Related to hydrogen bonding is what are called van der Waals forces but van der Waals forces are even weaker than hydrogen bonds. Van der Waals forces attract neutral molecules to one another in the same way as is seen in hydrogen bonding. Because of the polarity of these types of molecules, the atoms that are more electronegative will attract atoms that are more electropositive. You can determine the electronegativity of a substance by looking at the periodic table. Those atoms in the upper right-hand corner of the table are considered the most electronegative.
CHEMICAL BUILDING BLOCKS OF LIFE There are four elements that make up the most common elements in living things. The largest contribution by weight is oxygen, followed by carbon, hydrogen, and nitrogen. Others that are less commonly seen include phosphorus, calcium, iron, and other metals or ions. There are four classes of biomolecules seen in the biochemistry of living things. These include lipids, carbohydrates, protein, and nucleic acids. As you will see, these tend to be polymers made up of certain monomers linked together. As you will see, when monomers turn into polymers, they do so by participating in dehydration reactions. Carbohydrates are molecules that are used for the storage and production of energy. Carbohydrates are made from sugars linked together. These molecules are the most abundant of the different biomolecules on earth. The simplest carbohydrate is called a monosaccharide. Two monosaccharides together will yield a disaccharide, while many together make a polysaccharide. They are made from carbon, hydrogen, and oxygen atoms only. A monosaccharide involves just a few different sugars. There are the six-carbon sugars, including glucose, fructose, and galactose, and five-carbon sugars, including ribose and deoxyribose. The five-carbon sugars are used to make RNA and DNA, respectively. Monosaccharides can be in an open-chain form or a closed-chain or “cyclic” form. Figure 6 shows the structure of several monosaccharides and disaccharides:
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