LAB SKILLS

 A.  Indicators:

BROMTHYMOL BLUE:

·        Used to identify the presence of CARBON DIOXIDE or acidity

·        Is blue, turns yellow/green in the presence of carbon dioxide/acid

·        When carbon dioxide is used during cell respiration, it returns to a blue color

 LUGOL’S SOLUTION / IODINE:

 ·        Used to identify the presence of starch

·        Is amber and turns purple/black when there is starch

·        During testing of a selectively permeable membrane, iodine indicates that the starch molecules remain in the dialysis tubing because they are too large to diffuse through the bag

 
 BENEDICT’S SOLUTION :

 ·        Used to indicate the presence of simple sugars/glucose/monosaccharides

·        IS blue, when heated up with the tested solution it turns to brick red

·        Used to test the movement of molecules through a membrane, if experiment worked correctly, the solution outside of the dialysis bag should indicate the presence of simple sugars.

 
CREATING A WET MOUNT

1. Place a drop of water on to the center of the slide.
2. Use tweezers to place the specimen at the center of the drop of water.
3. Carefully place the cover slip onto the slide at a 45 degree angle to prevent any air bubbles.

 CHROMATOGRAPHY

            Used to separate the pigments found in plants to trace evolutionary relationships.

 GEL ELECTROPHORESIS

Technique used to separate DNA or proteins into fragments to compare organism’s DNA fragments and to see evolutionary relationships, useful during investigation crime scenes.  Molecules separate based on molecular size, those largest remain at the top of the gel, where as those smallest travel to the bottom.  You must read across to see which sample of DNA is most closely related, by counting the number of bars.