PEROXISOMES These are vesicular organelles that break down lipids and other chemicals through the act of oxidation. They can self-replicate and are heavily present in both the kidneys and the liver, where detoxification is important. They contain various oxidation molecules.
CELL JUNCTIONS These are the structures that connect cells to other cells so that tissues and organs can stay
together. There are three major kinds of cell junctions: A. Desmosomes—these are made from proteins and look like disks in the plasma membrane. There are protein fibers extending from the plasma membrane into the cytoplasm. These act as connection between cells that undergo a great deal of stress,
such as the heart muscle tissue and skin. B. Tight junctions—these are highly connective between cells, forming a bond that completely encircles the cells they connect. They do not allow material to filter between cells. Tight junctions are found in the digestive tract so that nothing goes past the cells other than the material that goes through the cells themselves. C. Gap junctions—these structures are actually slim tunnels that connect the cytoplasm of two cells next to each other. They consist of proteins known as connexons. The structures are so narrow that only small molecules and ions can pass from cell to cell. In addition, electrical impulses are allowed to go from one cell to another without interruption.
CELL METABOLISM Cell metabolism represents the sum of all of the chemical reactions that occur within the cell. There are two major cell reactions that take place that can be defined as part of the metabolism. Catabolic reactions or “catabolism” are responsible for breaking down or
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