Question

1. The concentration of an undiluted sample is 26.4 mg/ml. To calculate that answer, the concentration of the diluted sample was multiplied by the dilution factor. Knowing that the dilution factor is 2, work backwards to determine the concentration of the DILUTED sample.

	A.	13.2 mg/ml
	B.	132.0 mg/ml
	C.	1.32 mg/ml
	D.	26.4 mg/ml

What is the unit used to describe cell solutions measured in a spectrophotometer?

		Cells/milliliter
		Grams (g)
		Optical density (OD)
		Meters (m)

Spectroscopy is based on the ability of compounds to specifically create certain wavelengths of light.

true or false

You are reading chlorophyll a samples in the spectrophotometer at 665 nm. Which of the following absorbance readings are considered to be inaccurate?

		Abs 3.4
		Abs 2.7
		Abs 3.6
		Abs 2.1

Ideally, a standard curve should be a curved line, not a straight line.

True

False

which of the following are common uses for a spectrophotometer in a biology lab? There may be more than one correct answer.

	A.	To quantify the activity of an enzyme
	B.	To measure the concentration of protein in a cell sample.
	C.	To quantify the density of cells in a population
	D.	To quantify the amount of light-absorbing molecules in a sample.

Light with a wavelength of 600 nm is used to read the absorbance of microbial cell cultures because cellular compounds (proteins, DNA, chromophores) absorb light at this wavelength and therefore do not interfere with the measurement.

True

False

The spectrophotometer output is in what units?

		Absorbance (A or Abs)
		Nanometers
		Wavelengths
		None of the above

Carrots appear orange in color because they are reflecting what color of visible light?

		Orange
		Red
		Blue
		Violet

Answer 1

1) concentration of undiluted sample=26.4 mg/ml

dilution factor=2

concentration of the diluted sample= concentration of undiluted sample/dilution factor

= 26.4/2

= 13.2 mg/mL

A) 13.2 mg/mL

2) spectrophotometer measures the absorbance of the sample.

absorbance is the negative log ( percetage transmittance/100 )

optical density also measures the absorbance.

spectrophotometer measures c) Optical density (OD)

3) spectrophotometer measures the absorbance of certain wavelength of light, so the statement Spectroscopy is based on the ability of compounds to specifically create certain wavelengths of light. is false.