Final Answer:
Lowering the temperature reduces the kinetic energy of phospholipids, causing the membrane to become less fluid (Answer: 2). This immediate effect impacts cellular processes dependent on membrane properties. Thus the correct answer is 2) The membrane becomes less fluid.
Step-by-step explanation:
When the temperature of a cell culture is lowered, the phospholipid molecules in the cell membrane undergo a decrease in kinetic energy. As temperature drops, the phospholipids within the membrane move less vigorously, leading to a reduction in membrane fluidity. This decrease in fluidity can impact various cellular processes, such as membrane permeability and the functioning of membrane-associated proteins.
The fluidity of a membrane is highly influenced by the nature of its lipid components. At lower temperatures, phospholipids tend to pack more closely together due to reduced kinetic energy, leading to a more solid-like state. Conversely, higher temperatures promote greater kinetic energy, causing the phospholipids to move more freely and increasing membrane fluidity. Therefore, in the scenario described, the immediate effect of lowering the temperature is a reduction in membrane fluidity.
It's essential to note that while this immediate change occurs, prolonged exposure to low temperatures might have more complex effects on membrane properties. However, the question specifically addresses the immediate impact, and the correct response is that the membrane becomes less fluid due to the temperature decrease.