Lab Exam #1
Which bags did osmosis occur?
Bag A, C, and D
What does bromcresol purple do?
it changes the pH, The low pH (acidic) form is yellow in solution and the high pH (basic) is purple.
standards
known concentrations that are used to determine the concentration of an unknown solution
How to calculate total magnification:
multiply the power of the eyepiece (usually 10x) times the power of the objective (4x, 10x, 40x)
How to use a spectrophotometer:
1. make sure to clean the tubes of free particles 2. turn on the spectrophotometer 10-15 minutes before lab 3. place a blank (a cuvette that contains only the solvent used to dissolve the chemical you are analyzing) 4. adjust the filter to the lowest wavelength and then adjust the wavelength until it is 0 5. remove the blank and add a tube with the chemical and solvent 6. continue and remember to put in the blank to make sure it is 0 7. adjust wavelength if needed
What reagent was used to test for sugars? What would you see if sugars were present?
Benedict's reagent test. It contains cupric ion complexes with citrate in alkaline solution. It will turn green to reddish orange (positive). A negative result is a blue color.
Bag B with 1% sucrose in a 1% sucrose beaker was....
isotonic, its weight stayed the same
Which contains more protein (C-N) bonds? Egg albumen or honey? How can you tell?
Egg albumen contains more proteins because it produce more of a violet color.
Which is a reducing sugar, sucrose or glucose? How do you know?
Glucose is a reducing sugar because it was red with Benedict's solution which means a lot of reducing sugars.
what is phenolphthalein and what did it do in the osmosis and diffusion lab?
It is a pH indicator that turns red in basic solutions. Since sodium hydroxide (NaOH) was in the beaker with a dialysis bag with phenolphthalein and water it turned PURPLE/PINK.
What is a Biuret test?
It tests long-chain polypeptides that have many peptide bonds. Blue is a negative result. Violets are positive results. It important to shake after each drop of Biuret is added.
What is the Sudan IV test used for?
It tests the solubility of lipids. It tests the ability to selectively absorb pigments in fat soluble dyes. There will be a red color in the presence of oil.
5 mL of 0.9% NaCl added to red blood cells
isotonic
What is a negative control?
No response is expected. This is usually water
Which contains more reducing sugars, potato juice or onion juice?
Onion juice contains more reducing sugar because it turned orange while potato juice turned green.
For which molecules and ions does the experiment give evidence for passage through the semipermeable membrane?
Phenolphthalein, Na+, OH-, pass through because they were small unlike starch.
Which colors more intensely, onion juice or potato juice? Why?
Potato juice colored more intensely because starch is more abundant in potato juice as a storage site for energy.
What is a positive control?
Reacts positively and shows what a positive result will look like.
Which reagent was used to test for starch? What would you see if starch was present?
The iodine test. It interacts with coiled molecules and becomes bluish-blackish. A yellow color is a negative test for starch.
What was the positive and negative controls of the Iodine Test procedure?
The negative control is distilled water. The positive control is starch solution.
What was the positive and negative controls of the Benedict's solution procedure?
The negative control is the distilled water plus Benedict's solution. The positive control is the reducing solution.
What was the positive and negative controls of the Biuret test procedure?
The negative control was distilled water and the positive control was protein solution.
standard curve
a graph showing a chemical's concentration versus its absorbance of a wavelength of light, and the relationship is a line
optimal buffer
alka-seltzer (~38 drops)
spectrophotometry
based on the principle that every atom, molecule, or chemical bond absorbs unique wavelengths of light, the spectrophotometer measures the amount of light absorbed and transmitted by a dissolved chemical
How to use a compound microscope: (???)
begin with 4 times objective and center the specimen, focus the object with the course adjustment knob, then go to 10 times and then 40 times and focus
5 mL of 30% NaCl added to red blood cells
hypertonic cells, crenate
Bag A with 1% sucrose in a 10% sucrose beaker was....
hypertonic, it lost weight because water flowed out of the 'cell'
5 mL distilled water added to red blood cells
hypotonic cells, lyse
Bag D with 25% sucrose in 1% sucrose beaker was....
hypotonic, it gained the most weight because water flowed in
Bag C with 10% sucrose in a 1% sucrose beaker was....
hypotonic, it gained weight because water flowed in
plasmolysis
occurred when 2-3 drops of 30% NaCl were dropped onto the Elodea leaf
Resolution
the ability to distinguish two objects from each other and show detail
Magnification
the ability to make small objects seem larger
transmittance
the amount of radiation passing through the sample
absorbance
the amount of radiation retained by the sample
