A Cycle Is a Biological Pathway or Process in Which the End Product of One Cycle Becomes the Starting Point for the Next Cycles: Write an Essay About Cycles.

Topics: Cellular respiration, Adenosine triphosphate, Photosynthesis Pages: 3 (1000 words) Published: November 27, 2012
A cycle is a biological pathway or process in which the end product of one cycle becomes the starting point for the next cycles Write an essay about cycles.

Cells in the body use ATP as a direct source of energy. The conversion of glucose into ATP takes place during respiration. There are 2 different types of respiration, the more common and frequent one is aerobic respiration which is the production of ATP for energy. The less common one is anaerobic respiration, the production of lactate during which the muscles have a limited supply of oxygen, and however keep working despite this. Aerobic respiration requires oxygen and glucose present to work, and occurs in 4 stages: 1) Glycolysis- the splitting of a 6-carbon glucose molecule into 2 3-carbon pyruvate molecules. There is a net gain of 2 ATP’s produced. 2) Link reaction- the conversion of the 3-carbon pyruvate molecule into carbon dioxide and a 2-carbon acetyl co-enzyme A molecule. No ATP is produced during this stage. 3) Krebs cycle- the introduction of acetyl co-enzyme A into a cycle of oxidation-reduction reactions that yield some ATP and a large number of electrons. 4) Electron transport chain (ETC) - electrons used from Krebs cycle to synthesise ATP with water produced as a by-product. Glycolysis is the initial stage of aerobic respiration, and it takes place in the cytoplasm of cell. It is the breakdown of glucose into pyruvate, (which then goes in to initiate the second stage, the link reaction, and so forth) although there are a number of smaller enzyme controlled reactions for tis to take place. 1. Activation of glucose by phosphorylation. Before glucose can be split into 2 pyruvate molecules, it first must be made more reactive by the addition of 2 phosphate molecules, donated by the hydrolysis of 2 ATP molecules to ADP. This provides the energy to activate glucose. 2. Splitting of the phosphorylated glucose. Each glucose is split into 2 3-carbon molecules of...
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