 10 disks in the syringe.

After that is done replace the plunger slowly making sure to avoid crushing the leaf disk inside.

Once you have done that draw 8mL of the detergent or baking soda into the syringe. Then while holding the syringe up gently and slowly push the plunger up to remove the air from the syringe.

Then put your thumb over the tip of the syringe and pull the plunger. This will create a vacuum that will pull the gasses out of the leaf disk. Then hold the vacuum for 5 seconds, tapping the syringe to see if the leaf disk sinks. Then release the plunger and push the air out.

After that repeat steps 7 and 8 until the entire disk sink. Then place the syringe plunger down in the 250 mL- beaker while you prepare the other two syringes.

 Once you do that you that repeat steps 3-10 to set up two additional syringes with leaf disk.

Set up the experimental conditions and control

Wrap one syringe with foil to block out light. Take down notes in the data table for time 0.

Place the syringe wrapped in foil and one other syringe plunger in a 250 mL beaker an put the beaker under light. Place the third syringe in syringe in a beaker in a room light. Then take notice of any floating disk in the data table for time 0.