The plasma membrane is the outer membrane of the cell which is selectively permeable. The small polar molecules and hydrophobic molecules can go through the lipid bilayer, but ions and large polar molecules cannot go through. There are some Integral membrane proteins present in the plasma membrane that enable ions to pass through the plasma membrane by active or passive transport.
Thus, the correct answer is integral membrane proteins. Ions generate electrochemical gradient so they are generally used in secondary transport systems.
Thus, the correct answer is integral membrane proteins.
<span>The minimal amount of nutrients needed every day by healthy people to prevent nutrient deficiencies is called the RDA. RDA stands for recommended dietary allowances. </span>RDA's are established by the Food and
Nutrition Board of the National Academy of Sciences. There is a term RDI related to this. RDI stands for recommended daily intake.