Lab 6, 8 Flashcards
All living things are composed of
o Four basic classes of molecules: carbohydrates, proteins, lipids, and nucleic acid
Carbohydrates
– starch and sugar
Sugars
o Monosaccharide
o Simple molecules
o Made up of carbon hydrogen and oxygen
o glucose
Starches
o Long chains or polymers of simple sugars
o Polysaccharides
o amylose
How to detect the presence of different classes of molecules in solutions?
o By using specific agents
What to look for as an indication that a particular type of molecule is present?
o Change in color
What does it mean when the color changes?
o Test is positive for the presence of that particular molecule
How can we be sure that the physical changes we see are only due to the presence of the molecule?
o A control reaction is always performed for comparison
Distilled water in an experiment is an example of
o Control substance that provides a negative result
Testing for the presence of Starch in solution
o Add IKI solution 5 drops to 1% amylose
Adding IKI solution to starch will change the color from to?
o Brown to blue/black
o Positive
What solution to use when testing for sugar?
o 10 drops Benedict’s solution to 1% glucose
o Boil for 10 minutes
Adding Benedict’s solution to sugar/glucose will change the to color from to?
o Light blue to Orange means positive
Proteins
o Complex arrangements of amino acids
o Amino acids linked to each other in long chains
o gelatin
What solution to use when testing for protein?
o Biuret’s solution
o 1% gelatin
Adding Biuret’s solution to protein (gelatin) will change color from to?
o Light blue to pinkish purple
o Orange
Lipids
o Fats and oils
o Hydrophobic – does not mix with water
Fats
– solid at room temperature
Oil
– liquid at room temperature
Hydrophobic of lipids can be overcome by using what chemical and why?
o Bile salts
o Because they share both the properties of lipids and water (polarity)
