6/18/2023 0 Comments Hydrogen bonding![]() Most chemical reactions in our bodies are assisted by enzymes, which are proteins, that must have very precisely shaped binding sites in order to attach the chemicals they need to so that the reactions can occur. Proteins, for example, are shaped in part by their covalent bonds, shown here, but also by their hydrogen bonds, shown here. Hydrogen bonds also determine the shapes of many molecules in our bodies, and their shapes, in turn, control how they function. Water's hydrogen bonds, for example, help ionic compounds, such as this salt crystal, dissociate, or separate, in our body fluids, making ions, such as sodium and chloride, available for our cells to use. Physiology involves chemical reactions, and chemical reactions in our bodies occur in water. For example, water is loaded with hydrogen bonds that give it many unique characteristics, and our body fluids are largely water. Although they are weak, hydrogen bonds are essential for our existence. You shake a whole lot of hands, but rarely any one for a very long period. This is somewhat like being at a crowded party and meeting many people. That means that they form, release, and reform with that or another atom. But in general, hydrogen bonds are weaker than either covalent or ionic bonds. The strength of a hydrogen bond varies depending on to whom the hydrogen is bonding, which in our cells is typically oxygen or nitrogen. In truth, a hydrogen bond is not really a true chemical bond. Hydrogen bonds don't just form in water, though, they can form any time hydrogen is present in polar molecules. When multiple water molecules are in the same area, the slightly positive hydrogen atoms are attracted to nearby and slightly negative oxygen atoms from other water molecules, and a weak bond forms between them. These slight charges set the stage for hydrogen bonds. Oxygen takes on a slight negative charge because of its greater claim to the shared electrons, and the hydrogen atoms take on slight positive charges because of this imbalance. This causes a slight imbalance in the electrical charge across the molecule. But its electron is more strongly attracted to the oxygen and spends more time hanging out with the oxygen than it does with its own nucleus. Each hydrogen atom binds to oxygen by sharing its lone valence electron. Oxygen is much bigger, though, and has eight positive protons. Hydrogen is tiny, usually just a single electron and a proton. A water molecule has two hydrogen atoms and one oxygen atom. Recall that in polar covalent bonds, electrons are shared unequally between the atoms. A hydrogen bond is a weak bond that occurs only when there are polar covalent bonds in the area. Inter means between, so bonds between different molecules are called intermolecular bonds. Hydrogen bonds not only can occur within a single molecule as intramolecular bonds, as seen here, but they can also occur between different molecules. But hydrogen bonds provide another option. The polar covalent bonds hold the molecule together. For example, polar covalent bonds between two hydrogen atoms and an oxygen atom form a molecule of water. Intra means within, so bonds that occur within a molecule or compound are called intramolecular bonds. Those bonds allow atoms to join together to form molecules and compounds, so they are bonds that occur within a molecule or compound. Specifically, we will answer the following questions: What are hydrogen bonds, how do they form, and why are they important? In other lessons, we explored ionic and covalent bonds. In this lesson we will explore another type of chemical bonding, hydrogen bonding. ![]()
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