Question

The protein-synthesizing machinery was concentration of RNase. The sample was then subjected to sucrose gradient centrifugation. isolated from eukaryotic cells and briefly treated witha low The gradient was fractionated and the absorbance, or optical density (OD), at 254 nm was recorded for each fraction. The following plot (graph A) was obtained. Top Bottom Bottom What do the three peaks of absorbance in graph A represent? Label each one. a. The experiment was repeated except that, this time, the RNase treatment was omitted. Why is the centrifugation pattern in graph B more complex? What do the series of peaks near the bottom of the centrifuge tube represent? b. c. Before the isolation of the protein-synthesizing machinery, the cells were grown in low concentrations of oxygen (hypoxic conditions). Again, the experiment was repeated without RNase treatment (graph C). What is the effect of growing cells under hypoxic conditions?

The protein-synthesizing machinery was isolated from eukaryotic cells and briefly treated with a low concentration of RNase. The sample was then subjected to sucrose gradient centrifugation. The gradient was fractionated and the absorbance, or optical density (OD), at 254 nm was recorded for each fraction. The following plot (graph A) was obtained.

a) what do the three peaks of absorbance in graph A represent? Label each one.

b) The experiment was repeated except that, this time, the RNase treatment was omitted. Why is the centrifugation pattern in graph B more complex? What do the series of peaks near the bottom of the centrifuge tube represent?

c) Before the isolation of the proteins synthesizing machinery, the cells were grown in low concentrations of oxygen (hypoxic conditions). Again, the experiment was repeated without RNase treatment (graph c). What is the effect of growing cells under hypoxic conditions?

Answer 1

Ans a:

60S 405 80S 5 0 Fraction

Ans b: Absorbance of OD of proteins is a result of aromatic ring structures. Proteins are composed of 22 different amino acids from this only three amino acids contain an aromatic ring. Thus the presence of aromatic ring consisting of amino acid influence the OD of proteins

The series of peaks near the bottom of the centrifuge tube represent polysomes

Ans c:

Under hypoxic conditions, the cells grow faster, healthier, less stressed, and with less DNA damage