Photosynthesis Lab Report

Introduction

Photosynthesis is a process used every day by plants, algae, and some bacteria to harness light energy and turn it into chemical energy. Chloroplasts play a large role in the process, chloroplasts are organelles much like mitochondria that contain a double membrane and third inner membrane called the thylakoid membrane. It is on the thylakoid membrane where the process takes place. Chloroplasts contain their own DNA which is a major contributor to the stability of this organelle. Without this essential organelle the photosynthetic process would not be possible.

Chlorophyll is the pigment located inside the chloroplasts which gives the plants their green color. It is the substance that absorbs energy from light which excites

The DCPIP accepted the excited electrons passed through the photosystems and was reduced to DCPIPH.

While this process of reduction is taking place protons from water and DCPIP were being pumped into the lumen of the chloroplast. With the concentration of protons and electrons from the reduced DCIPH an electrochemical gradient is produced to create the production of ATP.

In week one of the experiment the effect of light and herbicide on the photosynthesis of chloroplasts was tested using the percent transmittance as a way of measurement. The first cuvette that was altered was the negative control which did not contain any chloroplasts, resulting in a percent transmittance that did not change. The second cuvette contained the chloroplasts and was not exposed to light. Since it was not exposed to light the percent transmittance was very low only increasing by about 1%. The third cuvette was the positive control which contained chloroplasts and was exposed to light. As expected this underwent a high percent transmittance because of the exposure to light. The fourth cuvette was exposed to light and contained chloroplasts and herbicide, a substance used to destroy unwanted plants. The percent transmittance was dramatically reduced compared to the positive control

Since herbicide inhibited the reduction of plastiquionone, electron transfer was reduced. Photosynthesis relies mainly on the transfer of electrons to form energy, which means that inhibiting the reduction of plastiquionone slowed the process of photosynthesis, which was evident by the greatly reduced percent transmittance. This same process was believed to be similar for the effect of insecticide on percent transmittance of photosynthesis. Insecticide is a substance commonly used on or around plants to stop insects from consuming and killing plants. It was hypothesized that insecticide would work in similar ways to inhibit the transfer of electrons in the photosynthetic electron transport chain. In an experiment done by R. Unteidt and M Blanke the effect of insecticide photosynthesis was tested on apple orchard trees. They found that insecticides had similar inhibiting effects as herbicides, inhibiting the transfer of electrons in photosystem II and I. slowing the phosphorylation which inhibits energy (Unteidt and Blanke, 2004). Along with this article and other research information the hypothesis, if insecticides are added to the chloroplast solution then the rate of percent transmittance would be reduced, was