CHAPTER 2 CHEMICAL BONDS - Ionic bonds are electrostatic attractions between electrically charged atoms. These ions are called cations (+ charged) and anions (- charged). The attraction between these ions hold the bond together. This is a WEAK bond. • Most ionic compounds are in their dissolved (“solvated”) form because majority of the body is composed of water. ( Ex: Sodium Bicarbonate which is a major buffer in the human body is mainly found as a Bicarbonate Ion) • Hydroxyappatite is a very rare ionic compound that is found in its molecular (solid) form. It is a salt crystal made up of calcium, phosphate, and hydroxide. It is a salt crystal that makes bone hard!!! • When hydroxyappatite is found in its ionic/dissolved form, this is a sign of weak, brittle bones. - Covalent Bonds are formed by the sharing of electrons in two different atoms. Oxygen, Carbon Dioxide, Glucose, Fatty Acids, and Amino Acids are covalently bonded. Water is the most common example of a covalent bond. - Partial negative/positive charges in water is due to a polar covalent bond. - An ion or molecule with an unpaired electron in its outer shell is considered a Free Radical . These free radicals have a strong tendency to want to bind and they will steal electrons from things. Evidence shows that free radicals contribute to the aging process in humans because the stealing of electrons causes damage to tissues. Different kinds of Free Radicals - Nitric Oxide is responsible for vasodilation (makes a blood cell become larger in diameter). We have cells in our body that release this compound. It is a free radical, but it serves a positive purpose. - Superoxide Anion & Hydroxyl Anion are commonly used in white blood cells to kill bacteria. Cells can take up these free radicals and attack bacteria by pumping these free radicals and ripping the bacteria up, electron by electron. ( Ex: Neutrophils) - Vitamin E is a powerful antioxidant used to combat the aging process. - Electronegativity refers to how strong an element’s tendency is to pull electrons to the center of its nucleus. Molecules that are very electronegative have a strong affinity for electrons. (Ex: Oxygen) - Anything to the right of the periodic table is very electronegative. Anything closer to the left is less electronegative ( Ex: Hydrogen). - Water molecules have a dipole because Oxygen is an electronegative atom with partial negative ions and Hydrogen with partial positive ions. - Hydrogen bonds are the weakest of the three bonds, but collectively they are very strong bonds. • These bonds are responsible for the secondary structure of a protein making the protein functional. • They also hold the DNA (the most important structures of our body) together. • Hydrogen bonding can be considered an electrostatic interaction (NOT an ionic bond). The bonds technically have a partial negative/positive charge, but there is NO donation or acception of an electron.
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