Ap Bio Lab 5: Cell Respiration

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AP Biology Lab #5:
Cell Respiration|
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Brian Suarez
Completed with Yeonah Suk, Michelle Lee, and Agron
12/14/12
SBS21X (Period 1 & 2)
Ms. Brady

Brian Suarez
Completed with Yeonah Suk, Michelle Lee, and Agron
12/14/12
SBS21X (Period 1 & 2)
Ms. Brady

Introduction
To be able to carry on metabolic processes in the cell, cells need energy. The cells can obtain their energy in different ways but the most efficient way of harvesting stored food in the cell is through cellular respiration. Cellular respiration is a catabolic pathway, which breaks down large molecules to smaller molecules, produces an energy rich molecule known as ATP (Adenosine Triphosphate) and a waste product that is released as CO2. Basically, cellular respiration is a metabolic process that releases energy from organic compounds (such as C6H12O6) by metabolic chemical oxidation in the mitochondria within each cell. Proteins, carbohydrates, and fats can all be broken down into fuel for the cell but cellular respiration is usually correlated with glucose. Cellular respiration also requires O2 to carry out its pathway, as oxygen will act as a final electron acceptor. So, the final equation that can be represented for Cellular Respiration is: C6H12O6  + 6 O2  → 6 CO2 + 6 H2O + heat. Cellular respiration is divided into three different stages. Glycolysis, the first stage of cellular respiration, splits simple carbohydrates such as glucose into two molecules of ATP, two molecules of pyruvic acid, and two electron carried that have high energy that are known as NADH. This part of cellular respiration does not need oxygen, therefore ATP can be created by glycolysis, but it only makes a small amount and this method is not the most efficient method. The next stage in cellular respiration is the Citric Acid Cycle. This stage commences when the two pyruvate acids are converted into acetyl CoA. This pyruvate oxidation will produce 2 NADH and then the acetyl CoA will enter the Citric Acid Cycle. ATP is created during the Citric Acid Cycle will create 2 ATP molecules by substrate-level phosphorylation (which is made by enzymes) and molecules of NAD and FAD are reduced by electrons from the Acetyl CoA. The Citric Acid Cycle is called a cycle because the original molecules used to start the process, Oxaloacetate (with 4 carbon), is created again at the end of the process. This process is also where the CO2 is made. The proceeding stage is the Electron Transport Chain. This chain requires oxygen, directly. This occurs in the membrane of the mitochondria. The electrons are passed to oxygen and creates a proton gradient is formed and ultimately ATP is made. An important mechanism of cellular respiration is that is can control it’s rate of it. This pathway can be shut off or slowed down when the products of the reaction. In the case of cellular respiration, the ratio of ATP to ADP/AMP will tell the cell whether to speed up the process or to slow down the process. Because of the allosteric enzyme phosphofructokinase is in glycolysis, depending on the ratio of ATP to ADP/AMP, the process will be inhibited or not and because it is in the beginning of cellular respiration , it will affect the whole system. Cellular respiration can be measured in multiple manners; it can be measured in the consumption of O2, the production of CO2, and the release of heat or energy during the process. Questions that are asked during the lab is how the temperature of the water affects the rates of respiration of the peas and how the different peas will produce different amounts of oxygen and carbon dioxide. The hypothesis formulated during the lab was that only the germinating peas will consume the largest amount of oxygen and will convert the largest amount of CO2. Also, the temperature of the water will affect the rate of oxygen consumption in a direct proportion as in the higher the temperature, the higher the rate of consumption....
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