Chapter 6, Problem 1Q

Summary Introduction

To analyze:

The inference that can be deciphered from the graph showing the relative fluidity of cell membranes in different species and whether the trend shown is apparent.

Given:

Researchers conducted an experiment to comparatively study the fluidity and composition of cell membranes. They maintained arctic sculpin at 0°C, a group of goldfish at 5°C, other group of goldfish at 25°C. They also maintained the desert pupfish at 34°C, and rats at normal temperature of 21°C. After keeping them for several days, the neuronal cells of all the animals were taken and membranes were isolated.

A fluorescent molecule was added to each of the extracted membranes and kept for some time at 20°C. Researchers then measured fluorescence and a graph was plotted by them. The graph depicted fluorescence against the body temperature of each of the animals.

The following graph shows the fluorescence of each animal depicted as colorful points at different temperatures. The more the value of fluorescence, the less will be the movement of molecules depicting a less fluid membrane.

The following table was drawn by the researchers showing the ratio of saturated-to-unsaturated fatty acids in the phospholipid phosphatidyl choline for different animals taken into consideration.

Introduction:

The membrane is fluid in nature and is responsible for the transport of various molecules in and outside the cell. The fluidity of the membrane depends on the temperature and unsaturation. The low temperature leads to increase in fluidity to cope up the temperature. The saturated fatty acids are those fatty acids which do not have any double bond and have no scope of addition of any molecule. They can only substitute the molecules. The unsaturated fatty acids are those which have one or more double or triple bonds that increase the fluidity of the membrane. The species that survive in lower temperature have more amounts of unsaturated fatty acids so that they can avoid being frozen and remain fluid for transportation of the molecules.

Explanation of Solution

The data in the graph shows the value of fluorescence in different species at different temperature. It was observed that when the temperature of the animal’s body is low as in the case of arctic sculpin, the value of fluorescence is also low. There is an inverse relation between the movement of molecules and value of fluorescence. The low fluorescence depicts the high movement of molecules in the artic sculpin showing that the membrane has greater fluidity. The greater fluidity of the membrane helps these organisms to withstand such low temperature. In contrast, the fluidity of membranes of rats is low as the fluorescence value shown in the graph is high. This indicates that fluidity of membrane is not as high as in the species of low temperature.

The data of membrane fluidity depends on the temperature of the animal and is apparent as the fluidity of the membrane will change according to the change in the temperature.

Conclusion

Thus, it was concluded that the post translational modifications are important for the proper protein functioning and deoxyribonucleic acid (DNA) of the protein decides whether the modification should occur or not. The trend shown in the graph is apparent.