Protein In the Cell
Some 15 percent by weight of the total body is made up of protein. The membrane of animal cells represents an insoluble protein complex; the protoplasm contains soluble proteins and cytoplasmic bodies, which are to a large extent, insoluble proteins such as are found associated with mitochondria and microsomes; though microsomes also contain soluble proteins. Insoluble and soluble proteins are found in the nucleus.
Protein are found in all living cells, in single celled algae and bacteria and in multicelled man, and in substances known as VIRUSES, which may well represent the borderline between the living and the lifeless.
These proteins have many functions; they include maintaining osmotic integrity; storage for some particular element; enzymes, to catalyze, biochemical reactions, hormones to regulate metabolic processes (like insulin); carriage of molecular oxygen (like hemoglobin); the transportation of lipida (like lipoproteins).
The complexity of the protein is illustrated by their molecular weight. Whereas the molecular weight of glucose, a typical carbohydrate, is 180, that of a protein may vary anywhere from 10,000 to 10,000,000. From the point of view of elementary composition these protein contain the elements carbon, hydrogen, oxygen, nitrogen and sulfur, but their atoms in space.
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