Question

A pathogenic (disease-causing) E. coli bacterium living on a cold piece of dirty romaine lettuce in your fridge suddenly finds itself in the nice, warm, and cozy human intestine. How will this bacterium maintain the same level of membrane fluidity now that it's in a such a different environment?

		produce membrane lipids with hydrocarbon tails that are longer and have more double bonds
		produce membrane lipids with hydrocarbon tails that are longer and have fewer double bonds
		produce membrane lipids with hydrocarbon tails that are shorter and have more double bonds
		decrease the amount of cholesterol in the membrane overall
		reduce the amount of glycolipids in the membrane

Answer 1

Ans Produces membrane lipids with hydrocarbon tails that are longer and have fewer double bonds

At high temperature the membrane fluidity increases as the intermolecular forces between the membrane decreases compared to the kinetic energy of the phospholipid molecule. Thus, the membrane fluidity increases at high temperature and decreases at low temperature. To maintain the same level of membrane fluidity even at high temperature for the above pathogenic bacteria various modulation are adopted by the cell.

• The increases of cholesterol amount which tends to pull the phospholipid molecule together. Thereby increasing the intermolecular forces
• The membrane may have saturated or unsaturated fatty acid. The saturated fatty acid do not have double bond and arranged in compact manner which increases the intermolecular forces between phospholipid bilayer. The unsaturated fatty acid have done bond as a result the tails of phopholipid are crooked or kinked which decrease the interaction between them
• Thus, the membrane lipid which have fever double bond are more organized and compact. Thereby favoring increase molecular interaction between the phospholipid and maintains membrane fluidity even at higher temprature