This is my lab report on photosynthesis and cellular respiration. If you feel like it, read it and feel free to give constructive criticism. Its only supposed to be around 2 pages so I had to summarize alot of material.

June 5, 2008
Laboratory #5
“Photosynthesis & Cellular Respiration”

Photosynthesis is the method which most plants and algae convert carbon-dioxide, water, and sunlight into oxygen and sugars like glucose. For example, did you know that phytoplankton produce over half of the worlds oxygen supply? Photosynthesis occurs primarily within the chloroplast of the plants cells. Chloroplast are organelles which contain a light-absorbing pigment called chlorophyll that aids in photosynthesis.

Stage one involves the absorption of photons, and the splitting of water molecules (photolysis) to produce oxygen and hydrogen ions. These redox reactions are known as light reactions. The energy from the sun increases the electrons activity in the chloroplast membranes, known as thylakoids, moving them up the energy hill. While the splitting of water molecules produces oxygen and hydrogen atoms. Photosynthesis is a perfect example of the transfer of solar energy to chemical energy.

The second stage of photosynthesis are known as the dark reactions or the Calvin cycle. This is the stage where the energy from stage one is used to make food. Carbon Dioxide is fused with a sugar called RuBP (ribulose bisphosphate) with the aid of the enzyme rubisco. Products of the Calvin cycle include 3-6 carbon compounds that are broke down into 6-3 carbon compounds. One carbon compound is used to make G3P(glyceraldehyde-3-phosphate), which is then synthesized into glucose, leaving 5-3 carbon compounds. ATP is then used to make 3-5 carbon compounds which complete and start the cycle over.

Cellular respiration is the aerobic process by which plants and animals convert the chemical energy in food, to produce ATP. There are three stages of Cellular respiration, glycolysis, the Krebs cycle, and the energy transport chain.

Glycolysis is the first stage in cellular respiration. During glycolysis, a glucose molecule is split using ATP. The energy from the bonds of ATP is then released to break the bonds of glucose. The final product of glycolysis is 2 ATP, 2 NADH (nicotinamide adenine dinucleotide + hydrogen) , and pyruvic acid. The product will be used in the second and third stages of cellular respiration.

There is an intermediary stage which takes place in the mitochondria where pyruvic acid is combined with coenzyme A, the result is acetyl coenzymeA (which will be used in the Krebs Cycle) and carbon dioxide that is released into the bloodstream and eventually exhaled.

The second stage is known as the Krebs Cycle. In this stage, the acetyl coenzymeA combines with oxaloacetic acid to form citric acid. Citric acid is then synthesized into alpha-ketoglutaric acid. After losing a CO2 molecule, the alpha-ketoglutaric acid is split, giving a phosphate molecule to ADP to produce ATP. Alpha-keoglutaric acid then becomes succinic acid. Succinic acid then loses two hydrogen atoms to FAD, an electron carrier, these electrons are then transferred to the electron transport chain. Succinic acid then becomes malic acid. Malic acid is then transformed into oxaloacetic acid using NAD+. The cycle is then complete and begins again.

The third stage is known as the electron transport chain. In short, it is the diffusion of hydrogen ions, against a concentration gradient using the energy from electrons, across the inner membrane of mitochondria using the electron carrier, NADH, through the enzyme ATP synthase in order to make ATP. This process is called chemiosmosis. 34 ATP molecules will be made, with 10 NADH molecules producing 3 ATP and 2 FADH producing 2 ATP each, for a total of 36 ATP, including the ATP produced from
Glycolysis and the Krebs Cycle, minus 2 for active transport. The final step involves oxygen, the final electron acceptor, combined with protons to form water. These steps are known as the electron transport chain and are an important part of cellular respiration, whose final product is carbon dioxide, ATP, and water.

You really get this stuff. I'm taking my final in biology now (yesterday, today, and finishing Monday) and I really find it hard to understand all the stuff they want you to understand, like the cycles and processes.

The key is to learn the cycles and processes one at at time. You cant completely understand Mitosis after you just got through reading about the Krebs Cycle. You have to learn the Krebs Cycle before you can learn about Mitosis.

It may take you 30 minutes of reading and re-reading about the Krebs Cycle. It may take you an hour or two of researching and summarizing a particular subject, but once you've learned it, thats it. On to the next subject.

Another thing that really helps me is to attend the reviews and to have someone ask me questions over and over.

Once you can answer a question, you've got it.

I got the highest grade in my class on the Biology Exam.