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The base cytosine (C) pairs with guanine (G), and adenine (A) pairs with thymine (T). A component of one nucleotide, called a base, forms a hydrogen bond with a complementary base on the opposite strand. Two strands of DNA pair by hydrogen bonding. This pairing endows nucleic acids with the ability to store, transmit, and retrieve genetic information. Two polymers with complementary nucleotide sequences can pair with each other. Collagen, from which gelatin is derived, is a poor source of essential amino acids-the amino acids that the body cannot manufacture and must receive from the diet.ĭNA and RNA are nucleic acids (polymers of nucleotides). Individual collagen molecules cross link to other collagen molecules to form tough collagen fibrils. Glycine is the only amino acid small enough to allow the polypeptides to pack (by hydrogen bonding) into a tight cable. The three polypeptides in a collagen molecule associate with their glycines all facing collagen’s center. Collagen contains many of these amino acids, but few bulky ones (e.g., phenylalanine).Įach helix contains three amino acids per turn, with glycine located at every third position.
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Glucose molecules can be added to starch by a condensation reaction. A starch macromolecule is a polysaccharide composed of thousands of glucose units. Glucose is a hexose, a sugar composed of six carbon atoms, usually found in ring form. Lipids are a diverse group of molecules, which come in a variety of nonpolymeric forms.Ĭarbohydrates include simple sugars (monosaccharides) as well as large polymers (polysaccharides). In proteins, the monomers are amino acids in carbohydrates, the monomers are sugars and in nucleic acids, the monomers are nucleotides. A polymer is a chain of similar subunits, or monomers, that are linked together by covalent bonds. In terms of overall structure, all macromolecules except the lipids are considered polymers. Four major types of macromolecules-proteins, carbohydrates, nucleic acids, and lipids-play these important roles in the life of a cell. For example, macromolecules provide structural support, a source of stored fuel, the ability to store and retrieve genetic information, and the ability to speed biochemical reactions. Gigantic molecules, called macromolecules, populate a cell and provide it with important functions for life. Although living cells are primarily made up of water, a number of other molecules are also abundant.