Bacteria are typically grown at a temperature of 37°C. When the temperature incr

Question

Bacteria are typically grown at a temperature of 37°C. When the temperature increases to 45°C the bacteria die.

A. What happens to the membrane of the bacteria at 45°C?

To test the effects of membrane composition on bacterial survival, different strains have been developed with the following changes. Specifically explain how each of these changes affect melting temperature (Tm) and whether the bacteria will now be more or less resistant to temperatures of 45°C. Be specific in regard to the physical effects and interactions within the membrane.

B. An increase in 18:3 (9, 12, 15) Linolenic Acid with a decrease in 18:0 Steric Acid

C. An increase in 20:0 arachidic acid with a decrease in 16:0 palmitic acid

D. The isomerization of cis 18:1 (9,) lipids to trans 18:1 (9) lipids.

Explanation / Answer

A. At 45 deg, the membrane becomes fluid due to rapid movements between the lipids. The structure , containing proteins and lipids, hence becomes unstable and collapses, killing the bacteria.

B. Tm will decrease as linolenic acid is unsaturated and has a lower melting point, and hence membrane will be more fluid. Fluidity proportional to ratio of saturated : unsaturated fatty acids

C.Tm will increase as FOR SATURATED FATTY ACIDS fluidity is inversely proportional to chain length. Arachidic acid has a longer chain than palmitate.

D. Tm will increase. cis FAs hava kink in their chains, like a stick partially broken in the middle with the two subparts attached at an angle. This will create unfavorable packing, and increase fluidity. Isomerization to trans fixes the kink, and more efficient packing will lead to better resistance and Lesser fluidity.

Related Questions

Navigate

• Browse (All)
• Browse B
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.