Today, the Railroad Retirement program is closely tied to the far better-known Social Security program, and although the Railroad Retirement program and Social Security share a number of common elements, key differences also exist between the two in areas such as funding and benefit structure.
The Cell Cycle. The cell cycle is the life cycle of a cell (Figure 5.3). At the end of the cell cycle, after mitosis has taken place, the parent cell no longer exists; it has given rise to two daughter cells. There are two phases in the cell cycle, interphase and mitosis.
ATP, a high energy molecule, is expended by working cells. Cellular respiration occurs in both eukaryotic and prokaryotic cells. There are three main stages of cellular respiration: glycolysis, the citric acid cycle, and electron transport/oxidative phosphorylation. Glycolysis. Glycolysis literally means splitting sugars. Glucose, a six carbon sugar, is split into two molecules of a three carbon sugar. Glycolysis takes place in the cell's cytoplasm. Glucose and oxygen are supplied to cells by the bloodstream. In the process of glyoclysis, two molecules of ATP, two molecules of pyruvic acid and two high energy electron carrying molecules of NADH are produced. Glycolysis can occur with or without oxygen. In the presence of oxygen, glycolysis is the first stage of aerobic cellular respiration. Without oxygen, glycolysis allows cells to make small amounts of ATP. This process is called anaerobic respiration or fermentation.