Compounds Essential to Life

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Organic Chemistry/Biochemistry
1: Compounds Important to Life
• Biologists classify compounds into organic compounds and inorganic compounds.  Organic Compound: a compound that is derived from living things and contains carbon  Inorganic Compound: a compound generally derived nonliving things • Water

 Water is an inorganic molecule with unique properties that make it one of the most important compounds for living things.
 In the water molecule (H2O), the hydrogen and oxygen atoms bond so that the electrical charge is unevenly distributed.
 The area of the molecule containing oxygen has a slightly negative charge, and the areas containing hydrogen have slightly positive charges.
 Polar Compound: a compound with one side having a negative charge and the other side a positive charge
 Hydrogen bonds form between water molecules.
• Six Unique Properties of Water
1. Universal Solvent: Water is an excellent solvent due to its polarity. When ionic compounds interact with water, the compounds often break apart or dissociate into ions.
2. Surface Tension: Water’s high surface tension is due to the cohesion of its molecules. 3. Capillary Action: The ability of a liquid to move upward against the force of gravity by molecular attraction to a surrounding surface (adhesion).

4. Resistance to Temperature Change: When water is heated, most of the heat energy goes into breaking the hydrogen bonds between the molecules. Only after the bonds have been broken will the heat energy increase the motion of the molecules and thus raise the temperature of the water.

5. High Heat of Vaporization: At 100 °C & 1 atm, it takes 540 cal to change 1 g of water to vapor.
6. Freezing: The molecules of water move apart to maintain the maximum # of H bonds. Therefore, the density of ice (0.92 g/cm
3
) is less than the density of water (1.00
g/cm
3
).
• Carbon Compounds
 A carbon atom has four electrons in its outer energy level. Carbon readily forms four covalent bonds with other elements.
 Carbon bonds with other carbon atoms to form straight chains, branched chains, and rings.
 Because carbon can bond in such a variety of ways, organic compounds exhibit great variability. This variability is responsible for the great variation among living things.  Polymer: a compound consisting of repeated linked monomers  Monomer: a repeated, single-molecule unit in a polymer

 Macromolecule: a large biological polymer
• Condensation Reaction: a chemical reaction in which monomers are linked together to form polymers; water is produced
 Also called dehydration synthesis
 The reactants give off a hydrogen ion (H
+
) and a hydroxide ion (OH
-
), which in turn
combine to produce a water molecule (H2O)• Hydrolysis: the splitting of a polymer into monomers through a reaction with water  In hydrolysis a water molecule splits into a hydrogen ion and a hydroxide ion. As the polymer breaks apart, the hydrogen and hydroxide ions each combine with one of the monomers.

2: Organic Compounds
• For all living organisms, four types of organic compounds are essential: carbohydrates, lipids, proteins, nucleic acids.
• Carbohydrates: organic compounds composed of carbon, hydrogen, and oxygen in a ratio of two hydrogen atoms to one oxygen atom
 Monosaccharide: contains carbon, hydrogen, and oxygen in a ratio of one to two to one (simplest carbohydrate)
 General Formula = CnH2nOn
 Examples:
o Glucose: manufactured by plants during photosynthesis. Main source of energy for both plants and animals and is metabolized during cellular respiration. o Fructose: found in fruits and is the sweetest of the monosaccharides o Galactose: found in milk and is usually in combination with glucose and fructose  Glucose, Fructose, and Galactose have the same molecular formula (C6H12O6), but not the same structural formulas.

o Isomers: compounds that differ in structure but not in molecular composition.  Disaccharide:...
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