Bio 100 Section 11
Exam 1
I can consider myself as a fan of Cheerios, a cereal brands. I love cereal because of its taste and its nutrition. Whenever eating cereal, I always look at the nutrition facts table and feel great that I am eating good stuffs. However, I always wonder how cereal could help me to get away from hunger and not until Bio100, I still have that same question. Now, after learning about metabolism, I could know how cereal is transformed into energy. A sequence called metabolic pathways, which the products of a reaction are the reactants for the next reaction, has helped to make this happen. In general, in order to convert cereal we eat into energy, it must go through three different metabolic pathways: Glycolysis, Krebs cycle, and electron transport chain.
At first, when I consume Cheerios, it will be broken down to glucose molecules. However, glucose cannot be used by cells to get energy. Instead, glucose must be further converted to ATP, an energy form which can be used by cells. Glycolysis (literally meaning “sugar splitting”) is the first stage that glucose is converted to ATP. In Glycolysis, each glucose molecule is split into two 3-carbon sugars and consumed two ATP molecules to make this process. Each 3-carbon sugar molecule will yield two ATP molecules, therefore forming four ATPs. In total, they Glycolysis create two ATPs (created four ATPs but used two at the beginning. Two molecules of pyruvate – an organic acid - are also formed as a product of glycolysis.
In next metabolic pathway, pyruvate will be used as the reactant of the Krebs cycle to obtain cellular energy. Krebs cycle happens in the mitochondria and requires oxygen. In this sequence, two carbons from a pyruvate react with coenzyme A (CoA), and yield acetyl CoA. Then acetyl CoA adds two carbons to a 4-carbon oxaloacetate molecule, creating a 6-carbon citric acid molecule. Each turn of