Biology 2290F/G Final: Dean Exam Notes

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aquamarinehare26

18 Feb 2012

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-:-- - lamp (light [340-660nm] goes to diffraction grating [splits light like a. -:-- diffraction grating is also connected to lever and wavelength cam. -:-- spec 20 gives information on both the % transmittance and absorbance. glass prism] and then goes to exit slit, through sample, then detector) Spectrophotometer does not measure absorbance. measures the amount of light transmitted by a sample. -:-- when the wavelength is changed, you must adjust the spectrophotometer for the blank before reading each sample. Transmittance: fraction of incident light that passes through (is transmitted. -:-- t = i/io where io = radiant power of the incident light by) the sample. I = radiant power of light that passes through the sample. -:-- absorbance: amount of light absorbed by the sample. -:-- a = log (1/t) = log (io/i) Lambert"s law: for a thin layer of sample, the same proportion of light is absorbed regardless of the radiant power of incident light [io].

Related Questions

1.What was the purpose of measuring the stock solutionâs absorbance at different wavelengths? Or in other words, why did you need to make an absorbance spectrum for this dye?

2.Explain why you used a blank when using the spectrophotometer. Make certain to explain why you needed to use the blank between each measurement in the first part of the experiment, but only once in the second part of the experiment.

3.You mix up a stock solution of green dye by adding 5 mg of green dye in 100 ml of water and find that there is maximum absorbance of 0.75A at 425nm for this dye.

What wavelengths of light do you expect to be transmitted through this solution (refer to Table 3.1 in your lab manual)?

If you were to add another 2 mg of the green dye to your stock solution would you expect the absorbance at 425nm to be higher or lower than 0.75 A₄₂₅?

1. you carry out a serial dilution where you take 1 volume of solutionfrom a tube and dilute it with 5 volumes of water. what fold dilution are you carrying out?

2. bioloogically significant amino acids share a similar general structure. The variation in amino acids is found in?

3. which of the following assys relies on the reduction of copper from Cu(II) to Cu(I)

lowry

BCA

Bradford

all of these

4, suppose you are investigating vasopresin in the rat brain. which assays would be best for determining the concentration of vasopressin in the posterior pituitary gland?

5. which of the following statement is true about spectrophotometry:

absorbance and transmittance are inversely related

transmittance is measure on a log scale

absorbance equals transmittance

solution with absorbance value of 0.8 absorbs twice as much as one with absorbance value of 0.4

absorbance will be measured at 595nm in this lab

6.if you were given a saline solution consisting of 0.9gNaCl per liter your cell would:

swell and burst

remain normal

swell but not burst due to cell wall

crenate or shrink

ivoryhound489

Youâre trying to find the protein-concentration in an unknown sample using a spectrophotometer. The absorbance measurements for the standard curve gave a linear curve in the range 0.100 - 0.700. The measured absorbance for the unknown sample was 1.800. This means that the sample will have to be diluted again; how much and why? Can the mixture be diluted directly, or do you need a new sample?

Biology 2290F/G Final: Dean Exam Notes

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