Question

Maintaining fluidity. A culture of bacteria growing at \(37^{\circ} \mathrm{C}\) was shifted to \(25^{\circ} \mathrm{C}\). How would you expect this shift to alter the fatty acid composition of the membrane phospholipids? Explain.

Short answer

Bacteria will increase unsaturated fatty acids to maintain membrane fluidity at lower temperatures.

Step-by-step solution

Understand How Temperature Affects Membrane Fluidity

The fluidity of the cell membrane is influenced by temperature. Higher temperatures increase membrane fluidity, while lower temperatures decrease it. In order to maintain proper function, the cell can adjust its membrane composition to counteract these changes.

Identify Strategies to Adjust Membrane Fluidity

Cells will often alter the fatty acid composition of their membrane phospholipids to maintain fluidity. To do this when moving to lower temperatures, cells may increase the proportion of unsaturated fatty acids as these have kinks in their structure that prevent tight packing, enhancing fluidity.

Predict Changes in Fatty Acid Composition with Temperature Drop

When the temperature drops from 37°C to 25°C, it is expected that the bacteria will increase the amount of unsaturated fatty acids in the membrane. This change offsets the reduced fluidity caused by the lower temperature, helping to maintain the optimal state for physiological functions.

Conclusion of Fatty Acid Adjustment

To maintain membrane fluidity at the lower temperature of 25°C, the bacteria will likely alter the fatty acid composition of their membrane phospholipids by increasing the proportion of unsaturated fatty acids. This allows the membrane to remain fluid and functional despite the temperature decrease.

Key concepts

Fatty Acid Composition

Fatty acid composition is a crucial factor that influences the characteristics of cell membranes. Cell membranes are primarily made up of lipid bilayers, and the types of fatty acids present in these lipids can determine how flexible or rigid the membrane is.
In response to environmental changes, such as a shift in temperature, cells can alter the fatty acid composition of their membranes to maintain optimal function.

• Saturated fatty acids, which lack double bonds, tend to pack tightly together, leading to more rigid membranes.
• Conversely, unsaturated fatty acids, which contain one or more double bonds, have kinks in their structure that prevent tight packing and thus increase membrane fluidity.

When a cell needs to adjust its membrane fluidity against changes, like a drop in environmental temperature, increasing the proportion of unsaturated fatty acids is a common strategy. This adjustment allows the cell membrane to stay fluid and functional.

Temperature Adaptation

Environmental temperature plays a significant role in dictating the fluidity of cell membranes, which is vital for cell function. Bacteria, for instance, need to maintain a certain level of membrane fluidity to survive sudden temperature shifts.
Imagine shifting from a warm environment at 37°C to a cooler one at 25°C. Such a temperature drop will reduce membrane fluidity, potentially affecting the cell's ability to function properly.
The main strategy cells use to adapt to lower temperatures involves modifying the lipid components of their membranes.

• They often increase the proportion of unsaturated fatty acids, which helps prevent the membrane from becoming too rigid.
• This change ensures that the membrane remains flexible enough to allow essential biological processes, like nutrient transport and signal transduction, to occur efficiently.

By understanding these adaptive mechanisms, scientists can appreciate how organisms maintain life under varying environmental conditions.

Unsaturated Fatty Acids

Unsaturated fatty acids are essential components that contribute significantly to the dynamics of biological membranes. They contain one or multiple double bonds in their hydrocarbon chains, which introduces kinks or bends.
These kinks prevent the fatty acids from packing tightly together, thereby increasing the fluidity of the membrane they reside in.

• The role of unsaturated fatty acids becomes particularly critical when organisms experience a decrease in environmental temperature.
• To counteract the potential decrease in membrane fluidity due to cold, cells increase the proportion of these unsaturated fatty acids.

This strategic inclusion helps maintain adequate fluidity, allowing the membrane to function effectively, even in cooler conditions.
Therefore, unsaturated fatty acids are key players in ensuring cellular resilience against environmental stressors, like temperature fluctuations.