A] ORGANIC MOLECULES

• Organic molecules - carbon containing compounds produced by living organisms
• 4 major types of organic molecules: lipids, carbohydrates, proteins, nucleic acids

B] LIPIDS

• 3 Different types of lipids (based on molecular structure): 
  • triglycerides (fats & oils)
  • phospholipids (major component of cell membranes)
  • steroids (includes cholesterol & steroid hormones)
• Lipids are hydrophobic - they do not mix with water
• Triglycerides (fats & oils)
• very high in calories (per gram)
• saturation - the number of hydrogen atoms attached to each carbon in the molecule
• in general saturated fats are from animal origins, are solid at room temperature, and are closely associated with cardiovascular disease
• in general, unsaturated fats are from plant origins, are liquid at room temperature, and are not directly associated with cardiovascular disease
• melting point - the temperature at which the molecules change from a  solid to a liquid.  It is affected by:
• amount of saturation (more saturation - higher melting point)
• size of the molecule (bigger molecules - higher melting point)
• hydrogenation - the process of increasing the number of  hydrogen atoms attached to carbon atoms (increasing the saturation) in an unsaturated fat
• Emulsifier - chemical used to help mix lipids and water
• an emulsifier has both hydrophobic and hydrophilic properties (hydrophilic - a substance that mixes with water)
• common example: dish soap

C] CARBOHYDRATES

• These molecules are the most common fuel molecule for living cells
• Can be categorized as:
• monosaccharides - the carbohydrate monomer (building block)
• a simple sugar
• examples include: glucose, fructose, & galactose
• disaccharides - two monosacharides joined together
• a simple sugar
• examples include sucrose (table sugar) and lactose (milk sugar)
• polysaccharides - long change of sugar monomers; the carbohydrate polymer
• a complex carbohydrate
• examples include: starch and cellulose (also known as fiber)
• Benedict’s reagent  - chemical that reacts and changes color in the presence of most monosaccharides and disaccharides (excluding sucrose) but does not react in the presence of polysaccharides [negative test = sky blue; positive test = red orange to brown]
• Iodine (or Lugol's solution) - a chemical that reacts and changes color in the presence of starch (a common polysaccharide) [negative test = yellow to light brown; positive test = dark blue to black]

D] PROTEINS

• Proteins serve a wide variety of functions in living things, such as enzymes, some hormones, and structural components of tissues
• The monomers or building blocks of proteins are called amino acids
• Biuret reagent - chemical that reacts and changes color in the presence of protein [negative test = blue; positive test = pinkish purple]