Agenda
• Turn in Pre-lab #4: Macromolecules
• Hand back Microworlds
• Lab Quiz #3 (pH)
MICROWORLDS HINTS
• Field Sizes
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40X = 5mm
100X = 2mm
400x = 0.5mm = 500μm
1000x = 0.2mm = 200μm
• State what you’re estimating the size of
• Label at least 2 structures
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More than 2 gives you a safety cushion
Animal cells don’t have a cell wall!
Bacteria don’t have a nucleus!
You can’t see & label most cells parts with 4x obj.
Microworlds
• Graded entries are in the grade book as a
score out of 20 points.
• Remaining entries will be out of 50 points.
• You do NOT need to turn in the graded entries
on the final due date.
Testing for Macromolecules
• Testing for the presence of
– Carbohydrates
– Lipids
– Proteins
– NOT nucleic acids
Testing for Carbohydrates
• Monomer = monosaccharides
– Glucose
– Fructose
• Disaccharide
– Lactose = glucose + galactose
– Sucrose = glucose + fructose
• Polysaccharide
– Starch (plants)
– Glycogen (animals)
Testing for Reducing Carbohydrates
• BENEDICT’S REAGENT
tests for the presence
of any monosaccharide
and some disaccharides
Testing for Carbohydrates
• BENEDICT’S REAGENT
tests for the presence
of any monosaccharide
and some disaccharides
• Does not detect all
sugars (sucrose)
• Dispose of Benedict’s
waste in appropriate
container
Testing for Carbohydrates
Detects Reducing Sugars
Monosaccharides
Testing for Carbohydrates
• Boiling water bath (with boiling chips)
– PLEASE NOTE THAT BOILING WATER IS HOT
– Wear goggles – solutions can boil out of tubes
• TUBE 1 = Glucose (positive control)
• TUBE 2 = negative control (?)
• Heat for 5 minutes and observe
Testing for Carbohydrates
• IODINE REAGENT tests
for the presence of
starch (what do we
know about starch?
Testing for Carbohydrates
• TUBE 1 = Starch solution from potato (positive
control)
• TUBE 2 = negative control (?)
• Add 3-4 drops iodine and observe
• NOTE: Iodine stains badly
Testing for Lipids
• PAPER TEST – paper will
become translucent in
the presence of lipids
(think KFC napkins)
• Do early so it has a
chance to dry (will take
15 minutes at least)
Testing for Proteins
• BIURET REAGENT reacts
with proteins to give a
light purple color
Testing for Proteins
• TUBE 1 = Egg Albumen (positive control)
• TUBE 2 = negative control (?)
• Add 1mL (about two droppers FULL) of Biuret
• Dispose of Biuret’s waste in appropriate
container
Testing for Macromolecules in Food –
OTHERS
• If liquid, test just like before
• If solid, mince up 1 cm3 and mix with 10mL
distilled water
• Test with:
– Benedict’s (reducing sugar)
– Iodine (starch)
– Paper (lipid)
– Biuret (protein)
Safety Precautions
• Wear GOGGLES at all
times when there are
people working with
hazardous chemicals
(Biuret’s and Benedict’s
Solutions)
• Wash your test tubes BEFORE you start – this
lab gets cross-contaminated OFTEN
• Wash out all test tubes using test tube brush
when you’re done, get the goo out! Put tubes
away upside-down in drawer to drain
• Make sure your tray is returned to its original
position & looks neat and clean up the food
table! No food scraps lying around.
• Attendance points today, but a penalty if you
leave a mess!