Biochemistry Lab - Quiz Flashcards
the fundamental chemical components of cells may be grouped into four basic categories
carbohydrates, proteins, lipids and nucleic acids
carbohydrates such as starch are detected by
mixing a sample with 2-4 drops of iodone or Lugol’s solution
if starch is present, the solution will turn from
yellow-brown color to dark purple
the color change in test for complex carbohydrates is due to a chemical reaction between
the large carbohydrate molecule and the iodine ions
carbohydrates such as starch are detected by mixing a sample with 2-4 drops of iodine or Lugol’s solution. The solution will turn from a yellow-brown color to dark purple if starch is present. The color change is due to a chemical reaction between the large carbohydrate molecule and the iodine ions. It is thought that the charged iodine ions are attracted to slight charges on the starch (polysaccharide) molecules, and this causes the color change.
Test for Complex Carbohydrates (Polysaccharides)
the presence of smaller carbohydrates like glucose can be determined by using
Benedict’s solution
has copper ions with a light blue color
Benedict’s solution
When Benedict’s solution is heated in the presence of sugars like glucose, the copper ions change and turn anywhere from
a light green to rusty orange-brown color
color if there is negative result in test for simple sugars (glucose)
blue
the presence of smaller carbohydrates like glucose can be determined by using Benedict’s solution. Benedict’s solution has copper ions with a light blue color. When Benedict’s solution is heated in the presence of sugars like glucose, the copper ions change and turn anywhere from a light green to rusty orange-brown color
Test for (Reducing) Simple Sugars (Monosaccharides)
The presence of proteins may be determined by mixing a solution with
Biuret test solution (or reagent)
is a mixture of copper ions, sodium hydroxide, and potassium sodium tartrate.
Biuret test
If proteins are present a chemical reaction occurs between the
copper ions and the protein molecules
The chemical reaction causes the Biuret test solution to turn from a _________________ if proteins are present
light blue to purple
what is the color if proteins are present/positive biuret test results
purple
what is the color if there is no presence of proteins/negative biuret test results
light blue
The presence of proteins may be determined by mixing a solution with. Biuret test is a mixture of copper ions, sodium hydroxide, and potassium sodium tartrate. If proteins are present a chemical reaction occurs between the copper ions and the protein molecules. The chemical reaction causes the Biuret test solution to turn from a light blue to purple if proteins are present
Test for Proteins
The presence of proteins can be determined using
Biuret Test
are fat-loving molecules that are colored.
Sudan Indicators
When testing a solution for lipids, there are two results one should be looking for:
a. Is there a separation of layers? (water & lipid)
b. Does the dye migrate toward one of the layers?
If the mixtures are all water soluble (no lipids present), then the Sudan IV will form
small micelles/droplets and disperse throughout the solution
A positive test result shows the
lipid layer sitting on top of the water layer, and the lipids layer will have a red-orange color
positive result in test for lipids has
2 layersand top layer is orange-red
negative result in test for lipids has
one layer and color is evenly distributed
The presence of proteins can be determined using Sudan III indicator. Sudan Indicators are fat-loving molecules that are colored.
When testing a solution for lipids, there are two results one should be looking for:
a. Is there a separation of layers? (water & lipid)
b. Does the dye migrate toward one of the layers?
If the mixtures are all water soluble (no lipids present), then the Sudan IV will form small micelles/droplets and disperse throughout the solution. A positive test result shows the lipid layer sitting on top of the water layer, and the lipids layer will have a red-orange color
Test for Lipids
is used for determining the presence of nucleic acids
(Dische) Diphenylamine Test
The presence of DNA will turn a
clear blue solution
what color is positive results in test for nucleic acids
blue
negative results in test for nucleic acids
clear color
it is used to spin small (2 ml or less) liquid samples at high speeds
micro centrifuge, microfuge
Test for Biomolecules: Protein
Biuret Test
Test for Biomolecules: Carbohydrates
Molisch Test
Test for Biomolecules: Nucleic Acids: DNA
Dische Test
Test for Biomolecules: Nucleic Acids: RNA
Orcinol Test
are a class of naturally occurring organic compounds that undergo a variety of chemical reactions
Carbohydrates
is general test for carbohydrates, compunds that are dehydrated by concentrade H2SO4 to form furfural or hydroxymethyl furfural will reach with alpha napthtol to yield a purple condensation product.
Molisch’s Test
Positive Molisch’s Test:
purple color complex
Negative Molisch’s test:
no purple color
is a specific test for reducing sugars or presence of free or potential aldehydes
Benedict’s Test
identifies reducing sugars, which have free ketone or aldehyde functional groups
Benedict’s test
Formation of a reddish precipitate within 3 minutes. Reducing sugars present.
Positive Benedict’s Test
No color change (Remains blue). Reducing sugars absent
Negative Benedict’s Test
No presence of reducing sugar
blue
has traces of reducing sugars
green/yellow
has moderate reducing sugars
oranged red
has large amount of reducing sugars
brick red
When Benedict’s solution and simple carbohydrates are heated, the solution changes to
orange red/ brick red
is a test used to distinguish between monosaccharides and dosaccharides
Barfoed’s Test
A positive reaction may be only a little dark red precipitate in the bottom of the test tube. If this appears within 2-3 minutes, it indicates a
monosaccharide
if a little dark precipitate does not appear or show after 10 minutes, ____________________ is indicated
disaccharide
