1. Organic Molecules

2. Organic Molecules The four major classes found in cells include:
carbohydrates
lipids
proteins
nucleic acids

3. Carbohydrates Monomers (building blocks) are monosaccharides
Polymers are formed by dehydration synthesis
Polysaccharides: many glucose molecules covalently bonded together
starch = plant storage carbohydrate

4. Iodine Test for Starch
In the presence of starch, iodine turns a dark purple, blue, or black color.
The regular form of the glucose chains in starch traps the iodine molecules.
Producing the dark color

5. Lipids Soluble in organic solvents and insoluble in water
Monomers (building blocks) = triglycerides (glycerol + 3 fatty acids)

6. Test for Lipids
Lipid based liquids leave stains (grease spots) behind when they dry and water based liquids do not.
This can be used as a test
Sudan IV is a lipid-soluble dye
In the presence of lipids, the solution turns red/pink

7. Protein Monomers = amino acids
Polymers are formed by dehydration synthesis between the amino group of one amino acid and the carboxyl group of a 2nd amino acid
Bond formed = a peptide bond

8. Biuret test for Protein
In the presence of protein, Biuret reagent reacts with the peptide bonds
A pink color indicates the presence of peptide bonds
The color intensity is related to the number of peptides bonds.
The depth of color represents the number of peptide bonds
Pink=few
i.e. peptide
Purple=more
Dark Purple=very many
i.e. polypeptide