The neutral theory of molecular evolution proposed that most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. Hence, in this model, most genetic changes in a population are the result of constant mutation pressure and genetic drift.
Answer:
The true statement is <em>Hydrophobic side chains are usually in the interior of the native structure</em>.
Explanation:
In the native structure of a protein, the hydrophobic side chains of aminoacids- such as leucine (Leu), alanine (Ala), methionine (Met), and others-are located in the interior of the structure. They are buried inside the structure, whereas polar side chains are exposed to the outside in the structure, and they interact with water molecules.
Regarding the other statements, entropy-as a measure of disorder of a system-is very important in protein stability as we know that native conformations are more ordered systems, with lower entropy and higher stability. Aminoacids in the protein structure interact each other through Van der Waals interactions and hydrogen bonds.
Answer:
It varies due to their polarities.
Explanation:
Remember, a membrane is a semi-permeable membrane. There are some substances that can cross the membrane and others have to take different route. It all comes down to their polarity. If we were to examine a membrane made of phospholipid bilayers, one side of it has hydrophilic heads and the inside has hydrophobic tails. The membrane is therefore polar, allowing polar substances to enter in and out of the cell. Non polar substances, such as water have to take a different route, through special proteins called aquaporins.