BIOL 150 1st Edition Lecture 4Chemistry Background (continued) H+ /O—H………O-l \ H H+Cl-Cl- Na+ Cl- Na+Cl-Covalent bonds, Ionic interactionsHydrogen bonds[DNA is held together tightly by Hydrogen bonds]Properties of atoms that form molecules- less than 4 tend to lose electrons — these will have more protons than electrons and will be positively charged ions- 4 or more tend to share electrons - 7 electrons tend to gain electrons — These will have fewer protons than electrons and will be negatively charged ionsWhat is an ion?- In sodium chloride (salt), sodium loses an electron and becomes positively charged, and chlorine gains an electron and becomes negatively charged.- The two ions are attracted to each other.- Sodium chloride (NaCl) dissolves in solution because the sodium (Na+) ions and chloride (Cl-) ions each become surrounded by water molecules.Water and Hydrogen bonds- Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion- Cohesion also helps the transport of water against gravity in plants- Water has a high specific heat - it can absorb heat before changing its temperature- HEAT is absorbed when hydrogen bonds break- HEAT is released when hydrogen bonds form - Ice floats because it is less dense than liquid water - WHY?- Why don’t most ponds or lakes freeze solid in cold winters?These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Water and Hydrogen Bonds- Molecules that can interact with water molecules (ex. molecules in the bloodstream or the soluble cytoplasm of a cell) are hydrophilic molecules- Molecules that do NOT interact with water molecules (ex. fatty acids, lipids, or proteins that will be found in membranes) are hydrophobic molecules.Example:H Hl / H—C—OH….Ol \H H